THESIS
AN EXPERIMENT AlJ INVESTIGATION OF THE
EFFECT OF LOCATION AND.PROJECTION OF
SINGLE GROIN IN A BEND
MD. AB\,JOBAIDA
ANSARI KHAN
IN PARTIAL FULFILLMENT OF THE REQU IREMENTS fOR
THE DEGREEOE MASTER
.
OF SCIENCE IN ENGINEERING
I WATER RESOURCES)
BANGLADESH UNIVERSITY OF ENGINEERING
AND TECHNOLOGY,
DHAKA
AUGUST. 1983
11111111111\\1111\ \\ 1111\\\11111\\
#55770#
,
BANGLADESH UNIVERSITY
OF ENGINEERING & TECHNOLOGY
August 25, 1983
WE HEREBY RECOMMENDTHAT THE THESIS
PREPARED BY
MD. ABU OBAIDA ANSARI KHAN
ENTITLED
AN EXPERIMENTAL INVESTIGATION
LOCATION AND PROJECTION
AS FULFILLING
THIS
MASTER OF SCIENCE
OF THE EFFECT OF
OF SINGLE GROIN IN A BEND BE ACCEPTED
PART OF THE REQUIREMENTS FOR THE DEGREE OF
IN ENGINEERING
Supervisor
Member
Member
(WATER RESOURCES)
~.
(Abdul Hannan)
{~
~.c.~
Alam
(Khorshed
Member
(Md.
Head of the Department
~~
sha!llSU1ISlalII
~~
(Muhammad
sahj8:n
;/
ABSTRACT
I
This study was taken to investigate the effect of location and
projection of .single groin in a bend. The Hydraulics and River
Engineering. Laboratory of the Dep~rtment of Water Resources
~ngineering
of Bangladesh University of Engineering and Technology,
Dhaka, pr0vided required facilities for the study. Six test runs
were made, throe with sin~le groin placed at the centre of the bend
.,.•.
and the rest three with single gro~n placed at a distance of ten
percent of the average channel width upstream of the bend. The
projection of the groins were varied from~five percent to twentyfive percent of the average ch811nelwidth. These groins were placed
at the concave bank of the test channel when the channel achieved'
a quasi-stable nature.
It was observed that with the increase of groin projection ratio,
the downstream protected length increased when placement of the groin
was centrally located. Beyond projection ratio of seventeen percent,
the protected length decreased. For groins placed at ten percent
upstream of bend centre, same trond of variation of downstream
protected length was found. The maximum value of groin projection
ratio for maximum length .of d0wnstream protection in this case was
twenty three percent. The downstream protected length was found to
be higher for groins placed at bend centre. Strong statistical
correlations were obtained for both the cases.
\
•
.,
iv
The maximum depth of scour hole at the toe of the groin
was found to increase with the increase of groin projection
for groins placed both at the centre and at ten percent
upstr2am of the bend. It was also found that the scour area
increased with the increase of groin projection ratio. Good
statistical correlatirns were obtained for both the cases.
The trend obtained for variation of sCOur depth conforms
with the equations of Ahmf1d (2) and Hossain (20).
I
il
"
v
ACKNOWLEbGEMENTS
The-cuthor gratefully ac:mowledges his ~rofound gratitude and
indebtedness to Dr. Abdul Hannan, Professor, Department of Water
Resources Engineering and Dean, Faculty of Giyil Engineering,for
,his sincere help, encouragement, guidance and cO"-operation .throuR:h.'
~
.•.
out the experimental investigations and during the preparation of
this thesis.
The author expresses his sincere gratefulness to other
members of his research committee: Dr. M. Shahjahan, Professor
and Head, Department of Water Resources Engineering; Dr.-M.t.Alam,
Associate Professor of the same department and Mr •.M.S: I~lam,
Director General, River Research Institute of Bangladesh Water
Development Board, for their. valuable com~ents,criticisms
and
suggestions which greatly improved the report.
The ."uthor extends his duop appreciatior: to Mr. !.,minurRahman;
Mr. Liaquat Ali Khan and Mr. Abdul Matin for their help during. the
experimental investigations and the preparation of this thesis._
Very special thanks are extended to the staff of the Hydraulics
and River Engineering I,aboratory for their help and co-o.pe.ntion
:Ln
carrying out the experiment successfully.
Finally, the author thanks to Mr.M.Mofser
Ali for tak\itig.,g'Eoat
"
;'
care in typing the rough draft and final copy of the thesis.
vi
TABLE OF CONTENTS
PAGE No.
ABSTRACT
iii
ACKN01rILEDGEMENT
v
LIST OF FIGURES
ix
LIST OF TABLES
xii
NOTATION
1
1.1 General
1
1.2 Objective of the study
CHAPTER TWO
3
: REVIEW OF LITERATURE
4
2.1 Introduction
4
2.2 Channel pattern
4
2.2.1 Meandering channel
6
2.2.2 Theories of Meandering
7
2.2.2., Earth's rotation theory
7
2.2.2.2 Helicoidal flow theory
8
2.2.2.3 The concept of graded stream
8
2.2.2.4 Minimum energy concept
9
2.2. 2.5 Disturbance 'theory
10
2.2.2.6 ~namic
10
instability theory
2.2.3 Geometry of meandering channel
11
2.2.3.1 Meander bends
2.2.3.2 Deterministic approach for predicting
bed level in a bend
2.2.3.3 Stochastic apprnach for predicting bed
level in a bend
12
:i~.(,
12
14
TABL~ OF CO~TENTS (Contd.)
vii
PAGE No.
2.3 Stable alluvial channel
2.4
J3P"lk
15
stabilization me"'-':1ods
17
2.4.1 Groin
18
2.4.2 Classification of groins according to the
method and material of construction
18
2~~.3
Classification
21
,v
•
according to function served
2.4.4 Classification acco rding to the height of
groin below high water
2.4.5 Special types of groins
2.4.~ Functional de8~gn of groin
2.5 Scour
CH ArTER THREE
t09
of groin
I,ABO,]
tTORY SET UP AND Jl7EASURE~mNTS
3.1 Introduction
3.2.'1.Water suppiy system.
3.2.2 Flow measuring
"
device
tailwater tank
3.2.4 The sand bed
3'2',?
25
29
31
31
3.2 The alluvial sand bed flume
l:ne
24
26
2.5;1 Scour at the
3.2~3.
23
Flow entrance
3.2.6 The dry sand feeder
3.2.7 Initial channel
3.2.8 Discharge and Slope
3.2.9 Measurement
3.3 Experimental procedure
31
32
32:
33
33
34,
34
35
35
35
36
.,
T ABLE
.oF
CONTENTS (Contd •)
.'..
viii
rAGE No.
CHAPTER FOUR
RBSULTS AND DISCUSSION
40
4.1 Introduction
40
,L 2 Effect of groin on downstream length protr2ction
41
4.2.1 Effect of prOjection of groin on downstream
length protection
42
4.2.2 Effect of location of groin on downstream
ldngth protection
44
4.3 Effect of groin on bank erosiom
45
4.4 Effect of groin on the cross'-sectional area
and veloci ty
46
4.5 Scour at the toe of groin
47
4.5.1 and
Effect
of projection of ~~oin on the Scour area
pattern
47
4.5.2
•
Effect of projection of groin on the
scour hole
r1epth
of
48
4.5.3 Effect of sroin projeotion on scour constant,K
50
4.6 Comparison of predicted scour depth
51
CHAPTEP FIVE
COllTCLlTSION
AND RECOMMENDAm-r:ON
5.1 Conclusion
52
5.2 Recommendation ofor future ,study
52
54
REFERENCES
APrENDICES
55
Appendix - A Figures
60
Appendix - B Date Tables
105
-!
LIST OF FIGURES
ix
FIGURES
2.1
3.1
3.2
3.3
4.0
4.1
4.2
4.3
4.4
4.5
4.6
4.7
4.8
4.9
4.10
4.11
4.12
4.13
4.14
4.15
I'LGE No.
Different
types of groin
Exporimental
60
set up
61
Size distribution
Calibration
Detinition
of bed materials
62
curve for .dry sand feeder
63
sketch
64
Location of bank line, thalweg and deposition
for set up 1 (First bend)
65
Location of bank line, thalweg
for set up 1 (Second bend)
66
and deposition
Location of bank line, thalweg and deposition
for set up 2 (First bend)
67
Location of bank line, thalweg
for set up 2 (Second bend)
and deposition
68
Location of bank line, thalweg
for set up 3 (First bend)
and deposition
Location of bank line, thalweg
for set up 3 (Second bond)
and deposition
69
70
Location of bank line, thalweg and deposition
for set up 4 (First bend)
71
Location of bank line, thalweg
for set up 4 (Second bend)
and deposition
72
Location of bank line, thalweg
for set up 5 (First bend)
and deposition
Location of bank line, thalweg
for set up 5 (Second bend)
and deposition
Location of bank line, thalweg
for set up 6 (First bend)
and deposition
Location of bank line, thalweg
for set up 6 (Second bend)
and deposition
73
74
75
Scour pattern
arOund groin
(set up 1)
Scour pattern
around groin
(set up 1)
Scour pattern
around groin
(set up 2)
76
77
78
"
79
x
LIST OF FIGURES (Contd.)
FIGURES
4.16
'+'17
4.18
4.19
4.20
4.21
4.22
4.23
4.24
4.25
4.26
4.27
4.28
4.29
4.30
,
4.31
4.32
4.33
PAGE No.
Scour pattern arOUn(i groin (set up 2)
Scour pattern around groin (set up 3)
Scour pattern around groin (set up
3)
Scour pattern around groin (set up
4)
Scour pattern around ISroin (set up 4)
Scour pattern around groin (set up
5)
Scour pattern around groin (set up
5)
Scour pattern around groin (set up 6)
Scour pattern around groin (set up 6)
1J,aril"ti:oJil
of" cro SEl;-,S eci7i!on
after
placement of groin, set up 1QefoI'e"and
1 , section 1-1 ,
2-2 and 3-3
Variation of ero ss-section before and
after
placement of groin, set up 1 , section
4-4,
5-5, and 6-6
80
81
82
83
84
85
86
87
88
,C
Variation of cross-section beforo and
placement of groin, set up 2, section after
1-1 ,
2-2 and 3-3
7ariation of cross-. 9ction before [ ld
placement of groin, sot up 2, section after
4-4,
5-5 and 6-6
Variation of crass-section beforo and
placement of groin, SGt up 3, section after
181 ,
2-2 and 3-3
Variation of cro ss-section before and
after
placement of p'roin, set up 3, sectir)ll
4-4,
5-5 and 6-6
Variation of cross-section before and
placemcmt of groin, set up 4, section after
1-1 ,
2-2 and 3-3
Variation of cross-section bef'ore and
pTacement' ef groin, set up 4, section ai)ter
J.-4,
5-5 and 6-6
Variation of cross-section before and .,after
placement of ,g;ro
i'n, SGt up 5, section 1::-1
,
2-2 and 3-3
89
90
91
92
93
94
95
96
97
LIST
OF IHGURES
xi
(Contd.)
FIGURES
4.3~
PAGE No.
Variation of cross-Jection before ':'ld
placoment of groin, set up 5, soction after
4-4,
5-5 and 6-6
C
4.35
4.36
4.37
4.38
4.39
4.40
98
Variation of cross-section before and after
placement of groin, set.up 6, section 1-1 ,
2-2 and 3-3
99
Variation of cross-section before and
placement of £:roin, set up 6, section after
4-4,
5-5 and 6-6
100
Helationship bet-..reen
groin pro .iection and
downstream length protected
101
Relationship between groin projection and
scour area
102
Relationcllip between sco;].rCle;:lth
and groin
pi'ojection
Relationship between groin projection and
scour constant
{
'"
103
104
LIST
OF TABLES
xii
TABLEr
PAGE lYo
Data for set
up 1 ,
Section 1-1
105
2
Data for set
up 1 ,
Section 4-4
107
3
Data for set
up 2,
Section 1-1
109
4.
/
6
7
8
9
10
11
12
.
ilata for set up 2, Section
4-4
Data for set up 3, Section
1-1
Data for set up .) , Section
4-4
Data for set up 4, Section 1-1
Data for set up 4, Section
4-4
Data for fletup 5, Section
1-1
Data for set up 5, Section
4-4
Data for set up 6, Section 1-1
Data for set
up
6, Section 4-4
111
113
11 5
117
11 9
1 21
123
125
127
,
•
NOTATION
SYI-'lBOI,S
•
xiii
,DEFINITION
UNITS
("-effic ient
Co-efficient
Maximum SCOur area
PrOjection length of ,grOin,
c
Sediment concentration
ppm
D
Particle diameter
ft
Maximum SCOur depth
ft
Median bed material size
ft
downstream
f
Lacey's silt factor
Downstream length protected by groin
ft
Orthogonal polynomial
Flow rate
q
r
Discharge per, unit wid th
c -efficient of corrp.~ation
S
u
u/s
~I
""'~',
slope
Velocity in X-direction
upstream
ft3/sec.
ft3/sec/ft
,'ft/S~c
Average width of the channel
x
CO-ordinate axis
Y
Zb(Y)
Distance perpendicular to river axis
Bed level
ft
ft
-
-.
,-,
CHAPTER
ONE
INTRODUCTION
1.1
General
From time immemorial, rivers played a very important role
in human civilization. The availability of enough water for
drinking and irrigation, the convenience in travel and trade
throu~h waterwayS and the fertile agricultural land of the
i
flood plains have attracted people to start living near a
I
river considering it as the fundamental heirarcy of their
\ I
>
development. As a result cities, factories and .other important
structures have been built along the river banks.
Besides these blessing of the rh'er, it caused tremendous
hazard to man by occasional flooding of the land ad.iacent to
the river and by severe erosion of its banks during high discharge
and flood. This unchecked erosion causes loss of natural resources,
destruction of engin,,,eringworks and loss of lives. Also, the sediment produced from the bank erosion and bed scour can damage flood
plains, urbaQ areas, navigation facilities, downstream r~servoirs
and other channel improvements. To check these losses man ha
a
attempted to stabilize the river banks.
The problem of river bank erosion in Bangladesh is quite
aggravating. The three maior rivers, tho Ganges, the Brahmaputra
.-
2
and the Meghna, together
distributaries,
the rate
numerous tributaries
carr1 n huge discharge
of these alluvial
continually
with their
riverR,
eroded.
A recent
of migration
about 6880 feet
specially
and sediment.
and
The banks
at the bends, are being
study by Rahman(36)
showed that
of the Ganges-Brahmaputra confluence ia
per y.ear. The study also sho,'led that
of bank erosion is about 1100 feet
the rate
per year.
A huge amount of money are being spent every year to stabilize
the eroding bends. Various methods of bank stabilization
are in
use of which groin is
commonin &'lngladGshbscauRe of its
adV8.n-.
tage. in larger
carryinr; higher
The
protection
rivers
sediMent load (10).
of Kushtia twon from erosion
of Chandpur town from erosion
Sirajganj
of ~1eghnariver,
tOlvnfrom Jamuna river
on Feni. river.
of Gorai river,
and protection
protection
of
of Shovapur brid';e
are some of the examples' Of theext'ensi
groinsirithiscOuntry'
protection
ve use of
,. ,
(5).
,
~ide
the' problem of b~nk erosion
V:~ry'd{iil~ult
;to ;tudyi;n6effec'{of
and
stabiiizationwork.'If
thes~ va~i~ble's -separately
0.t:i..6n
\iI' \h'e"'p:r\)'bl8'mis yot to be
a:ridh~rics'aha:iydcai~bl
'is
0 btainod.
So, small scale laboratory
study may be a good approach to have a
bett8rh'nderst~~di~g
'~roblGin arid
"
,
.;
;"."
oftha
'r
-'
{he
obtc"\iriedresul tsrri~y'
-.
..;
,"'
.',
,
..
. ....r" ... '
. ,;..
[0'
'.
r' ", _,"
..
,
:
-
,"
.
3
Small scale
picture
of the
actual
from deposition
accurlltely
labo:('story
is
whereas occur8nce
more silt
For oxa!'\ple.
channel
due to particle
material
in laboratory
channel
of scour
deposition
is
is
stlAdy
be usefUl
in predicting
resulting
can not be reproduced
suspension
slower
than
movement
from small
th8 prot0typ2
channel,
an attempt
in excessive
obtained
the
(19) . Also,
in natural
Therefore
may resv~t
results
true
which move on or near
quicker.
limitations,
0
sntation
becclUse bed load
goes into
wi th this
02."1
doe s not always f'"i"8
in suspension
in the laboratory
bed and very little
permit
situation.
of materials
in such a channel
silting
study
scour.
scale
bohaviour
to
Even
laboratory
thereby
ellininating serious errors in design.
1.2
Objectiv,)
of the
The present
the
st'1bilization
So.
this
study
day knowledc:e r<:'g2rdinp: the bph2viour
of bends of the alluvial
study has bc,en ta.ken up ,'lith
the
river
is
folJmdn"
of ""Tains in
inadequate.
"''lin obiectives:
CHAPTER
T~!O
REVlEW
2.1
OF I,ITERATURE
Introduction
1m
alluvi"l
prolonged
the
channel
interaction
characteristics
material
of sediment,
adjustment
is
channel
gradient
to the
of the natl1re
rqlated
between tho water
these
0:"
to their
channel.
probably
and channlel stabiliz3.tion
is
iDportant
works.
is madE!on channel
patt'e'rn,
lization
spqc:;'e.l emphasis
work "ith
pattern
stable
which is
factors
hoth river
followinp:
alluvial
mechanism
An understandinil:
and the
for
In the
dischqrge,
An adQitional
channel
patt':erns
by the
of bed and bank
and cross-section.
channel
Occurance
the
status
and sediment
composition
and the geomotry of the
of channel
tied
r~ach,,:s an GquiJibriuin
are
reczulation
a brief
channel,
en groin
that
review
bank stab i-
and scour.
2.2 Channel Pattern
Tho channel
patterns
that
hrwe been recongis8d
ar(~ straight,
"
braided
and ffi8andoring.
and all
channel
c[',t'ogorh,s.
rivers
about
f'orl1':sin the
Perhaps
hav,ieither
Ri:"ers' nre
ten
HowevGr, this
field
a more logical
n singl~
s~ldom straight
chClnnel widths
channel
classific9.tion
are not
covered
clar,sification
or multiplo
through
is
arbitri.Cry
by these
three
',vould' be th2,t'
channels
(38).
aroater
than
a dj,stunce
and so the des:t"n[jt'j:rm of
strgialct
implies
5
irregular,
sinuous
or non-meandering.
Observations
Vanoni and Leliavsky
(28)
neither
bed nor of a straight
of a uniform
imply that
of Gibson,
a strai,&;ht channel
line
is
of maximum
depth.
A braid'?d
channel
is
on8 that
is
divid,')d
into
seV':lral chaMels,
which successiv()ly
meet: and redivido.
The' seperat0
braided
stream
divided
or bars .. The building
central
and lateral
development
will
bars
si tuations
Th,? ratio
and 1.3 to 1.9 in
data
the
of slopes
from meandering
=
where S is
Because the
0.06
the
channel
banks are unstable
and Q is
slope
reach
is
the
In thJ
of the meanderinf? pattern
most comlTIon
onE-', will
o-f'di'TidRd and
to 2.3 in field
'['he equation
and braided
of a
channel
bankfull
discharge.
transport
per unit
,Tidth
low.
on rive1' patterns
of Which 1'ofo,'''nc, .. can be made to standard
15).
,\ brairJ ed channel
as:
of sedimont
A largG number of literatur')
(12,
of
wide and shallow. and the channel
tho ratio
of channGI may be relatively
publications
of
....
Q-.0.44
braided
of a
of th,: process
from 1.4
flume (28).
by Leopold and Wolman (28)
was given
part
channels.
was found to range
which seperates
S
an i.mportant
of' braided
slope.
channels
by islands
is
and shifting
have steeper
undivided
line
are
chann'Jls
follo,Ti.n,,, section
of alluvial
be rdven.
books
streams,
ar0 available
(28,
22) and
a bri pf des0ription
Which is
by far
the
6
2.2.1
Meandering
Chffilnol
A meandering
flowing
channel
cloc!rnise,
stream
patterns
aro usually
of relatively
knovm that
many stream
assoeiatc;d
erodible
cut
into
to observe
streams
investigators
initiation
solid
(14)
are worth
Shahjahan
to mention
primarily
ing and deposition
the
rock or hard
similar
to
that
of
plains
is
strata
bed.
these
Friedkin
from local
by the
In~lis
also
in deep
of rivers
river
This process
the
(16),
"slope
ffi'"andering
o:f bencls along
main.ly control
the
show
mOves d01.mstream. Such
streams
river
overload-
seclimcmts moving
by Fr.i(~dki"nand Inglis
that
of
and Yano(16)
and consequent
a seriGs
tGnd8n~y has been found in many alluvial
along with valley
Kinoshita
Concluded that
as a whol? slowly
Shahjehanconcluclc'd
in alluvial
.investigations
of the heavier
producos
j>westif"ations
b'?tl.;een R'eometrical
bank erosion
The exp(C'riments conducted
Ganges (8).
laboratory
rel'ltionships
(38),
here.
the meander patt0rn
meanc1er.
flood
HowovGr, it
and developmcmt of meanders
and have established.
Freidkin
that
Dl9.torials.
one
These types
with broad
hav8 ccnducted
and flow characteristics.l\.Inont,:s
stream.
wise.
loops,
phlins.
Several
along
anticlock
and 0xhibi t m;;£mderihg pattern
in flood
results
of two consecutive
and the other
consisting
gorges
consists
such as the
cmn. ssdimrmt
discharge
the @:80metry.of str0am
in
7
2.2.2 Theories
of Meandering
Several attempts
condition
under which
and to Gxplain
ism of mGander
of meandering
is initiated
of ffi,,:andor
development.
are able to explain
formation.
groups,
Earth's
a.
the process
the mechanism
of these theories
general
have b:,on mad''?in the past to stipulate
But nons
sp..tisfactorily the m:'chan-
Thes') theorins
may be divided
into six
namoly _
rotation
theory
b. H,?licoid9,1 flow theory
c. 1hd concept of graded
"
d • 'I;'
l',lnlffium
energy
e.
Disturbance
f.
Dynamic
concep t
theory
instability
A very brief description
Earth's
2.2.2.1
Coriolis
stream
Hotation
force, which
of earth to experience
theory
of these theories
Theory
causes an object moving
a tran~verse
causa rivers to have th8 tendency
right billlkon the northern
southern hemisphere.
(aftor38
and 16)
are ~iven belOW:
force normal
to its path,may
to erod" pr'cferentially
hemisphere
th'Jir
and their left bank on the
Howev'3r, it has been shown
,by Quaraishy
that th,~ tonne-ncy of the str'am to defloct
,~ith3r to the right or to the loft is murely
having
over the surface
hardly anything
to do with the earth's
a chanc,? phenomenon,
rotation.
8
Neu (33)
in a stream
has shown that
because
of this
secondary
and the
r(',tio
secondary
of (,arth's
rotation.
circulation
of depth
to the
average
Flow Theory
According
theory,
helicoidal
producl)s
or secondary
secondary
flow.
by ,'SGVGral rosearchers
e.g.,
Einstoin
of the authors
secondary
the
f"i.l
cinsky,
currents'md
result
of
any disturbance
(after
ann Li,
which
l)Griodical
stu0,icd
.Einstein and
39), I,eopold Tanner
any cause for
their
place
of flow.
the
:F'u,jiyoshi (after
to offer
of the
have bSGn ')xt8nsiveJy
Shen, Sh'm and Komura, G,)lrlstein
:Prus-cha
is
intesity
cem 1,';,,0. to mcmndnrin.g. The
currents
38),
velocity
Apparently,
circulation
developed
The relative
m",llldering
phenomena of secondary
(after
is
depends on latitude
2.2.2.2 Helicoidal
to this
circul8tion
16).
the
However,most
ini ti!Jtion
TQvers"l
of the
of si,?"n along
ch'),nnel.
2.2.2.3
The Concept of Graded stream
According
winding
entend
to
this
COurse until
that
the
riVer
concept,
its
the river
b'o'd has bc"en lengthened
would be at
have no reascn
why a river,
SCOur sideways
inste"d
would soek itself
grade.
eVen if
it
of dCiepening its
to sucb. an
But therG appears
is not
at
ch31lnel'.
a
grade,
to
would
9
2.2.2.4
Minimum Energy Concept
It
is
o~ten
supposed
related
to the
theory,
a channel
length
energy
elaborated
j,nterms
The concept
Joglek'lT
ing is
(8).
former
accentuating
energy
According
tri':cs
its
to
to
increase
slope.
This
a random walk theory
They contend
is
th2t
this
its
idea was
or a thermodyna-
load
tho primary
during
SlOpe) by 'lcpositing
in eXCGSSof that
slope
leads
to a decrease
tho width
of the
deviation
flow is
then
bcmk,. leading
the
wa.ke. On the
curvature
other
to
if
the
of meander J:romationwhich
based
on excess
load.
do not
on the
equilibrium.
and this
ban~s are
axial
not
flow is
to
cquse rrore flow
alon,7 thelattpr,
meander in
LeJopold and Wolman reDorted
cases
tonds
one bank th-m the
of flow anCi producini"
hand,
sediment
for
from uniforI')
shoalin"
load
in denth
ch,'nnsl
necesso.ry
A river
sediment
rGquircd
by many
cause of m82lld'3r-
floods.
to c.'luse more flow to"nrds
Additional
towards
stream.
decreasing
of either
On:Lya sli,:;ht
necessary
other.
its
in
to increase
resist.'1nt.
then
thereby
up a stGcper
increase
tends
excess
of sediment
bed when th", load
This
oj' the
of minimum energy has boen questioned
an excess
to build
proce ss of me"Jnr18rin~ is
(38).
mic analogy
like
the
content
havinr;
by meandering
tha.t
fit
in with
tho'
some
theory
10
2.2.2.5
Disturbance
Theory
,1ccording to this
otherl'rise
straight
theory,
the disturb'Clllce causeCi in an
ch8nni?1travels
as to CQuse change in flow pattern
initial
disturbance
Werner (16)
postulated
the straight
alluvinl
one be.nk to trw other
an elnborato
initially
(,rosion and the first
theory,
tho formation
analysis
of meanders is duo
(38)
the variation
as
that me8ndering is an
to be self
";'
exaA"ger".tin.g:.
of streamwise seconcl.8rv 'flow,which
across
vorticity
vector.
the channel,
ents of vorticity
is generated
strOclffidirection.
Obv:j.ously erosion
as it
Because of
a streamwise compon-
is transported
in the down-
occurs when the secondary
flow hl'l's a dowrlwhrdcomponent of Yic]oci ty at the
,",
vector.
due to the bed shear 'lnn hence exists
cross-channel
in velocity
,;"
made
is th"lt meandering is due to the cycle change
of rototion
:l
".,
of m(,anclerina:, .!Orkin/< on the
Q~ick (35) also argues
is generated
only as
from
bend forms.
is merely the strs'lmwise compontm
t of the vorticity
The vorticity
in
Theory
phenom"mon"Thich tends
in the direction
sprial
oscillation
the bed cf the stream could be tre8ted
His main contention
initially
This transverse
by some
oscillation
of the bGd. HanBen .'lnelC8llender
plane.
instability
stnrts transverse
starts
stobility
assumption that
in mesnders. The
me~illdersare initiated
stream.
D,ynamicInstability
According to this
i tsolf
that
in turri,
whieh,
to the instability
resulting
could be caused by v.8rious circumstances.
disturbances
2.2.2.6
downstream in such a way
..
11
boundary
and d,"position
ThE)'lirection
channel
to
of
such reversal
no cirterion
a stream
the
probable
2.2.3
vori toi ty
be the
is
which will
(9)
as
therefore
bonr]s of nen.rly
frequency.
curvature
segments
will
the
of the
has 'classifi
the
with
only available
wher",as,
in
of rJiffercmt
certainty,
r,d moanders
shape
r'l"l.ii'J,n"l
varying
means of predicting
mb'lnd8rs are
str,,'lm
to ilefine
aver'1;:;e mean:Jer characteristics,
or the
tortuosity.
Mcmyfield
anRles.
If
of
and
of
maae up of
the meanders
will
and it
che,nge
may be difficult
c:cmbe doscri bed by me2.nder
of the m'3ander beltM
B
engin,':ers
radius
(Jach bend is
conc1i'erably
of mecerldering str89ills
width
a tr'l.in
J.n anp].i tude
ch'cracteristics
length
l-1 , and the
L
The empiri-
and fr0quE-lncy. Irregular
alonr, the
length
whether
as rA{,:ular and irregular
2.nd melYvary
and componnd, msander
The geometry
is
ChalIDol
compound mo!mders,
of the
these
stream.
smne curvature
deformed in
of meanders,
Simple m8!'m,lers have b,,'ll'] s wi th a single
irregular
related
meander arnot.
simple'J anel compound. Regular
meanders are
changed "lue to upstream
indicnte,
charncteristics
Geometry of Meanc1
ering
and also
is
mechanism of formstion
plan-form
ChitaJ,e
has an upwP,rd component.
of vorticity.
of given
criterion
when it
•. The ,,"!velen;;;th of the meB.neleris
aVGilable
cal
are
streamwise
deflections
whatever
occurs
or by the
and research
sinuosity
workers
hove
12
attempted
to relate
these
averafce char'lcteristics
characteristics.
Relationship
rivers
plains
and flood
2.2.3.1
featur"
bend a helical
It
obtnin
informatj.on
is
navigntion
of meanc1ering rivers
is
importnnt
deterministic
analysis,
and . the other
because
Deterministic
the mobile
shear
at
of the to'
of the
which is
stochastic
of the
NEDECO(1959)gives
forco
the
this
fixed
b=ks
bo zero.
both
the
time
slope
dischQrge,
such that
This implies
thnt
and friction
ai' the b8d
due to gravity.
Considering
due to currant
for
j'".adein the
under a constant
assume a Iaternl
due to current
equ~tion
design
in its
As yet
describe
the
prc:rUctiOi1~
restricted
to
to
Pret1.icti.."lg Bed Level in a Bend
b3.lanced by the: component of force
equation
in order
bank for
approach.
"Jodels :hil
in bed
and width for
in use for
the bed 1iill
force
bed level
of the) simplific,'Jtions
eventually
on a grain
a variation
depth
Appro':lch for
beneTwith
bed will
the resultant
is
ann stochastic
For a circul'lr
the
for
the bend . In each
available
approach
applic8tion
det8rministic
this
Two methods are
practical
force
the
is
and causes
to predict
and (b) thE} levc'l
the
2.2.3.2
produced
on :(1'1)
of bank prot')ction.
is
investi~ators
may be found in many books (28,22,16).
current
level.
the
by the
flow
Meander Bends
A typical
One is
proposed
to the
in a ch'lnnel
pr dicting
bend.
bed level
as
,
\
_ 1_ 1
1
1
(- -)
h
ho - (,.
)0)
where
tho
I
is
the
correction
i is
the
outer
of
for
the
to design,
river
for
The oquation
river
the
with
zoro
examplE), tho requir';d
bend to be cunvex,
since
c<
is
flow in the vertical,
stands
density,
for
D is
the value
at
/11.5.
equation
tennency
(2.2)
of flow
tlw rele.tive
2.2
ono unknown ho'
shows the
nenth
non-uni~orm
9.4Ll.5:'7(
For a given v2.lue of 'Y)
{
across
h is
and subscript
Md also,
...
•••
L\ is
enerp:y line,
diameter
bank.
distance,
coefficient
slope
t'he parti,cle
ran ial
0_''2-
_1_. _5_0<-_1_'
LID
for
doscri be s tho
This
equation
d'Jpth for
can be usod
bank protection.
the lateral
in most cases
depth
bod profile
1.5
<?(
in a
I L1 D)
io'X(')
I.
1•
This
equation
:for practical
i.
The disch'J.rge
the
functi.on
uniform
iii.
.:mn [,(enerf'llly inadequate
becG.us'" of tho follm.i'ing:
is
assume,j to be const"1nt. 'This
berJ slope
is
l'iillchcmr"e
not
as a
of time.
assumes
bed material,
to phase lag
The Clerivation
sub.ject
theooretic'll
case and the
The:: derivation
leads
rather
problems
usually
ii.
is
to
(NEDECO, 1959).
grain
bed. m8.tf:?rial.
sorting
bc]twGGnu(x,r),
takes
h(x,r)
assumes a fixod. bank.
erosion
be extended
uniform
provided
thon
tho
in principlG
If
For non-
place
and this
and D(x,r).
tho banks are
theo derivation
dor;rc;e of orosion
is
known
c,",n
14
The r1.er;ree of validity
by comparison
is
fair
but
it
should
of the
can b6 'l.ewonstrated
be noted
boundary
that
a specific
condition
h '
o
A~reement
dischar~e,expressed
had to be chosen
for
calculation.
2.2.3.3 Stochastic
Approach for
The deterministic
for
design
models.
in this
Stochastic
On (i)
chann'-l
Better
results
(11)
offeree]
He?assumed thqt
give
the
r:eometr.y,and
(iv)
wnl1 efl°8ctS.
cross-section.
Then,
i
leno:th,
f'
and (ii)
~Jall ef-Pects
'ire
betw8en the v~rious corss-sections
consir:1ered
determined
crass-section
series
is
new matched
of orthogonal
perpendicular
by the
to river
axis
upstream
P l"' (.1),
and thus
is
r1Gprcmrtant
'ire
(iii)upstream
simi18r
the
-Par
diffe-
o~ the resch
l;:E~ometr,Y.l~ach me8,su:red
by least-square
ploynomi81s,
required
n,?p:lected,
rence occuring
are
from scale
of bo,l mat"ria.l,
(i)
enot~h
s"ems attractive
beo. toporrraphy
composition
rastrictec1
accurate
a framovmrk that
(ii)
Of
results
be used to mal,," the
rivC'r regime,
For river"
Bed Levol in a Bend
can be obtaineri
mod'"ls cem also
Einstej.n
r'_?spect.
Pr8dicting
model dOGSnot
pUrposes.
pradiction.
all
2.2
of measured and computed cross-section.
as a function
the
of equation
method. ~lith
in ~lhich .1 is
th'3 bed level.
a linear
measured
Zb(Y) is
approa.checl by
Zb(Y)
=
aopo(y)
+ a1P1 (.1)+ ...•.•.••.
+ arPr(y)+
•..•.•
+flNPN(Y)
(2.3)
•
15
Legendre polynomials
are
"'efined
malized
on c', restri,cted
by meQns
describe
the
a
n
suitable
their
cross-section.
are
P upstream
of
in this
intoTV',cl.
the width,
Of'
riyer
crass-section
section
art) very
linked
the
A linear
as they
If ,the y-v'l.1ues fire norshapes
teTe adecl1late to
The pare-meters
Kith
n
respect
clu'vature
for
r
any
C in a cross-
relation
r,n
a
is
8sst@ed:
.e ••
p=1
l'he coefficients
whereas,
a r,n belong
tb3 coeffici",ntR
d"ter,mininl':
the
(2b and 0),
these'
T'o enlarge
Cfor
more rese:::-,rch is
2.3 Stnble
,\ stable
that
method into
the I'Tholo rivor
:from th", exiRtinp
ce,n bs used,
re,'ch.
river
By
w'offietry
tOl::8ther with
th,.
to obtCiin th," coefficionts
no not vary
too much in width.,
by :;;"'oins perp0n,hcul"lr
q p01yerful tool
for
to
riv'.)r
the
river.
enl,;ineering
Channel
to Lane (25)
channel
cross-scction(n),
requir!3d.
Juluviql
:',ccording
to
the new bond,
not pTotected
this
i,'
co')fficients
in new bends in rivors
b,-mks are
L apply
coeffici'3nts
,1psilJJl v'11w;s of
the
to c. particul,"lr
ie
a stc1ble ch,mnel
[',n unlin",d
"arth
chann"l
may bo defined
as;
(a) which carries
16
water,
ably
(b)
the
bank~ ann beds of \fhich ar'" not
by moving water,
a.nd (c)
scourwl
in which ob,lecti0nable
objection-
'1'?Dosits of
-
sediment
do not
occur.
hccor'1ing
si tion
and scour
period
of time thE, banks and
refers
to a chc:mnel c,"rrying
material
do not
in
such a, way that
move. SL~ilarly
'mFi.terial
stable
can t'llte' place
and cnrrying
chnnnel
if
in the
de~inition,
channel,
cl'28r wat'ar through
th() sediment
wat',r
flowing
sediment
This definition
loose
particles
through
mixture
two conditions
minor depo-
but over a long
bed must be stsble.
a channel
the last
to this
alluvial
on the
loose
poriph(,ry
alluvia.l
can be term"d
listo0
etS a
by Lane are
satisfied.
The charact,'ristic
of the'aIignmont
of channel
may ch!mge "rithin
year.
2
deltas
into
over a lonl': period
co,ntly
that
small
as well
shows little)
tts
s2ffie reach
load
the
carrying
may pass
of bed,
but
these
of tbese
stsbili
from ye8.T
slopes
".reo st~nifi-
riversqre
such
carried
source
cnpaci ty and other
types
to
anFradln,2:"der~rading,
from its
v::lrious
to
3.c1vll.ncement
to mouth.
r,mount and sic:e of sedil1".ent enterjng
through
ty
rogime.These
'1ownby them is
may have either
cl1ar;:;,cteristics
118turG dependupo:'l
the
as its
variations
pIe,ce,
Th'c?characteristics
sEn,. The SO,11eriver
river,
take
sen,iMent 10EliJbrou;;ht
other
is
the) sea c:cniichanl";'"s in bRc1.9,nc1,
water
of time~o
(39).
most of the
stClble =d
tion
yeoar but
and slopes
channel
Change" s1.'.chas scourinR; and siltin",
of the
the
s of stabl,'.' alluvial
factors.
dependjng
of Sec1LfJlC)ll
t 102d c:.ndc1isch'~lrge "ri th time.
Its
the
);ven the
on the varia-
But when this
17
equations
the
equ.~clis8R over
anergy
mnterie,l
of thE; str"'JP'
suppli",'!
Factors
of
she"lr
slope,
tion
to
stress
to the
it,
chmmel
'1t bed and bunks,
propertic,s
ch'lnn(]l
along
stream
and ero sion,
the
1'ITherc local
inc;ludes
has been
distribution
'J.isch'3.rl1:e; 1011""itudinttl
the
the
the
seep.~:o;efrom ground
ground
and the
critic,,,}
found
composi-
tractive
force.
to be' helpful
in
of a rivGr
ji[cthods
banks
stnbili
b"como 1ve8.kand susC'."ptibLe
ty
oftthe
f.1..Jw
.. c:ondt tions
bed in such casps
includes
all
the
the
river
and. rlv8r
en:e;ineering
S(:j,'Jip".8nts.
purposes
incref~serl
dn.e to
for
erosion
drai.na.rz:e from irrigated
work (30).
rrJaches
sh::-,0.r str0sS
and to
effective
Stabili?:8.tion
(7) .. Uso,
in
.:-l-t
Stpbilization
works c;onstruct'Jri
Tlow of chllnnel
her] con+'iR:Ur8tion
:for naviwltion
f101\T
caus.::~ ::In incren.gr.:' in
the
to c<.oving
bCJdrrny be:mdang,.'rr,d
th8 b.~rJ and b~,nk must be stabiJizc~d.
to ,,'.lid,? and confinf?
stabilization
the
stable.
.;-racbtion,
influences
avera",e
bank stability.
1'lhen the
of flooc1s
is
on the
to transport
bank full
and its
ch:onnel b,.nk
so th8.t
sufficL:mt
or from chr,m:wl to
2.4 B:!nk StabiL.z'1tion
re'-u1ate
just
th,,', stre'lm
of bed m!1teriAl which
Vegetation
riv8r
is
of time
governinoo; chA.nnel st".aiJ. ity
sediment
watc'r
a period
on a
contr01
and s?fe
and
movement
wor~:--ar.? [-).1so reouirpd
on account
OT the
l;J.nd r!iay req~.J.ire
18
JiivGr stp.bilizRtion
prot",ctive
J'lE\ybe done by dif'fer~Ilt
:l.,ovices which
bo classified
ffit''Y
of ';Ihich thfW arC) constructen,
or accordin,7
methods
to th?ir
but
short'-run
2.4.1
or applicntion
CD.nbe fOu.nr1.in many reports
purpose
also
staoi]
on the
effect
iz.ation
. Details
n.,?vicC's
Of' these
(10,8,42).
The suit.gbi1ity
is
not
dependent
fund .ccvailable,
and ease
as to the' materiRls
the gC:'Ileral shape Of' thn
functions
of the) method use.:l for
tYPGS Of'
conv(mience
only
on the
in use
for
of' maintenance.
Groin
1l groin
is
a continuous
bank or barric,r
and is
placc;d
or deflectiw,
width, (c)
and (d)
Groins
transverse
found,]'} on ground
from a be.nk into
the
tho
promoting
trapping
sediment
function
It
serves
(b)
served
as follows:
or .man-made
motion
fillY time
purposelJ
of
(n)
normal
of water,
running
guidinc
ch::innel
of se,'.i!lk'nt where
up new river
desired
banks.
to the; m.othc.d 8.nrl rn8.terials
by them and their
accori!iYJ'" to the
to the' J1Jethod and [,,'iterial
can be classified
primary
este.blishing
101,d to build
accoding
natur,-ll
flow at
the
and doposi tion
2.4< 2 Glassific3.tioll
of Grojns
of constr1.18tion
f;ccording
to the
by the
of flow,
scour
may bo clccssifio'1
construction,
wetted
flow.
axis
'2lrosion resist:Jnt
0-<"
of
hed ..,-hts.
method C).Dd
materjal
constructi.on,
;:,rains
19
i.
Imperm'?oble groins
(a)
SinRle line
01'
steel
or concret'e
sheet
pilinf'".
(b)
Double line
07'
steel
or concrete
sheet
pilinc;,the
space bein~,' fillwIup
(c)
Rock dike-plain
l,,:l;th vc:rious
cement' concrete.
types
of materials.
('ro~lted or asph~1lt
surf,s,ce
ii. Permeable
(a)
groin
Prec2st
plain
cement
(b) Precast
pluin
cement concretlO cells
( c) jVjetr'l rec tcngular
(d) Pile
(e)
armoured with
groin
resistance
consists
of" rock fill
m?terial
like
c'c'ment c()ncret~, bloc!{s.
and does not
stre"m
is
It
"llo'-T appr;,ci'Jble
thus
defl8ctc,d
Such cUI"'nture
t01Vards this
'now through
is' conducive
slipping
scour
in the
hole
the
~routed
of the
pr?cast
obstructions
th0m. The stream
down stre"m
01'
hank from l"hich
to the mov',"l(mt
siltin,~t'lko:J
of stone
or (:~arth care
as a solid
and immediptely
b1nk rtnd h8nce
To prevent
stone
acts
have conCf'.ve C1)I"'T8tilr8 tm"ords
extends,
the
cell
Tree groin
Imp~rm~nb.l-,-;groln
current
block
groin
i. Impermeable
plain
foncrete
01'
it
the
j,t
bed load
Dlace there.
{:crain nose and shank into
immediate v5cini i;y, an apron
is
usually
20
provided.
This
lauching
to
apron
shj.eld
the bottom of the
A.very
flat
expensive.
should
the
slopinr,
faces
slope
faces
dm'rn to
slope
'['herefore
for
ii.
Porms8ble
".re givon
deposited
perme:'ble
R;roins are
III
in damping the
sedimentation
used in
its
bank lin,?
marc ef:"ectiyr,
strenc.th
the
groins
Materials
of1:2
to
E1ction
inaic2tes
sllspendedinto
buiJ.din.C'"up.
in str'33.m that
rivers.
this
prevent
dur2ble
Therefore,
transport
action
heavy
results
ben!: erosion.
becomes more or less
do not require
As
parm'1rtent
materi,3J. to
be
construction.
the
are
cheaper
and therefore,
this
for
river
works where'stone
is
1-Then constructod
<10(;'09
Occur
obviously
or rep811ing
starts
p.nd thus
bank line
'I'he rnatel'i,,J ..s used for
groins
of flO1,v.
cor1lY)."lratively clear
occurs,
permeable
is
pcrrrwabili ty of a ntructur8
and the
erosive
and the
bed level.
norm8,lly :.\ slope
from tho doflGctinp:
on the velocity
vrater&:et
load.
the deepest
from h",I,d to bank.
of an impermsablG structure,
sediment
bank from below
groin
j\S distinguif!hed
a dr:J:npingaction
of the land
after
CAn bo rGduc eO. from head to b'illk .bocauso
ct iminish,';s
graduCllly
length
the nose of the groin
groins
1: 3. Scour protection
scour
be of sufficient
in
construction
typ"
th(~' C.'lBe of
of groin
dif"icult
dOdB not
of permeaule
is
groins
spcccinl1y
ad,?pta"ble
to obt",,:ill. Permeahle
crcat(--: lJny abrllpt
imp~:'r.me~.ble groin
change that
[-~.ndsn, no ssrious
21
eddies and scour holes result. T1].isis perhaps the reason why
silt deposit is evenly and quiclky affected"
Permeable gorins are not strong enough to resist shocks and
pressure from debris, floating logs etc. Therefore they'are not
sUitable for upper roache's of the river,
i. Attract~ng
type of groin
The groins pointinpo in the downstream direction of flow
causing scour holes tc form closer to the bank than the groin
inclined at right angles are generally called attracting type
of groins. They maintain the deep currents close to the bank.
The main attack of the rivers on the upstream face of the groin
and therefore r":quires better upstream protection compared to
that on the downstream
(Fig.2.1).
This type of groins are not generally recommended because
they endanger tho adjacent river banks causing failure of protecting certain structures from bank erosion.
22
ii.
Repelling type of groin
Groins pointing upstream against the flow causing the flow
to deflect away from the bank is generally called repelling
groins. This has the advantage that during the flood. the overflow
is directed towards the centre of tho river thus avoiding strong
currents over the flood ple.ins and near the flnod diks.A
groin
pointing upstream produces a more desirable curvature to the flow
dOl~stream leading to pronnuncod deposition. Rlrthermorc, such a
groin has a larger stagnation region on tho upstrpam sirle;thereforo it is able to project a graater length of bank than a groin
pointing downstream (16). Franco I s finding also ..
support this
view (13).
The an,gle of de"'lectionupfltreom varies 600 to 800 with the
banks or in OTher words, the groin facinpups+'ream make an angle
0
0
of 10 to 30
with a line nerpendicular to the b"lnk or thalweg.
Due to the disturbance caused by the hea.d of the r'''pellinggroin,
heavy seoul'occurs downstream. Therefore,. these groins should
have a strong head to resist the direct attack of the swirling
current. As in the attracting ,Q;roinscour diminishes from the head
towards tho bank and protection of the slope and apron can be
reduced accordingly.
Recently, literal use of the metaphoric colloquial terms
"rt,pelling 8.I1d"attracting" applied to groin !'lction,h.qflcaused
misunderat8.l1ding.Tho origL~ator of tho torms eXPlains( 6):
23
"The typo of groin
repolling
three
groin
at poona,
tYP8S, namely,
thE\t the water
clescribod
the
should
whero groins
fender
river
Groins
or attracted
and not merely because
pr"vi,:'\• cd the position
efficiently
groin
if
shoulc~ face
Actually,
the natural
impression
iii.
than
towards
sli~htly
of which was
the attracting
groin,
and tho repelling
relative
a rf'pelling
upstream
groin.
of their
position
to river
flow;
but
f':roin worked more
whilst
an attractin~
s"me 45 ne<'2:reosc10wnstream.
rIo not
repel
or attract.
they
01' m°'lnr1erin,ccin a way that
inter1'ere
may give
with
the
or attraction.
typo of groin
A neflecting
groin
Only deflects
a repelling
groin
ann is
the flow.
generally
It
is
constructed
much shorter
in, river
per-
bank (Fig.2.1).
Classificntion
high water
according
These are mainly
type
it;
because
of the angle
pointed
of repulsion
non-submerged
it;
largoly
s correct,
progression
to the
the idea
into
-
WI':
groins
Deflecting
pendiculc:r
2.4.4
it
groin,
'-
the
a
were differentiated
flow smo'lthly past
which attracted
repelled
in the paper was callod
to the height
of groin
submerged or non-submerged
of groin
is
pr::ferrod.
type.
below
Generally,
24
I
2.4.5
Special type", of groins
Besides
the groins described
in the previous
sections,
several other special typOS of r;roins are in use. They are named
after their shepe, local Use or persons
include hOCkey groin, Denehy's
etc.
Denchy's
Okla headwork
T-headed
contributed
T-headed groin, L-shaped
groin was first constructed
The front perpendicular
head is paro.llel.to the current.
Usually,
these are usually
it is
arm of the
the i10wnstream siCle of
the head has a longer arm. f shorter len~h
protect more area from erosion
groin
by Denehy at
on the Yamuna river (India) and therefore
also known as Dei-why's groin.
Therefore
for it. These
of these groins
can
compared to the other types.
economical.
has been used in the protection
Dep.chy's T-headed groin
of Kushtio town from the erosion
of Gorai river and has been proved effective.
A groin with a curved head is known as hockey groin. It
increases
the tendency
of attracting
fore, is not likely to be helpful
L-headed groins with lower portion
flow towrJrds it and,there_
for bank protection.
parallel
to the flow on the
downstream side are also in use and have been reported
effectivo (16).
.-'-
The
to be
~
•
25
2.4.6 Functional
design of ~roin
At first sight the function
might appe~r
of a groin anc.lhence design,
to be straightforwardiri~that
provirle some form of obstruction.
and intricacies
However,
As the material
of the structure,
No gener~l
However,
physical
of construction
a good number
of attempts
amnng the pertinent
from three main fields of study:
model analysis
,1wide variety
Groin length,
height,
can be varied.
construction
there appears
functional
have been made to establish
factors of design.
literature
(a) Mathematical
orientation
of different
"
referred
Heco[Qm,,'llda-
have ori('inated
analysis
(b)
cow1ition.
sha;:e and permeability
materials
may be used for
affect grein performance.
to in the papers when taken as a
to be no crmsensus
design of groin.
design.
for the dosign of groin.
and these can also sometimes
Groin characteristics
whole,
in the functional
designs have been uS8'1 in parctice.
spacing,
A number
ancJ,permea-
(c) Field data unr1er Drototype
of groin
of its
influences the performance
~t is also considered
tions for groin desip"n in the t8chnicol
Physical
regime.
sh8pe, angle of inclination
rule has yet been formulated
relatinnships
due to thoir place-
design of the groin is the determination
length, height , spacing,
bility.
tho design diffi'culties
should not be underestimated
ment in a very complex and sensitive
Functional
they are intenc.ledto
of opinion as te the
26
tJ.thoughthere are many papers
made to prototype
in which
p:roins, there are rcj1ntivel.v a few whidh:
provir1e su+'ficiently detailed
of groin performance.
data for an analysis
Some authors
drawn from many years of experience,
details
of the groin-systems
This is valuable
write their
to bema'1e
own conclusions
but without
giving any
with which they have been involved.
but does not permit other research
make use of their data. For more details,
to the works of Ahmed (1,2) l~ikusa
Nagai and Kubo
some ref'erence is
(32), Monohar
roferonce
and Kikkawa(3)
(29), Tomlinson
workers
to
can be made
Nagai(31),
(4) and reports
of
BWDB(4) and IDFCRC(21).
A lRrge number
repolling
groin
Mathur(44).
Q
w
1-There,
b
w
of river training
constructed
They suggest8n
incorporating
in India was analysed
...
=
length
by Varshney
and
a ,c:eneral equntion as follows:
of groin
(2.5)
.'
= width of active r~ver
.
=
flow Froude number
=
arc-chord
ratio of worst
2.5 Scour
loop
•
1tlhenalluvial
strUctures
measures
streams
like groins
are partialJ.y obstructed
bridge piors. abutments,
the bGd level in the viCinity
of tho structure
by hydraulic
6~ide banks
etc.,
is lower'-d as a
'I'
I
i
27
,I
'I
',I
resul t of interaction
loose
between
bed w.d consequent
a local
depth
drop in the
is
great
the high
I
veloe i ty flm," anc1 the
.,
morl:li
f'ic8tion
"
I
bed]
eveil is
in the
f'1nw pgti;ern.
known as scour.
enough to unc~ver
the
supporting
If
the
soil
Such
scour
of these
I
it may subside
structures,
the
there
and ultimately
.1
washed out
by
current.
Different
methods
of computation
of
scour
h8.vC berm proposoil
II
by varicJUs investigators.
motion
scour
and clear
(whore supply
water
upstream
Di'stinction
is
scour
and Laursen
lowpst
true
if
to account
by applying
greater
coarse
layer
layer
uncovered.
smaller
armouring
for
the
the
of
sediment
is
supply
assumed1
from
can be made to Komura (23)
If
scour
effect
removed during
may deve10p,
embankments(17).
the
is
pre,sent
at
rlepth would be expectei1.
interferes.
form"tion
material
b8d m.'Jterial
bed rock
Komura (24)
rlown to
some ilepth
Tho same
has attempted
of an armour"d. }8,yer during
method of Gessler
or cohesive
sCOur hole
from upstream
assu.m8 alluvial
th&'1 ex):!ected 1IThenthe
is
made betwoen general
(26,27).
e. considerably
is
absence
Reference
The mRtiloc1s proposed
the
ol~ sediment
(where
assumed).
is
(37).
river
t
overlying
scour
endangering
The scour
bed consists
finer
process,
the
sand.
ma.ybe much
of a layer
If
of
the upper
an unexpectedly
stabi1ity
scouring
of piers
large
and
28
Local scour around piers and abutments
so-called
horse-shoe
dimensional
vortex
seperation
system characteri"er1 by a three
of the viscous
system is caused by the secondary
present
'is caused by the
sub-layer.
This vortex
flow and vorticity
in the flow. It has not been possible
already
to determine
pro
the
depth of local scour around the nose of a pier from a theoretical
analysis
of the water movement
investigators
problems
Gill
around the pier. However,
have been able to provide
by carrying
out experiments.
some insight
Reference
many
into these
can be made to
(18), Shen (39) cmd Inglis (37). The following
remarks
should be made about local scour around piers:
(a) It should be realized
thpt the formulae
and r1esign graphs
can at the bpst only yield rough estimate
of the SCOllF
depths to be oxpected.
(b) Local scour around piers in cohesive
bed material
(c)
shows different
In debris-la,:1.enstreams.
considerably
(d)
The methods
the .actual loc".l scour may be
determine
by data from literature.
the mean .scour that will
occur during an extenc1.ed.flood. When general
motion
sediment
occurs and bed forms travel along the river bed,the
maximum
scour depth will be longer than mean one. Neil advises
that one-half
of the height of the dunes be added to the
mean scour depth, however,
water
-
pattern.
larger than determined
proposed
and non-cohesive
scour depth.
the sum shoUld not excoed clear
.. ''''
2.5.1
29
Scour at the toe of aroin
From the model test of ."roins at the G2ngps near Har(1'in.gs
Bridge,
Inglis concl uder1 thot (,roin pro ,jecting "rom the b~nk
into the channel "ive widely v~rying
ranc;ing from 1.7 to 3.8 Dr"
depths.
DL = 0.473
(Q/1 .76 dO. 5)
m
v'clue of maximum
scour
wher~,
...
(2.6)
.f:;'~
Q
discharge
on the length,
groin in relation
In an attempt
varLJUs
discharge
in a laboratory
form:
d
in cfs
d = m.:;dianparticle size
m
in mm.
upon the severity of the river
curvature
depending
depends
=
= Kg'
and position
to calculate
the probable
intensities,
11hmed(2) canQucted
scour depth for
Ht' suggeste(i an equation
. ...
....
where, K is a factor whose value depends
sevor9l
. ..
(2,7)
on the position
per unit width at the groin
constiction.
the SCour problem
Lfter anaJysing
non-dimensional
terms th'lt affect
sturlies
of the following
groin and q is the disch~rge
different
in turn
of tho
to the attack.
channel.
4-
s
angle of projection
which
of
by plotting
it, he "Ief'inedthe
_<-
term ds/q3 as scour constant.
accepted
This constant has been widely
in the study of scour at the toe of groin.
30
Applying
correction
for veloci ;;Y. Khosla
SCour depth with discharge
flow formula
intensity
using Kennedy's
(2). He gave tho relation
,
ds
=
0.90
where f is a function
2
,(q If)
regime
...
...
(2.8)
of silt size and is known as I,acey's silt
channel.
:factors in calculation
tho
in tho followino: :form:
:factor and q is the dischar&'"e per unit width
holds :for regime
connected
He also recommended
in c:fs. This formula
multiplication
o:f ds for di:fferent types of bends.
\
THREE
CHAPTER
Lf,BORATORY
SET UP liND ME/\SURE~mNTS
3.1 Introduction
The Hydraulics
and River Engineering
Department
of Water Resources
University
of Engineering
required
facilities
Engineering
device,
for the study. The existing
alluvial
in this study. The levelling
facilities
of Bangladesh
provided
and automatic
of Civil Engineering
of the
and Technology, Dhaka,
sand bed flume together with the water
measuring
Laboratory
supply system,
dry sand feerler were used
instruments
Were used.
A
and the experimental
from the De~~rtment
brief description
procedure
of the.
is given below:
3.2 The .~lluvial Semd Bed Flume
The 8Rnd bed flume was 50 feet long, 15 ft wide anil abnut
3 feet 6 inches deep having nouble walls alon,g its lenC'-th
(Fi2;.3.1). The two ar1iacent
space of 6" wide.
diameter
The inner .rall
hole with a spacing
and vertical
direction
walls and vicl) versa.
~TSS
by an 'lnnular
proviCleCl.ri th
movement
SDace between
The water
to the desirable
seperated
+
inch
o:f one foot both in hori?'ontal
to facilitate
the sand bed to the annular
maintained
walls. were
of water
:from
the two adjacent
table was controlled
and
level in the sand bed by regulating.
the water level in the annuls.r space. 'ro avoid losses due to
32
seepage,
the outer wall and the bed of the flume was made
water tight,
•
3.2.1
water Supply System
A centrifugal
pump installed
near tho tail water tank of
the flume was used to supply water to the test channels.
was allowed
to enter the inlet ef the channel
pipe line from the pump, which after flowing
entered into the tailwater
supply through
through the channel
by means
to have a continuous
the test channel.
The loss linG attach('d to the delivery
to maintain
through a delivery
tank. It was recirculat8d
of the pump and the process was followed
water
the desire''!dtschariN.
pipe line was used
Requirer1 am0unt of water was
I
allowed
into the test channel
tailwater
3.2.2
and excess was diverten
into the
tank throu~h the loss line.
Flow Measuring
An one-inch
Device
automatic
l
flow meter connected
pipe line was used to measure
tho yolume
the line. This meter was provided
to the delivery
of water flowing through
~ith the facility
of taking
I
th8 volume
readings with an accuracy,
gallon. The time required
recorded
to flow
.10
of one-hundredth
gallons
by a stop watch and the discharge
of a
of water was
rat\? was calculated.
33
3.2.3 The Tailwater Tank
The tailwater
ta~k at the downstream
used as the source of supply of water
was !'ladeto recirculate,
settling
carried
constant
supply line of the laboratory.
water tank was kept submerged
with beffles
from upstream.
by supplying
water
Approximately
the test channel at the downstream
ment permitted
for the pump. As the water
this tank was provided
down the sediment
level was maintained
end- of the flume was
The tailwater
from the main
one foot length
end, measured
throughout
and to eliminate
part of the test channel.
under a constant
This
the test. This arrange-
back water
also helped
head thereby maintaining
of
from the tail-
the stream to change its longitudinal
slope naturally,
for
water
surface
effect in tho lower
the pump to operate
a const2~t
discharge.
3. 2.4 The Sand Bed
A mi ture of fine and coarse
bank material
of the t8St channeL
sand is shown in Fi,""
, 3.2.
of the material
sand was used 'l.Sthe bed and
The graClation curve of the
The mpdie.n size (Cle""inedas 50 percent
is finer than the given size and denoted by d
)
50
was found to be about
which expresses
matcrial,
defined
0.147 mm. The gradation
the size distribution
coefficient
6 ,
of the bank and bed
was found to be 2.65. The gradation
coefficient
is
as:
(3.1 )
where,
d84 and d16 are the size of the bed or bank material
for
34
•
w'hich 84 percent. and 16 percent
finer.
Hence.,f}
materialsre.spectively
are
is .the averac>:e slope of the two s8'c'"rnents
6f
the n:radation curve.
3.2.5 Flow Entrance
An initial
the initial
uniform
bend of about 300 with the longitudinal
channel was provided
meander
pattern.
axis of
in all test sets to develop
This also allowod
a slow transition
velocity
from the ontrance
to the channels.
of about
four foet long was used for providing
in
Thin steel plates
this initial
bend.
3.2.6
The Dry Sand Feeder
.An automatic
dry sand feocler located
of the flume was used
for sediment
at the upstr,am
feeding.
The fee-'!orwas
driven by a motor havinl'"a goar box wi th centr01
regulatin": the sec1:Lmentfeed into theehannel.
curve for the rate of sediment
end
c1Gvices elf
A calj.brati.on
(Fjy.3. 3).
fee"! was prepared
This curve was used to m"lintain the (1,esirer;sW'iment
1 '''1.,'1
in
the channel •.
~~terial
same as that used
bed of the flume was introduced
for the preparation
at the entrance
of the
of the test
channel. from the dry sand fGe,]er. The rate of ser]iment feod
was taken as 880 ppm and was kept
constant
throughout
the test
,
.'
•
35
•
runs. This rate w,<"sdet'''rminG<1by a few trial runs and was
compared
(43);
with the actual
values
for some rivers
this rate was
:founr1
to be in agreement
IUSO
sediment
concentration
versus
Fronde
number
of Bangladesh
with
the
rlot by Wilis et al
(45).
3.2.7 Initial
Channel
The size of the initial
inches
channel
channel was 8 inches wide and 2
deep. This size was kept constant
was moulded
in the flume bed by trowell
as shown in Fig. 3.1. The initial
by regime
Nishat
Lacey's
equations
(34). These
regime
was provided
throughout
using
channel
the values
dimensions
were
and template
dimensions
of constants
subsequently
were fixed
estimated
checked
by
by
equation(40).
3.2.8 Discharge
A constant
in all the test. The
and Slope
discharge
of 0.03222
in all the t~sts.
cfs and a slope of 0.00333
These values
were kept
constant
the study.
3.2.9 Measurement
A movable bridge with a point gauge mounted
for takinr; readinE;. 'rhe brid/7,ewas marked
with zero at the centre that coincides
on it was used
in feet and inches
with the centre
the initial
channel.
The bridge was operated
rail placed
on the top of the side wall.
manually
line of
over a
The rail was graduated
36
in feet and the position of the bridge was read from this
graduation.
To avoid any error due to sage of the movable
bridge, all the readings were taken with the help of a lavel
with a fixed benchmark.
3.3 Experimental
Proc~~ure
For all of the test runs, the experimental
procedure
were
as follow s: ,
The sand in the flume was levolled
anr! compacted.
was excavated along the longitu(linal centre-line
with the help of a trowel and template.
Pi channel
of the flume
To provide
the initial
channel with the pre~c1eterminod slope a string was held ti~htly
along the centre lino of the flume and elevations
at intervals.
were taken
J\fter the channel was excava+'ed. the tailwater
tank and the annular space, between the two walls were filled
with water upto a level on a piece of wood in the tailwater
This level was predetermined
from previous
channel was given sufficient
time (about 12 hours)
groundwater
tailwater
box.
trial runs. The
so that the
level could be raised to t~e level of water in the
box.
Water was supplied to the channel by operating
ting centrifugal
pump. The discharge
the recircula-
of the pump was maintained
at a constant desired. value with the help of the loss line
attached
to the rlelivery pipe. Dry sediment was fed at the entrance
37
of the channel by the previously
rate of the sediment
c'ilibrat,,,dsani fee'ler. The
feed was kept at a predetermined
the help of the ~ear-box
indicatoor.
The rate of change of bank
formation was very high at the beginning
several
v?lue with
of the test run. After
hours of running the channel was found to have obtained
a stable shape. This was evident
of the meanders.
To test the stability
surface and bed elevations
taken and plotted
W!)S
of the channel, water
at four different
in a graph paper.
and bed slope were
the channel
from more or less stable shape
locations
The water surface
were
slope
calculaten.. If these two slopes were equal,
taken to be stable.
Otherwis("
the test run was
containupn. until the."e slope were equal. The time r','quiren.
to
achieve this conr1itinn varied
on whether
from 72 to 125 hours depeni1.ing
the channel was run continuously
or intermittently.
After the test run achiever'!this quC\si-equilibrium
following
status, the
data were collected:
i. Location
of the left and ri~ht banks alon~ its profile.
,
ii. Lccatirln and slope along the thalweg.
iii. Location
of pools and crossings
iv. Cross-section
of the channel at bends where groins were
to be placed.
v. Cross-section
of the chcmnel at upstream
crossings
of
the bends where groins were to be placed.
vi. Cross-section
of the channel at downstream
the bends where groins were to bo placed.
crossings
of
."
38
Also, to observe the ~ovelonment
of mean~ers,
loc~tion
of the banks and the thalweG were taken at ~iTferent
of time after the starting
data
interval
of the t3st run.
Impo,:,meablegroins made of solicl mGtal plates were placed at
the desired locations
was then continued
after collecting
until stability
the above
was restored.
surface slope and bed slope were determined
at four different
locations
data. Test run
l~ain, the water
by taking
to check the stability.
elevatrons
At the end
of this stage the folJ,owing data were collected:
i. Loc"o,tionof left and righ t bank akn!; its profile
ii. Location
and slope of the thalweg
iii. Crass-section
of the channel
at bon's where p;roins
.Tere placed and at corssings where
earlier measurements
I
were taken.
iv. Depth of scour hole formed at the toe of the groin at
+
inch interval
alon9 lines paralle and perpendicular
to the ["rain
v. Area of the scour hole
vi. Length of the area protected
channel, both at upstre~~
placed at the aforesaid
along the bank line of the
and downstream
bends.
from the Groins
39
Sin~le groins
different
of c1iffet.ent projection
loc~tions
anc1 placec1 at
were stMc1ied. A total of six test runs
were made in the labor:Jtory,. In three of them, ef'fect of sinr-:le
groins placed at the 'cent.reiof the ben'1S were studied.
other three, single groins placed at a distance
-
of the average
studied.
In
In the
of 10 percent
[,
channel width upstream
from benc1 centre were
all the runs, ~roins were placed at two different
bends spacing between
at the downstream
them was such that the flow characteristics
groins were not affected
I
Thus six sets of results wero obtained
by the upstream
groin.
in the stuc1y of single
groin placed at the centre of bend and another
study of single groin placed 10 percent upstream
six sets in the
of the bend
centre ..
In the study, groin projections
percent
increase
to
30. percent
ratios were varied
from 5
of tho "vera,ge channol width with an
;,
of about 5 percent.
"
..
CHAPTERFOUR
RESULTSANDDISCUSSION .
4.1
Introduction
To study
groin,
,lata
analysG(1.
the
effect
collecterl
of 10c3.tion
from the
anr'I projection
laborgt'Jry
The nownstrea.m length
set
protectei
of a single
up hav" been
by groin,
I,r'!'the
'.<
maximum scour
the
groin,
width
r'!",pth d
s
the
lenrrth
affecti'"p;
scour
to
at
a more useful
charge
per unit
vo.ria ble.
widely
Because
Also the
the
The depth
of
groin
constant
study
been used
scour
and also
in
is very
compnred vii th those
Ch::lpter-2.
the
toe
of.
b and avera~echannel
sup;gestec1. that
than
b and the
constriction
q is
c1.is-
an importcmt
K 'as us.ed by J\hmedhas been
at
of his
in the
of
in the
the
toe
of the
sugg estions,
groin.
these
analysis.
import~nt
obt,'1.in8f'. fr0m
paraMeters
Lhmed (2)
of scour
the .pr8,liction
sC'Jur rlepth as me8sure,l
s
variable
of the? wL1e acceptibility
have also
formed at
non-r'!,imensional
independant
scour
L
Tor analysis.
of rrroin,
wiclth at,lthe
acceptec1. for
parameters
of groin
toe
area
projection
establish
the
b/W is
in
of groin
W. have been considered
In an attempt
So the
and scour
factor
the groin
oxperiment
.iiffGr.'mt
in
the
design
performance.
has been
f0rmulao
presented
41
Attempt has been made to relate the parameters
analysis
using the computer
of BUET Computer
by statistical
Centre. The relation-
ships obttlined have bGen compared with those given by Hossain
(20) •
.ThG effect of location
from the laboratory
and projection
of groins as observed
test runs .'lrertoscribed in the following_
sections:
4.2 Effect
of groin on downstream
length protection
It was found thn t depcsi tion of sediment
downstream
from the groin a_long the downstream
cause for the siltation
obstruction
at the downstream
of velocity
has been mentioned
in the vicinity
of the area. It
(at the bend centre and at ten percent
of bend centre) and their projections
Figs. 4.1 to 4.12 show the location
the position
after the placements
the do.rnstream lpngth
following
to the main flow
earlier that groins .rere pI-aced at two
locations
and. identify
b'wk. The major
of the groins was the
created by the groin projection
with a reduction
upstream
':Itthe
face of the ('rains. The len/?-thof this deposition
was measured
different
occurs
and proje0tion
of bankllnes
of P,r0in. Results
Dnd thalweg
obtained
protectec1 are thorefore
two sub-sections:
were varied.
of the groins
b8fore and
in relation
to
r1iscussec1in the
•
4.2.1 Effect of projection
protection
It is interesting
42
of groin on downstream
length
to note that as the projection
groin is increased., the clownstrGam length protected
upto certain value
the downstream
length protected
groin projection.
of projection
of projection
increases
ratio, but beyond this value
decreases
with the increase
of
This is evident from figure 4.37. The value
ratio
become'S maximum
ratio of,
at which downstream
length protection
is found from figure 4.37 to be 17% for groins
placed at bend centre and 23% for aroins placed at ten percent
upstre~
of bend centre.
\"rhena .voin is placed at a bend it deflects
the thalweg'
away from the bffilk(Fip;. 4.1 to 4.12). As the i7roin prc,iectfon
increases,
the shifting
starts from a greater
increasing
of the thalweg
distance upstream
the projection,
the thalweg
the flow hits the downstream
the downstream
nation
As we go on
may take such a form that
decreasing
This may be the possible
do not agree with those obtained
This disagreement
in his study Hossain
position
expla~
results.
The results obtained
Hossain(20),
of groin.
bank and erodes it threby
length protected.
of the obtained
from its previous
may arise because of the fact t~at
ignore'1 the effect of groin loc2tion
c1('wnstrG.'lm
length protected.
Instead ('f analaysing
for <'Iifferentproj0ctions
at a fixer1,position
fer different
at different
projections
•. 1
by
on the
data obtained
he analysed
aroin locations .
n.ata
43
From the plotting
and Flood
Control
Research
may be observed
that
less
is
parameters
study.
material
to
parameter
at
establish
vari'Jtion
bend centre
and four
The coefficients
respectively.
where a
obtained
t8ken
for
for
dimension-
in the
was of the
zrins
Th~, P0:;Jsible
bank anTI bed
the
grac1etion.
between
nr0.iection,
correlation
the
the
dimension-
voriable
tion
upto
or'1.er five
seventh
for
'Sroins
of bend centre.
was found to be 0.984,
groin
and
was obtainec1 when
10% upstream
single
prosent
placed
at
and 0.972
the
centre
'"
(4.1)
as follows:
'= 5.26814
x 10-2
~1 '= 3.45609
x 10-2
8. '= 1.29468
2
x 10-3
0
may be that
a relationship
fit
of correlation
1'he equation
bend is
obtained
A polynomiEll varis
The best
polynomi'll
of the
between these
b/W has been chosen as in'"epenrJent
was assumed.
CZ1') {t
maximum Ld/W differs.
and groin
variable.
Drafn~%c
RCP/2b/4 of
stUdy was of different
pr()tectorl
Ld/W as dependant
the
relationships
dis-agreement
used in thQt
downstream length
(Fig.
in agrc3ement wi th that
to this
In an attempt
order
the
Council
PJ.t the v'1.lue of b/1r! for
explanation
less
of Ld/W and b/W of Irrigation,
I
,"
,!
II
I,
!:
44
and
a
3
=
-3.11638
a
4
=
1.33688
a
5
=
-1 .82269
Though equ8tion
4.1
x 10-4
x 10-5
x 10-7
is
not recommended to be conclusive,
shows tho prob.'1ble trend
of !;roin
projection
of groin
on the
thRt the
groin
it
in protecting
downstream length.
4.2.2
Effect of location
protected.
It
has been obsorve'd
upstream
of ben([ contre
. to the
lenp;th
section
.L2.1.
,~.
shorter
than
similar
behnvi"ur
I
Fif'.
of the
when placed
c1o;Tllstreamb8nk protection
of
For same projecticn
upstream
shows the
downstroam length
4.37
rel:,tionship
I;
rntio,
cfmtre
the
shows the
the
as
"I
ten
in relation
escri bed in
of 1,,,,/1'1with
PToin placed
protected
at
ten
percent
with
"roin
rlacen
at
''C\
the
len"th
bend
centre.
The relation
between
Ld/W and b/l'1 has been found to be as
foilows:
Ld/w
=
where' , '1
=
0
a1= 7.92330
x 10-3
a2= 9.58688
x 10-4
8.
=
3
and
a
I\n
e + 1 (b/W) + a2 (b
[..,.,1
6.86922 x 10-2
a
-3.8,1-27 x 10-6
a4= -1.56500
x 10,:""7
b/W.
U
of the bend was found to nrotect
length
percent
')
~+
45
CompQr~son
indicates
of 'the 'two c(lrves roresenter1 in Fif';.4,.37
that groins
better performnnce
placed at the centre of the bend have
over those placed at ten percent upstream
of bEmd centre.
I
4.3 Effect of groin on banklerosion
I,
i'
Channel bank erosion wai3
, observed
groins,
whirling
due to the placemont
e)f
The cause of this erosion may be dUG to the flow causing
motion on the'backside
of the groin.
l'.:rosion
observed was found to be of two types (a) upstream
,
bank erosion, and (b) rlownstream bank erosion.
erosion was measured
B0th type's nf
frnm the initial bankline
along the length
of ",rain.
It was noted thot for small groin projections,
bank eroded.
the upstream
The length of this erosion W8S found to decrease
'increase in groin projection.
further incrensed
no erosion
occur. Also, the upstream
\I11engroin projection
of the upstream
with
r'1tio was
bank was found to
bank erosion was fOund to be greater
when the groin was placed at the centre of the bend, and to be
r
less when groins were place~j at ten percent upstream,for
having smaller projection
the erosion
ratio.As
the projection
groins
ratio increased
in both cases c1eoroased and there was almost no
erosion in the upstream
sidelwhen
( .•..
~
the ratio became little high.
46
Downstream
proiection
bank erosion was observed at the hiqher ~r:in
ratio. This erJision Was f'ouniJ
I
to be ;}ronounced for,
the groins placed at the ten percent upstream
of the centre
of
the bend.
4.4
Effect of groin on the ,cross sectional
The variation
of cross-section
area and velocity
at the bends where groins
were placed, variation
of' crass-section
the bend and variation
of cross-sections
at crossing upstream
at crossing
downstream
of the bend are shown in Figs. 4.25 to 4.36. The continu0us
line indicates
the cross section beforo placing
broken line indicates
the cross-section
Erosion was observsd
at theopposito
of
firm
of gr0in and the
after placing of groin.
bank of the ",rain side.
Little variC'tion of cross section at crossin!';were observed.
Placement
of !';roinat the concave bend resulted
of channel width and the sffectiv8
flow was thus increased
This increase
downward
in velocity
flow area. The velocity
since the disch~rqe
resulted
in the r~iJuction
of
was kept constant.
in scour of bed vertically
at the groin side bend ,and deep water
ch'1rtnelwas
-
shifted away from the bend. IThe deflected
and increased
at the bends may hav", lost its energy in scouring
toe forming vortex
and eddies and that maybe
current
around groin
the probable
reason for more or less stable nature of crossings(20).
'II
4.5 Scour at the toe of ~roin
It was observed th9.t in all the tests, scour holes were
formed at the toe of the groin. The plan area and pattern of
the scour hole, the maximum
scour depth were observed
i:
the tesc. It was found that the above features
.
during"
of the scour
halo, together with the scour:iconstant,
varied with tho variation
I
of projection
and loc"tion
and the relationship
following
4.5.1
of the groin. The variations
obtained
there from are discussed
observed
in the
sub-sections:
Effect of projection
Fiaures
te .13
of ~roin on the scour area and pattern
to 4.24 show the plan
ar0JR
and pattern of the
scour formed at the toe of the groin. Depth contours with an
inte~Tal
of 1 centimeter
groins tested.
scour
were 1rawn in the vicinity
of each
Tho outer contour line gives the bound8Ty
of the
area.
The size of the scour halos were found to increCtse with the
increase of Groin ~rojection
for both the groins placed at tho
bend centre and at ten percEmt upstream
the rate of increase
of bend centre. However,
in the two cases were different.To
ascertain
the trend of increase of scour.area with the increase of groin
projetion
tically.
ratio, the parameters
Best fil correlation
the best fit correlation
.'Ii.
II S
and b/W were analys8'1 ststis-
was calculated.
with equations.
Fig. 4.38 shows
For groins placed at
the centre of the bend tho equation takas the ferm.
48
=
AS
The correlation
0.06684(b/W)0.656
coefficient
was found to be 0.9638.
'i'he shape of the scour hole mny be observed
from Fie;s.4.13
to 4.24 to be a balloon shape with a bulge
at one corner and
pointing
The shape of these
towards
the downstream
diroction.
scour holes are more or less in agreement
by J\hmed(2). However
cases between
some difference
has been observed
in some
the shnpe of scour hOlGS formed but no definite
remnrk can be made frem the present
!J
with those obtained
strong vortex
structure,
study.
fromed at the tel,?of the groin
h8.ving vertiC'll axis of roto,tion, widened
the scour nreC1 with
the increase of ~roin projection.
From ~roins plnc0d nt ten percent upstream
relationship
between
of bend, the
the scour area and th," ,"roin Dro,jection
}~iie was fOund te be
1\
s
=
0.12108
The correlation
(b/W)0.4305
coefficient
...
in; this case was 0.9640.
'equations (4.3) and (4.4) may nbt be recommended
but they show the trend of variation
variation
of groin projection
4.5.2 Effect of projection
scour hole
Figure
(4.4)
Though
to be conclusive,
of scour area with the
ration and location.
of groin on tho depth of the
4.39 shows the rC-Jlntionship between
of scour hole and the groin projection
the maximum
depth
ratio. It was observed
49
that the non-dimensional
ds versus
plotting
of ds/W versus
b/';lshows a better correlation.
dent variable
Therefore,
of
the depen-
was chosen to be ds/W.
The maximum
the increment
b/W instead
depth of scour hole was found to increase with
of groin projoction
r'1tio, for the both cases
when groins were placed at bend centre and at ten percent
upstream
from bend centre.
The equations
relating
ds/W and'b/W
for best correlation
was found to be as follows:
For groins placed at bend centre
d s /W
The coefficient
=
0.03755
(b/1¥)0.22694 •••
of correlation
_
The coefficient
(b/W)0.35424
from bend centre
.••
(4.6)
of correl.')tion wets 0.6690.
In both the cases, the point of maximum
to occur at a little
downstream
of vortex
towards
direction.
the downstream
depth was found
from the toe of the groin due
to the combined action
depth-~or
(4.5)
was 0.6777.
For groins placed at ten percent upstream
d /w = 0.02412
s
...
structure
and flow velocity
Comparison
of the maximum
tho vwo cases shows that the observed
scoUr
scour depths for
50
both thE: cases
for
the
4.5.3
depth,
trend
of the
,
some projection
Effect
It
were almost
of groin
same order
ratio.
projection
on scour
was observed
thqtt the
when plotted
with ~ithe groin
to
increase
with
the
The relations~ips
correlation
are
constcmt.K.
SCour ccnstant,
increase
(Fig.4.40).
For .;roins
of m,w:nitUr1e
a me'1sure of scour
projection
ratio
of groin
obtained
for
prCljection
the
For groins
placed
at
tho
of correlation
:
for
at ,ten
,
4.40
groins
centr~
is
less
of the
bend for
form of
centre
of' the
bend:
than
the
...
(4.7)
w"s founc' to be 0.8825.
perccmt
I
upstream
of lnnd
+ 0.0,199 (b/~r)
;
it
lvaS 0.8582.
may be observed
placed
centrQ.
(4.8)
:
of correlation
From fip:ure
constcmt
f
placecl
K = 4.0822
The coefficient
best
r'1tio
as follows:
...
The coefficicmt
showed the
at
ten
percent
the value
for
pro ins
same projection.
th2t
value
uDstream
rlacerl
at
of SCour
of ben'!
the
centre
51
,I
4.6
Comparison
of pred.ict'ed
scour
I
The maximum r',epth ()f, scour
groins
were
tors.
J
Comp,",rison was m::v1 with
1'lhcn the
that
the
observer'! 'lt
compared witti' those
;\hme6., ::110 sla
maximum seal
obtained
in the
equo.tion
(Eqn.2.7)
depth
are
to the
prediction
obtainen
of the
given
investigaby Inglis,
close
eouation.
Results
l
in this
study
by Khosla's
2.6)
to the
in '1,greemcmt with
with' the
was compared l.;rith
(Eqn.
depth I'as obtained
in agreement
obtained
r'cpth
are very
Inp"lis
Also maximum scour
is
toe
by sever'll
tho bquati(ms
by In/:(liSlr equation,
specified
(20)
prer'!icted
the
and HossaiJ[.
predicted
results
depth
lower
was found
limit
obtained
the
was found
study.
present
as
study.
equatian
"
'rhe maximum scour
to be very
(Eqn.
that
from Ahmed's
from Hossain 's
present
equation
it
2.8).
high
compared
CHAPTERFIVE
CONCLUSION
~NDRECOMMEND~TION
5.1
Conclusion
A series
study
the
of tests
effects
in a bend.
The various
at
with
groin
thE) centre
of the
following
1.
\'Iith
the
conclusions
increase
protected
the
length
is
protected
percent
upstre'lm
downstream
value
stream
2.
There
of groin
exists
obtainerl
bend centre
. -;. r
;?/,. ,
" ~i.
each time.
one
10 pE)rcent upstream
in chapter
r,ttio,
and the
the
three,
downstream
placement
For groins
same trend
by ~roin
nltio
in this
tho
Bevond projection
decreases.
protected
case
for
is
is
placed
of 17%,
at
ten
of' v3riE'tion
found.
of
The maximum
of down-
23%.
I'd/wand
in 3greement
Moreover,
performance
of' the
ratio
maximum length
between
elata are
by Ahmed (1).
have better
at
when the
a good correlE\tion
(Eqn. 4.3 and 4.4)
results
located.
projection
protection
from 5 percent
nt two locations,
as rlescribed
of' bend centre,
len~th
groin
may be drawn.
increases
length
other
to
of a single
5 percent
were studied
study
laboratory
was vRried
of about
of~ projection
centrally
in the
ratio
bend and the
Based on the
the
groin
projection
pro jE)otions
out
and projecti0rt
an increase
of the
bond.
carried
of locQtion
The groin
to 30 percent
were
for
groins
the
b/W
wi th the
placed
protection
at
of
53
downstream lenpth
percent
3.
upstream
of the
of groin
projection
at
ten
scour
hole
for
increases
groins
placod
the
hoth at
tho c"mtre
lation
exists hotween
scour aroa and groin projection
ra tio.
The scour
formed at
area
rate
the groin
for
placed
The maximum depth
increases
placeiJ
fair
b....,th at
the
cpntro
at
~)Gnclcentre
of the
the
toe
bend contre.c
of the
()f .<::roin projection
a11'1"t
ten
hole
pcrccmt
groin
f()r groins
upstream.
,'?roin projections.
A
The IDnximumrlGpth of
has o"en observec1 t() be "lore in case
at
than
was c;btainGd bC0tweon the maximum d()pth of
scour
thebem
c<:mtre than
that
incClse of
of' ""rain
""roin located
10% upstr.2am of Ilend centre.
The values
groin
of sc',ur
projection
percent
constant
than
sCOur h010 at
increase
and different
ten
of
A good corre-
too of .c-roin increases
10% upstream
the
scour
at
at
tho
,"o;roins places
with
correla.tion
located
the
of bond centro.
increase
ton percent
a faster
upstroam
with
and at
for
5.
placement
of hend.
The area
at
4.
compured to the
for
for
upstream
greins
compated to
constant
groins
incrGases
placed
both at
of bend centre.
placed
at ten
the placement
at
Ivith
increase
bend contre
The valUes
percent
the
the
and
of scour
upstream
centro
of
of the
is
less
bend.
54
A good cor~elation
prOjection
ratio
between the
W8S
found for
SCOur constant
both
and groin
the loc"tions
of
groins.
5 .. 2 Recommendations for
The study
single
groin
of the
future
effect
study
of location
and projection
of a
in a bE'1d may be extenrlocl by incorporating
the
following.
1.
By using
different
2. By varying
size
of bed and hank material
the disch" rge Over a wide range
3. By changing eriontation
of ~rnin
with
respect
to
curvature.
4. By using
5.
groins
B,. applying
the
of various
tidal
shap,s
influence
and types
from .,ownstream.
bend
REFERENCES
1.
Abmad, M., "Spacing and projection
protect ion", Civil Engineering
London,March and April, 1951.
2.
[,nroad, E.,
dikGs" Proc.
and Public
"EXP"}l'imontson design
Minnesota Internqtional
IAHR, ASCE, Minneapolis
of sp).lrs for
Minnesota,
bank
vTorks Review,
and behavinur
Hydraulics
of spur
Convention,
U.S.t\.. September 1-4,1953.
3.
f,kikusa, I and K4kkawa, H, "Hydraulic Behaviour of the groins
in the streams", Ninth convention,
IAHR. Dubrovnik.YugoslaVia,
1961 •
4.
Bangladesh viater Develorment Board, "'\nnual Reports,HYdraulic
Research Laboratory,
1972, 1973, 1974 and 1976.
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Bangladesh 1.,rater Development Board, Persom:l
6.
Bler()h, T, Galay,
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V.J.
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2~d Ynremko E,K, "Observation
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slJUrs", Hivers
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Fort COllins,Colorado,U.S.A.
1976.
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Bush, J. I,.,
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9.
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12.
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1st
Pittsburgh,
Univ.
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Franco,
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0.,
for
Wallingford,
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F. and Skovgaard,
J.J.,
St<\tion,
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1967.
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l'luiil
Re,'.;"U lat ion,
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Mechariics,
Dyke Design"
,'.SGE, Vol. v1W3,
.I~,UP;.
14.
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rivers",
Vicksburg,
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portation
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meandering
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ProcGsses",
Processes
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iJiley
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tenionci8s
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9th
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235-249',
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1970 •
•
h
t.
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18, GiLL,
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98,
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No. HY9, !Paper 9198,
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,
1587-1602,
1972.
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C.V.,
training;
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I~,ehavi"ur,
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No. 60, ~8W Delhi,
and
India,
1971
II
20. Hossain,
M.M., "Study
by i:;roin"
]\1.Sc.]mgg.
Water Resources
21. Irrigation,
Thesis
bank stabilization
presented
Em;ineering,
Drainago
"Quarterly
of river
Bl!mT.,Dhaka,
and Floo,l C''''ltr0l
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Laho r ,~pril,
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January-March",
1969 •
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1981.
Reso'lrch
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lorna b::lSis stuc1.ies on Hyc1.rauJj,c
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[
22. Jansen,
Zanen, A.,
alluvial
"Principles
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Benrle"om, L.V.,
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24. Komura,S,
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ASCE, Vol.92,
terr:,
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depth
~o.
Proc. 14th congr",ss,
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ing I,imiteil, Lon'"on, 1979.
of scour
HY5, Paper
bed vari.",tion
the
]Vf.
in lon,,; constriction",
4898,
~t long
,I iUIH , Paris,
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1966.
constrictions",
Vol.3,
raper
C14,
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25. Lane,E.V/.,
1955.
26. Laursen,
"Design of stRole
E.]\1.,
No. HY2, Paper
"Scour
2369,
chbnnel",
Trans,
at
bridge
crossing",
pp.
39-54,
1960.
ASCE, Vol.120,
I'roc.llSCE,
Vol..86,
!
58
E.r1.,
27. La\- .'san,
Froc.
28.
fISC.E,Vo1.89,
Leopold,
L.B.,
\'lolnian M.G. aJd ]'I[iller,
29. r1anohar M, "Sea dofence
Journal
of Institution
May 1967.
Miller,
of
Na(':ai,
S., ";lrran.",sments
.
I
of watprltl,WS p.nd Harbor
pp. 93-118,1963.
J.P.,
"Fluvial
,
•
lns
Engineors,
H.M.,
("If
Flnd revetmont
London,
"Stabilization
HYdr. Divn.,
of' .",roins
Divn.,
34.
New H. A.,
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Pr'1c.
82,
Sept.,1956.
s"nc! particles
35.
river
0.
rotation",
Journal
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of HYdr. Divn.,
Nishat,
ii,
of alluvi20l
Thesis
presanted
UnivGrsity
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of
M.C.,
of Hydr.Divn.,
the
"jVjechanism of
due to
l'roc.liSCE,
channels
Department
Strathclyd.e,
Proc.
Journal
-;
"TrQnSV8rso :B'lowin
to
I\SCE,
on s".ndy beach",
!:SCE, Vol.
H,' "Mc)tion of
"it study
s" ,
Vol.47,
oGtween
.o:roins",
Journ3.1 of Waterw::ws and H'lrbo:>:'Divn.,
Vol.84,
No. 1'11'15,Jan. 1961.
33.
San
I,
I
Kubo,
scour",
I
I"
C.R. and Borland
32 . NEw;ai,Sand
..ridse
vi.IH.Freeman and Co.,
1>Torks,..gro
ani Murlr'lycrocks",
Journal
Vol. 89, No. HY1, Jan.1963.
31.
o,f relief
No. HY3,lljoaper3516,
process
in Goomorphology",
Fransisco,
U. S. A. 1964.
30.
ill
"fin anal,fsis
of
ASCE,
earth
s
Vol.93,
in regime",
Civil
f
Ph. D.
Enginoering,
U.K. 1981.
str"al'l
l.SGE, Vol.100,
flc".! meanrhrinp;",
No. h'Y6, June,
Journal
1974.
59
36.
Rahman, K.S.,
M.Sc.Engg.
Thesis
Resources
37.
38.
"A study
presented
Enginecring,
Raudkivi,A.J.,
on tIl::; ,,~obio;l
to
thc
Shahjahan,
controlling
M.,
"Factors
Ph.D.
Engineering,
July 1970.
Thesis
University
presented
Shen, H. 11'., "River ~l,,)cJlanics",
Colorado,
U.S.A.,
1971.
40.
Singh, B.,
odition,
"Fundamentals
the
to
the
2nd Edition
of
stream
Department
Glasgow,
Vol. I, and II,
of Irrirwtion
Nem Ghani! and Bros.;
of Water
geometry
of Strathclyde,
39.
Padma",
1978.
"Loose Boundary Hydraulics",
1976.
river
Department
BUET.,nhaka,
London Pergamon Press,
meanders",
of the
of
Civil
U.K.,
Fort
Collins.
Engin"oring",
Sixth
Roorkee,
India,
1979.
41. Tomlinson,
J .H., "Groynes in coast",l
EnP"g. a literature
Y and summ3.ry of rc ;omrnendec1pract
::e", Report NO..tT 19~
Hydraulics
Rese3Tch Sbtion.
vlallinpf'ord.
Enf,;land. March,19E"
SUrl
,
42.
United
East,
43.
Nations
"River
TraininF(
Sales
"Unpublished
report
No. 1953.
45.
Willj.s,
Roorkee,
J.C.,
I
Department
Gupta,
S.C.
United
Far
Nations.
Bangkck,1953.
of
different
of Water Resources,
1982.
and Gupta,
Works ", 3rd
India,
edition,
Il.L.,
"Theory and
Nem Chand and.
1977.
:::'oloffi2.n,ILL.
Study of transport
pp. 489-501,
1972.
F-6,
'on se(~imeAt analysis
Design of Irrigation
Bros.,
II,
BUET.,Dhaka, Juno,
n.s.,
Varshney,
Asia and the
and R'1nk Protection""
of Bangladesh",
Engineering,
44.
Economic Commission for
l~blications
rivers
.
of J'ine
and Ellis,
sand",
l'T.M. ,. "Laboratory
1'r'Jc. ASC"l,Vhl. 98,
No.HY3,
---.--
-~.-FLOW
FLOW
--
--..
hole
Ss_c_o~~
)
(
"-
(
'
r
~
I
I
\
\
"- "- ,
-
ANK LINE
Denehys groin
--...,
/,---,
/
/
/
\
(
I
\
//~--,~
,
,
I
Hockey
\
\
\
,
\
I
\
\
/
,
Fig. 2.1
.~
Different
types
I
(
groin
groin
(after'
Attracting
punmla and
/
/ Scour
hole
//
/
BANK
Deflecting
of
~
(
BANK
groin
//
/
I
\
Repelling
/
/
/
I
\
\
(
I
I
/ 4~ to
LINE
groin
lal
,
I
I
I
\
\
\
(
I
\
....
(
I
\
-", \
I
/
\
\
/
I
\
/
/
/
/'
/
,(Scour hole~\
\
~
,I
I
\
~
I
\
\
grOin
\
\
I
\
(
(
I
I
River
shape
,,
/
.-<'
Silt ing
1977 )
60°
Intake
tank
Automatic dry Sediment
Delivery
Point
FeeEler
line
gauge rail
10"Solid wall
~ Point gauge
II
5
Pervious
wall
Sand bed
Initial flow chamel
Point gauge
oint gallge rail .
Toil 'Jate
low meter
Loss line
Sand
In,itial
SECTION
Pump
bed
A-A
pipe
---------
Tail box
'I
•
3 dla
roller
Angle
I.
M.S.Channel
( 10'X 3")
/I
1r2 dlQ roller
Fig. 3.1 Experimental
set-up
I
• •
channel (8 X2)
Details joint
plate
9
o
N
o
6
o
o
o
N
o
I
i
,
II
\
2
,:,-:l
~
"
'I
I
'I
X
0
I,
00
I
<{
0::
3
w
<.:>
z
0
I
, I
I.
<.:>
z
0
<{
W
0::
X
5
UJ
0
z
w
Vl
3:
6
::.::
u
0
..J
U
7
8
9
Second
be nd
@
Deposition
Groin
CD
Average channel width= W
Downstream length protected= Ld
Scour
ale a = As .
Maxi mum
Fig. 4. 0
Definition
groins
Sketch
were
showing
placed
and
s.cour deplh=
location
of bends
the measured
ds
where
cross-'sections
I
,
,
I
30
I
Legend
Groin
25
c en tre
Bend
L ccat ion:
DIS
5'27 "10
project ion:
length
.
1-00
protected:
It
I
bank
As:
O'19B
fl2
ds:
0'223
fl
It
0'083
caving:
U/S
Thalweg
20
Thalweg
before
after
Deposilion
r
I
II
,
I
'11
\ Y;/
15
Groin
"
Bank
~ ~Bank
line
line
before
after
.~~
10
15
10
o
Fig.
4.1
Location,
Scale:Vt30
of
bank
Q=
line
thalweg
0' 03222
I
alld
cfs
deposit ion
for set ut
1
Legend
Groin projection',
Location:
35
Bend
10,38 0;.
centre
DIS
length
U/S
bank
caving:
As:
0'278
ft2
ds'.
0'2051'
protected'.
1'25
0,083
I
I
I
I
Thalweg
before
Thalweg
after
30
Deposition
Bank line
before
Bank
after
line
25
20
Fig,
4.2 Location
Scale:
of bank line
1130
thalweg
Q=0'03222
and
cfs
deposition
for set up
25
legend
Groin
location:
20
As:
0.543
d,s~
0'243'
DIS
length
U/S
bank
line
29%
cent re
Bend
Bank
Bank
20'
projection',
t t.'\.
prote ctee!,
caving:
Iine
0'0417
before
Thalweg
after ~
Thalweg
---- /'
tl
0.917'
/
before
after
,
15
De po siti on-
':,
_lJ
10
7.5
10
o
Fig.
4 ,3
Location
Scale:
0f
1:30,
thalweg
, bank
Q=0.03222cfs
/ \.
Iine
15
an d d eposi ti on for set up
2
I
L'ege n d
Groin
15-59.1.
projection;
Location'.
Bend
DIS
.
I e ngth
tJ/S
bank
As:
0'458
centre
1.4 3' .
protec t e d :
1
dl~.
I '
1\2
0.246
45
before
Thalweg
____
----L
after
Thalweg
H
Deposit ion
0.0417
caving:
I.
Bank
line
be fore
Bank
line
after
t.LGroin
40
35
Fig.
4.4
Location
Scale:
30
of
1:30,
bank
line.
Q=0.03222
thalweg
cfs
and
deposition
for
I
set
up
2
Legend
Groin projection:
40
Location:
24- 65 0/0
Bend
centre
DIS
length
U/S
bank
caving:
As:
0'4'58
ft2
I
protected:
1.08
0-\25'
• s ~ 1- 4 33 I
II
ank
line
before
Bank
line
after
3S
Deposi lion
Thalweg
before
Thalweg
alter
/
/
I~
I
30
I
I
Groin
\\;/ 1->
\
\
\
\
\
\
25
Fig.
4.5
Location
Scale:
20
of bank line, thalweg
1:30,
Q= 0.03222
and
cfs
deposition
for
set
up 3
Legwnd
Groin
projection:
29'89.1.
Location:
Bend
As:
O'527B .ft2
30
ds:
DIS
U/S
0.24609
lEngth
protected;
bank
caving:
25
I
I
I
I
,
centre
'
Deposition
I
l{)0
0.0417
Bank
line
before
Bank
line
aft er
/~
I.
I
I
I
94
4»
I
I
\
Groin
\
Y
\
20
.\
\
'Thalweg
before
'Thalweg
alter
\
\
\
\
\
\
I
I
IS
Fig.
1..6
Location
Scale:
of
bank line, thalweg
1: 30.
:l?~
'I
,J
,,
I
i
Q =0. 032'22 cfs
and
deposition
for set up 3
Legend
Groin" projection:
Location:
DIS
10%
length
5'07%
LJ/S
LJ/S bank cavin9:
20
0'1,167
protected:
As:
0'251,
fl2
ds:
0'236
ft
It
It
0'1,58
Thalweg
before
Thalweg
after
15
Deposition
Bank
line
after
10
Bank
o
I ine
15
10
Fig.
1,.7
Location
Scale:
of
1: 30,
bank
line,
thalwey
Q= O' 03222
cfs
before
and
deposition
.for set
up I,
Legend
30
Groin
projection:
Location:
10-42 '10
10 '10 U/S
DIS
length
protectedl
U/S
bank
As:
0.322
ft2
ds:
0.193
ft
caving:
0 -575
O. 0833
It
ft
2S
Deposition
Thalweg
before
Thalweg
after
(
14
20
I
...-U.
J
»
I
Groin
t
\/
\
.
Sa n k line
Bank
line
after
before
15
Fig.
4.8.
Location
Scale:
10
of bank line
1:30
J
thalWll9 and deposition
Q-0'03222
cfs
for set up
4
Legend
40
Groin
proj ect ion:
Location:
10%
DIS len']t h
UIS
bank
As:
0-374
ds :
0'207
15 - 28 %
U/S
protected:
caving:
0-5'03
ft
0'188
ft 2
35
Deposi tion
Thalwe']
before
Thalweg
after
7
/-......J.J
f
I -
LL
30
I
Groin
--LI
I
Bank
line
before
:):>
\
Bank
line
after
- 25
Fig.
4.9
Location
Scale:
20
of
1:30,
thalweg,
bank
Q= 0-03222
line and deposition
cfs
for set up
5
,
\;
:>0
t
:
Legen d
,I
Groin
100;. U/S
Location
O' 0417
It
halweg
before
caving:
U/S
bank
As:
0.434
O' 67 tt
protected:
DIS length
45
19.87 0;.
project ion;
tt2
ds : O' 236
Thalweg
after
40
Deposition
JJ
Groin
", s\
\7
Bank
line
be fore
line
after
35
30
Fig.
4.10
Locat ion
deposit.ion
Scale:
25
of
bank
for set
1: 30,
line
.
thalweg .
up .5
0.= 0.03222
cfs
and
Bank line
\
Bank Iine alter
.\
y\
\
\
\
\
\
Thalweg
before
'Thalweg
alter-----
...•.•.
\
\
II..!-
~
Scour
I
I
I
I
Groin
Deposition
I
I
I
I
I
I.?-/
/
I
/
./
./
./
Legend
Groin project ion:
Location:
Fig.
4.11
Location
Scale:
of
1: 12
bank line,
Q=
thalweg
0{)3222
cIs
25 %
10% U/S
DIS length
protected:
As:
0.461
It ~
CIs:
0'246
It
and
deposition
0.813 ft
for set up
6
,
Legend
Groin
projection:
Locat ion;
30.13 0;.
100;. U/S
DIS
Len~th
U/S
bank
As:
0.575
It 2
ds:
0.246
It
O' 521 ft
protected:
caving -
0
I
I
/
{
I
I
before
I
I
./
./
I
./
/
IL-Sank
///
/
././
.
Bank Ime
before
1-Thalwey
after
line
after
I
I
I
/~
I
Groin
u!:-
I~
I
cour
I
I
Deposition
I
I
I
I
\
\Y
\
\
\
\
\
" ~~,
\
"
~\
\
"- \
\
\
\
\
Fig.
4.12
Location
Scale:
of
1',12,
~
\
\
bank
a=
line
thalwey
O. 03222 . cfs
and
deposit ion for set up
6
3.0
CONTOURS
I Contour
in terval.
1 cmI
, :,1'
", ;"
DIRECTION
OF
FLOW
BANK
Projection:
5. 270/0
Location:
Bend
centre
U/S
bank
cav ing: 0'083'
DIS length
protected
As: 0'198 It 2
ds', 0.223'
FIG.
4.13
SCOUR.
PATTERN
SCALE :1:1,
AROUND
(Q = 0.03222
GROIN,
cfs)
SET
1
1'00'
t
DIRECTION OF FLOW
DEPTH
CONTOURS
(Contour
interval
1 cm)
I
o
M
0
~
GROIN
BANK
Projection:
Location:
Bend
centre
VIS bank cav ing:
0.083'
DIS length
FIG.
4.14 SCOUR
SCALE:
PATTERN AROUND
1:2.
( Q= 0.03222
GROIN,
cfs)
10.38 %
As:
0.278
ds:
0.206'
SET
protected:
ft2
•
1.25'
•
DEPTH
(Contour
. DIRECTION
OF
CONTOURS
interval
1 cm)
FL OW
BANK
,GROIN
15.690/0
Projection:
FIG.
4.15
SCOUR
SCALE:
PATTERN
1:2
',/\
Location;
bend
U/S
bank
caving:
DIS
length
protected'
As:
O. 456
ft2
ds:
0 ~2 46
AROUND
((1=0'03222
GROIN,
cfs)
centre
0.0417
I
SET
2
t
1'433'
DEPTH
CONTOURS
(Contour
interval
1 cm )
1
DIRECTION OF
FLOW
GROIN
r,J
Projection:
20-29 of.
Location:
bend
UfS bank caving:
FIG.
4.16
centre
0-0417'
DfS length
protected:
As:
0-543
It 2
ds~
0.243'
SCOUR
PATTERN
SCALE;
1:2
AROUND
(Q-0.03222
0-917
GROIN, SET .2
cIs)
I
DIRECTION
DEPTH
OF FLOW
3.0
(Contour
CONTOURS
interval
1 em)
GROIN
ProJection:
24.55°/.
Location:
Bend
centre
U/S
bank
caving:
0/5
length
protect:
As:
0.581
ft2
.
I
0.125
I
ds:
FIG.
4.17
1.083
0'249
SCOUR
PATTERN
SCALE:
1:2
,
AROUND
I Q= 0'03222
GROjN.
.cfs)
SET
3
DIRECTION
I
OF
DEPTH
(Contour
CONTOURS
1 c m)
interval
FLOW
GROIN
FIG.
4-18
SCOUR
PATTERN
,
SCALE:
1: 2,
( Q =0
Projection:
29'87"10
Location:
Bend
UlS
bank
caving:
DIS
length
As:
0-5203
ds:
0.246'
AROUND
03222
GROIN,
c fs )
centre
0-04'7"
protected:
ft2
SET
3
I-DO'
DEPTH
(Contour
DIRECTION OF
CONTOURS
interval
lcm)
FLOW
BANK
Project ion:
5. 07 .,.
10"10 UIS from
Location:
FIG.
4.19
SCOUR
PATTERN
SCALE:
1:2,
(Q
UlS
bank
DIS
length
protected:
ASI
0'254
tt'
ds:
0.234'
AROUND
= 0'03222
caving:
GROIN, SET
bend
centre
0'458'
0'417'
4
cfs)
\
I
I
i,1, CONTOURS
-DEPTH
( Contour
DIRECTION OF
I' interval
,.'" I
1 cm)
FLOW
BANK
GROIN
10' 42°/.
Projection:
10 °/. U/S from
Location:
UlS
bank
DIS
l.ength
protected
As;
0'322
,
ft2
bs; .0'194.
FIG.
4.20
SCOUR
SCALE:
cQving:
I
PATTERN'
1:2,(Q=O'03222
O' 083'
I'
0575'
I'
,
AROUND
I:bend centre
I
GROfN,
cfs)
I
I
SET
,II
'I
4
DEPTH
CONTOURS
(Contour
DIRECTION
OF
interval
, cm)
FLOW
BANK
Proj~ction:
Location:
~
FIG.
4.21
100/.
UlS from
VIS
bonk
DIS
length
protected:
As:
0'374
ft2
ds:
0'207'
SCOUR
PATTERN
AROUND
GROIN,
SCALE:
1:2,
0.03222
cfs)
(0.=
_ .15 28"10
caving:
SET
5
bend
0.409'
"273
,
centre
DEPTH
(interval
,
DIRECTION
OF
FLOW
BANK
GROIN
3.0
Proje ction:
19.870/.,
Location:
10./0
U/S
bank
D/S
length
As;
0'434
ds:
0.23 5'
FIG.
U/S
caving:
from
bend
centre
0'0417'
protected:
0.57'
ft2
4.22 SCOUR
SCALE:
PATTERN
AROUND
1:2, (Q= 0.03222
cfs)
GROIN,
SET
5
CONTOURS
1 cm)
DEPTH
CONTOURS
(Contour
in'terval
1 c m)
25°/0
Projection:
Location:
,10°10 U/S from bend centre
DIS
length
As:
0-461
ds:
O. 246 '
protected:
0-813'
tt2
GROIN
._--
FIG.
:;-i:f
4.23
SCOUR
PATTERN
AROUND
GROIN, SET
SCALE: t~2, (Q = 0'03222
cfs)
6
.-
-;--
DIRECTION
OF
. DEPTH
FLOW
3.
CONTOURS
(Contour
interval
1 cm)
GROIN
Project ion:
FIG.
4.24
SCOUR
S CAL E:
Location:
100/0 U/S from
DIS
length
protected:
As:'
0-575
ft2
ds:
0'246'
PATTERN
1:2
30'130/0
AROUND
( Q = 0.03 22 2
GROIN.
cis)
bend centre
0.521'
,SEJ
6
LJ:
After
placing
r-.
pi"",
B,lo"
~-
7j'll.,-
~
"-- - - ~
~~
-- -
~
-
-
-
-
After
''ii'
=
--
3-3
SECTION
GROIN
ce:--.'
BANK
placing
Before
placir:1g
BANK
__ :..._ -=- _ ----=-_ -== .:::-::::_~
,
--
\
\
'-,--~~
1-1
SECTION
After
~
~'-::.
WB'." :'0"'_.
--
~ _as;:::
SECTION
FIG_ 4;25 VARIATION
(SCALE:
placing
OF
1:5)
(Q
CROSS
-
SECTION
0-03222
cfs)
BEFORE
AND
>~>~~
2- 2
AFTER
PLACEMENT
OF
GROIN,
SETUP
1
J......,~~::-r
After
Before
.;.y.
- ~--\'-=-~-- -
----
,-
l
",
"
-1"--"
- ---
;ot _
--.=::-
_.--- --
v
-= :: -:--.,---- - - - - - - - - -
-
VARIATION
(SCALE:
OF
1:5)
=
CROSS-SECTION
(Q=
4-'4
.-
--
SECTION
FIG. 4.25
I::
K
~
SE CTiO N
'-
r~~-
5-6
~---
"'V"
'\
=---'
_--- -::c-
After plae Ing
Before plae ing
N
i
plae Ing BAN K
------
--SECTION
iGROI
~lo.cing
O'03222cfs)
BEFORE
0:
1
After placing
Before placing
BANK
_
.. -
-..:.-ll>'-.:.. __
_;::;;::_~=_=_=_:=:_:;::::;-==;::;::::===?'.:._--
.,-",,---
~ __
5-5
AND
AFTER
PLACEMENT
OF
GROIN.
SET UP 1
\i
~
__~_
~~~
------
After
placing
. BANK
__ ~ __gJ~_-_[=-_~:~:
s]:
placing
~---
SECTION
3-3
I
-----
-------
..••..
,-
'.,101--""--
--
SECTION
After
placing
Before
plac ing
._--
---~
~
~
(SCALE:
1:5)[ Q= 0.03222
?
/-
---- L .--'" -
r
placing
BANK
---"'"
SECTION,
CROSS-
-,
placing
--OF
'/
I~-
",
Before
FIG. 4.27 VARIATION
BANK
,
1-1
After
--
"" •.•.
GROIN
SECTION
cf5)
BEFORE
2-2
AND
AFTER
PLACEMENT
OF
GROIN,
SETUP
2
r-
"'-,
I
I
" '-~i
"17
--...
<
- - -
.SECTION
~-G
t
After
placing
Before
placing_4;ji
J
- -,
-_----..-
I
BANK
>i ~/ -,,..--
6-6
-~r-.-~A
ROIN
f ter plQc~ing
r
7'J1
Before
plac ing
,BANK
t
'<7
~=
J
~
",
-- -
-
--
///
~
~//
SECTION
//
"'-...::__
v_
FIG. 4',28 VARIATION
(SCALE:
OF
CROSS
1:5)(Q=0.03222
SECTION
cfs)
,"""-
~ ======;.,=-
placing
BANK
~PlaCing
~=======",.d-,-,.J.?,i« ..r.:+
r
-----.. - -- =-:---::-- - -- - -:- ~ - SECTION
~~-...'"
...:::
4- 4
After
'•••",,-
.~
~ -- - - - - -
~ 5-5
BEFORE
AND AFTER
PLACEMENT
OF.
GROIN,
SETUP
=~rf""
2
j
~
-=_~
~_____
Afler
=__~j_[_~e:~~e_PlaC~ng_c_
SECTION
placing
- Before
~~
GROIN
piaci ng
<-~-
SECTION
,(-BANK
3-3
Afler
-..-1
placing
~-
,
/
~
/
1-1
At ter plac i ng
Before placing
BANK
-a.~
-- ----
--
=
SECTION
FIG.
4.29
VARIATION
(SCALE:
OF CROSS
SECTION
1:5) ( Q= O' 03222
cfs)
BEFORF
==--~~-~---------~------ ~---'
."....-
2-2
AND
AFTER
PLACEMENT
OF GROIN,
SET UP
3
""'"
_=
y'
-
...
--.......
f
=-
d
----
---SECTION
Aft"
_
Before
P"""]
~K
Pla~ng
;;'
6-6
ROIN
r
-- ,
After
Before
placing
-
------..........
•
--, ~
~
SECTION
4-4
~
Aft"
ANK
~
----- t ----- ----
piociog
cC
ANK
-'-=~='==~'*"
e
~_
_
V
........
__
FIG. 4.30 VARIATION
OF
CROSS - SECTION
1:5) (Q- 0'03222
cfs)
Before
.
...,>
SECTION
(SCALE:
placing
BEFORE
:::
..;-_,...==
....
pia cing
~
Q
4
_"'"1--"
5-5
AND
AFTER
PLACEMENT
OF GROIN
SETUP
3
r-""",,-
I~---After
r-
--,
'-
---
,I
placing
Before
r-,,..-
BANK
placing
--=-=
--SECTION
GROIN
.~~
-~'
3- 3
Afte,_ placing
Before placing
-BANK
-""-
---- --
f.t;
/"
/"
,
/"
~,
/"
....•.....•••
--
,.."./
_/
SECTION
1-1
C't
_____ __ "'. __ ~ .' :I:I:
After
placing
B,f",
h~
plooiog
------SECTION
FIG.
4.31 VARIATION
(SCALE:
OF
1:5)
CROSS-
[Q-0-03222
SECTION
cfs)
'2-
BEFORE
2
AND
AFTER
PLACEMENT
OF
,GROIN,
SETUP
4
lE:d"cm
g
--.....
;;.~~
'"_
...••••1::7"_-_
~
="
-=-;::;;p
_ __
__ __ ____
-~sz
~.
__
Before
£A':"___
_~=-"
placln;)
--
SECTION
6-6
GROIN
After placing
Before plac ing
~--------"
/'
/
-- -
/'
'"
/'
SECTION
-.., --
-
lJ
•
,BANK
~
--• -/
~=~~t:;::===~~"'S7;::::===::;;::::~~~=~~===-,_?-
== =
--::.:
1..32 VARIATION
(SCAl
4-4
After placing
Before placing
=._?_~O::-
SECTION
FIG.
BANK
E :,:
OF CROSS-SECTION
5 ) (Q=
0'03222 cts )
BEFORE
5-5
AND AFTER
PLACEMENT
OF
GROIN,
SET
UP
4
14
rAfter
--.-__
~~
~_'.
~ ~~.j
... - - /"
placing
'CBefore
----=::..:- ~~.---~~~-
Placing~:rB~NK
- -' - - - - SECTION
-
- - -
~
3-3
GROIN
placing
~BANK
lIlefore plac ing .
- =--=---;..../
•
"
,
/
-_/
"
//
-
------
/
SECTION
1-1
After
placing
Before plac ing
.,.........
~...:-=.=:-"
FIG,
4.33
-
--.-
VARIATION
( SCALE:
...--
OF
CROSS- SECTION
1: 5 ) . ( Q = O. 0 3 222
.....
_-_
.........•...•
....
_:::==.--;::--_ -~'
-- -.-
SECTION
2-2
BEFORE
AND
c fs )
BANK
AFTER
PLACEMENT
OF
GROIN
~
SETUP 5
~r-~..,...
After
placing
Before
placing'
BANK
..•• - - -- --- ----
---
=
------
SECTION
--~~~
----6-6
GROIN
After
placing
Before
,
~~
--, --- -
~
---
------
-"
~
..- ..-
SECTION
'::
~
~---
SECTION
FIG.
4.3141 VARIATION
(SCALE:
1:5)
OF
CROSS(Q
SECTION
= O' 03222
r""""-
--- ---
~
4- Ii
"?Il"'-_"'<=::::::====:::::=="'====;:;======<::o==:_:::::-_=-,~_,",*_._.~~-
----
BANK
placing
cfs)
:dJ
After
placing
~ 3 e for e pia c i n g
-~-
-----
-"
cJ:'--,.~~
NK
•••••
------------
5-5
BEFORE
AND
AFTER
PLACEMENT
OF
GROIN,
SETUP
5
- --
\... _""'\
<-
-
-
~=~,....
rC
BAN"
~",i09
.~"'i09"
:=:;!:;::- -.
".
SECTION
__
3- 3
Afler
Before
placing
placing
----,
--
~,,
,,
'---
SECTION
--- ---
---
GROIN
--
./
1- 1
A tter plac ing
BANK
Before plac ing
-""""
- - -..1_
-
--_.....
-
...• - .•.•
,
--
SECTION
FIG.
4.35
VARIATION
(SCALE:
0 F
1:5)
CROSS
SECTION
(Q= 0"03 222
r-..-....•
-
~..::r-_-~-=-_-=
.••...,...,,/
BEFORE
2-2
AND
AFTER
PLAC,EMENT
OF
GROIN,
SETUP
6
cfs)
/
--..-,
[Be,oc<
q
5-5
SECTION
plociog
Before
r--- Af ler
\
II
~BANK
placing
placing
,-
GROIN
!
••..-~
,
--
:::_--
-
wAf'
"
-=-- _~ C,~e,oc~c
plcc'"g
VARIATION
('SCALE:
OF
1:5)
CROSS-
( Q -
--
----
~~
- -- -- -
/
//
/
r,"",
_ __
I
:A NK
5- 5
SECTION
0, 03222
=
----
SECTION
4.36
,,
9
i0 ____
.• .--
FIG.
,
4- 4
SECTION
_~,="
r BANK
/A<"';;;Z:
BEFORE
cfs)
,
AND
AFTER
PLACEMENT
OF
GROIN,
SETUP
5
O.g
0,8
,.
,I
0-7
0
Groin
at
11:>
Groin
at DOlo uls from
bend
centre
bend
centre
r
>
r;/
..
0.6
Eqn.
4.1
t
Ld/w
0.3
o
0.2
Eqn
4.2
o1
o
o
5
10
15
FIG. 4.37 RELATIONSHIP
STREAM-
20
25
---<.-b/w ( p ercenlage J
BETWEEN
LENGTH
GROIN
PROTECTED
30 '
PROJECTION AND
3
DOWN
10
3
o
Groin
at
end
A
Groin
at
0.1. u/s
... ------.
,
~
~----
centre
----- --_
from
..
ben
_------
centre
-------
0-656
b
..As-o.D6684(-)
1.0
( )'- 0.9638 )
t
0'4305
b
As= Q.12108 (Vi )
( 'r- 0.9640 )
001
3
1.0
10
30
-~~
FIG.
4.38
RELATIONSHIP
SCOUR
AREA
BETWEEN
GROIN
00
b/w (percentage)
PROJECTION
AND
fa
o
Groin
ll:..
Groin
at
at
bend
centre
10 0/0 u/s
from
bend
centre
,I
I
3
I
5
I
0-2269
-= 0.0 3'755 (l!.w I
"'(=0'6777
)
0-'
t
ds
.
0'35424
ds
02442(~1
-=
w
(y=
,.
.~
690 I
_I
0-03
-01
30
1
3
1.0
--~
•••
-: blw ( percentage I
I
FIG.
4.39
RELATIONSHIP
(Q =
0-03222
BETWEEN
cfs)
.L
SCOUR AND
GROIN
,
PROJECTION
I
I
9
8
-
7
K= 4-9404+0'02812
(J' =
6
0'8825
b
v;-
)
5
A
t
K
• (,-,.:",.
~01999 ~
(t =0.8582)
3
(
o
Groin
at
bend
A
Groin
at
10
0'0
centre
u/s
from
bend
centre
2
1
(l'
o
10
5
15
20
--
FIG-
4.40
RELATIONSHIP"
SCOUR
BETwEEN
CONSTANT
I Q-
25
.30
...•••••
~ b/w I percentage )
GROIN PROJECTION AND
O. 03222
~f
35
105
Table - 1
Set up
'Section
: 1
: 1-1
Initial c~annel
Discharge
Groin projection
Groin Location
5.27%
Before groin
Bend centre Placing
1. Slope
0.00101
2. ~rojection,ft.
3. Channel width,
After groin
placing
0.00167
0.12500
ft.
3.50000
4.25000
4. Area of cross-section,sft.
0.07639
0.11806
5. Maximum
depth of flow, ft.
0.24166
0.41666
6. Average
depth of flow, ft.
0.02183
0.02778
0.42178
0.27291
3.52690
4.42913
0.02166
0.02666
15.74803
14. 76378
19.68504
20 . 66929
13.50000
12.500000
1.16652
1.18110
1.45815
1 .65354
,0.00137
0.00278
power,ft-lb/sec.ft.
0.00203
0.00336
Qepth to width ratio
0.03333
0.04902
0.50307
0.28855
1 .78571
1.47059
0.00859
0.01962
7. Average velocity
of flow,fps.
8, Wetted perimeter, ft.
9. Hydraulic
10. Meander
•
810pe :0.00333
:0.0322 cfs
radius, ft.
length, ft.
11.
Meander
thalwe6 len~th,ft.
12.
Chan 81 length, ft.
13. Channel
sinuosity
14. Thalweg
sinuosity
15. Shear stress, pound/sft.
16.
Stream
17. Maximum
18. Froude Number
19. Relative radius of curvature
20. Mannings roughness
co-efficient
21.
Maximum
scour depth, ft.
0.22310
106
Table 1 (Contd.)
Set up : 1
Section:
Initial channel slope: 0.00333
Discharge
0.0322 cfs
1-1
Groin projection
Groin Location
5.27%
Bend centre
22. Plan area of scour, sft.
23. Downstream length:
protected, ft.
.
24. Upstream bank caving
25. Scour constant,K
Before groin
Placing
After groin
placing
0.19800
1.00000
0.08333
~.
26. Downstream length protected/
projection
27. Upstream bank/projection
5.15956
8.00000
0.66667
28. Downstroam length protected/
1"id th
29. Maximum scour depth/width
0.23529
0.05245
107
Table ~ 2
Set up
1
Section: 4-4
Groin projection
Groin Location
Initi 1 channel slop'
Discharge
10,3%
Bend centre
1. Slope
•
Before groin
placing
0.00333
0.03222 cfs
Aftel"groin
placing
0.00101
0.00167
2. ?rojection,ft,
0.22917
3. Channel width,ft,
4.00000
3.75000
4. Area of cross-section,sft.
0.11111
0.14410
5. Maximum depth of flow,ft.
0.10500
0.19667
6. Average depth of flow,ft.
0.02778
0.03843
7. Average velocity of flow,fps.
0.28998 ..
0.22359
8. Wetted perimeter, ft.
4.10105
3.95341
9. Hydraulic radius,ft.
0.02709
0.03645
10. Meander length,ft,
14..
76278
14.76378
11 '.Meander thalwe,; len"th, ft.
18.70079
19.68504
12. Char 'el lenMh,
12.00000
12.50000
13. Channel sinuosity
1 .23032
1.18110
14. Thalweg sinuosity
1.55840
1.57480
15. Shear stress,pound/sft.
0.00171
0.00380
16. Stream power,ft-lb/sec.ft.
0.00203
0.00336
17. MaXimum depth to width ratio
0.02625
0.05245
18. Froude Number
0.30660
0.20100
19. Relative radius of curvature
1 .06250
1
ft.
20. Mannings roughness co-efficient 0.01451
21. Maximum scour depth, ft.
22. Plan area of scour,sft.
.13333
0.01987
0.20609
0.27800
•
,-
108
Table - 2 (Contd.)
Set up : 1
Section: 4-4
Initial channel slope. 0.00333
Discharge
0.03222 cfs
Groin projection: 10.3%
Groin Location
Bend centre
Before groin
placing
After groin
placing
23. Downstream length
protected, ft.
1.25000
24. Upstream bank caving
0.08333
25. Scour constant,K
5.21186
26. Downstream protected/
proj(Jction
5.45455
27. Upstroam bank caVing/
projection
0.36364
28. Downstream length
protected/Width
0.33333
29. Maximum scour depth/Width
0.05496
..
:' ....
,
.1
!
109
Table - 3
Set up : 2
Section: 1-1
Initial channeJ~ slope: 0.00333
Discharge
0.03222 cfs
Groin projection: 15.69%
Groin Loc,c,.tion Bend centre
Before groin
Placing
After groin
placing
0.00101
0.00167
3. Channel Width,ft.
0.33333
3.25000
4.08333
4. Area of cross-section,sft.
0.10938
0.18264
5. Maximum depth of flow,ft.
0.10499
0.24934
6. Avera~e depth of flow, ft.
0.03366
0.04473
7. Average velocity of flow,fps.
0.29457
0.17641
8. Wetted perimeter, ft.
3.31365
4.26509
9. Hydraulic radius,ft.
0.03301
0.03282
10. Meander length,ft.
12.79528
15.05906
11. Meander thalweg length,ft.
16.73228
19.68504
12. Cha_Jlellength,ft.
12.00000
13.25000
13. Channel sinuosity
1.06627
1.13653
14. Thalweg sinuosity
1.39436
1.48566
15. Shear stress,pound/sft.
0.00208
0.00446
16. Stream power,ft-Ib/sec.ft.
0.00203
0.00336
17. Maximum depth to width ratio
0.03230
0.06106
18. Froude Number
0,28295
0.14699
19. Relative radius of curvature
1.53846
1 .22449
20. Mannings roughness
co-efficient
0.01631
0.03169
1. Slope
2. Projection,ft.
21. Maximum sc{)ur dopth,.ft.
n.24606
il
~I:
110
Tablel,- 3 (Contd.)
111
Sot up : 2
Section: 1-1
Initial channei
.Discharge
Groin projection
Groin Location
15.69%
: Ben~ contro
slope: 0.00333
0,03222 cfs •
Beforo groin
placing
After groin
placing
22. Plan aroa of sc"ur~' sft.
0.45800
23. Downstroam length
protocted, ft.
1.43333
24. Upstream
5.41451
,
bank caving
25. Scour constant,K
5.41451
26. D:n,rnstreamlongth,
protected/projection
5.50005
27. CUpstream
projection
28.
29.
'I
bank caving/
Downstream
width
Maximum
!
,
0.12501
length proiected/
0.35102
scour depth/width
.,
0.06206
111
Table -..!
Set up : 2
Section: 4-4
Groin projection
Groin Locp.tion
Initial chPJmel slope: 0.00333
Discharge
0.03222 cfs
20.29%
Bend centre
1. Slope
Before groin
placing
f,ftergroin
Placing
0.00236
0.00203
2. Projection,ft.
0.58333
3. Channel width,ft.
3.16667
3.16667
4. Area of cross-section,sft.
0.12674
0.23958
5. Maximum depth of flow, ft.
6. Average depth of flow, ft.
0.10302
0.24278
0.04002
0.07566
7. Average velocity of flow,fps.
8. Wetted perimeter, ft ~
0.25422
0.13449
3.28084
3.31365
9. Hydraulic radius,ft.
0.03863
0.07230
10. Meander length, ft.
11, Me J.derthalweg length, ft.
9.84252
10.82677
12.30315
13.28740
8.50000
9.25000
1.17046
14. Thalweg sinu0sity
1.15974
1.4,n43
15. Shear stress,pound/sft.
0.00569
16. Stream power,ft-lb/sec.ft.
0.00474
0.00408
17. Maximum depth to width,ratio
0.03253
0.07667
18. Froude Number
0.22395
19. Relative radius of curvature
1.10526
1.10526
20. Mannings roughness
co-efficient
0.03210
0.08564
12. Channel length,ft.
13. Channel sinuosity
21. Maximum scour depth,ft.
1 .43648
0.00916
0.08616
0.24278
11 2
Table - 4 (Contd.)
Setup : 2
Section: 4-4
Groin projection
Groin Locfltion
Initial channel slop~: 0.00333
Disch2.rge
0.03222 cfs
20.29%
Bend centre
Before groin
placing
22. Plan area of scour, sft.
After groin
placing
0.54250
23. Downstream length
protected, ft.
0.91667
24. Upstream bank caving
0.04167
25. Scour constant,K
5.25016
26. Downstream len!':thprotected/
projection
1. 57144
27. Upstream bank caving/project
0.07143
28. Downstream length protected/width-
0.20745
29. Maximum scour depth/Width
0.07571
11 3
Table - 5
Set up : 3
InitL.l channel
Discharge
Sect ion: 1-1
Groin projection
Groin Location
slop
Before gr0in
Bend centre placing
0.00333
0.03222
cfs
After groin
placing
1. Slope
0.00236
2. I'rojection,ft.
0.72917
3. Channel
3.50000
3.58333
4. Area of cross-section,sft.
0.09722
0.20660
5. Maximum
depth
0.08202
0.22310
6. Average
depth of flow,ft.
0.02778
0.05766
width, ft.
of flow, ft.
7. Average velocity
of flow,fps.
0.00203
0.33141
8. Wetted perimeter,ft.
3.58842
3.77297
9. Hydraulic
0.02709
0.05476
radius, ft.
10. Meander
length,ft.
10.33465
9.84252
11. Meander
thalweg
12.30315
12.30315
12. Ch,nnel
length,ft.
9.00000
1 .124.86
13. Channel
sinuosity
1.14829
1 .40607
14. Thalweg
sinuosity
1.36702
1 .40607
15. Shear strGss,pound/sft.
0.00399
0.00694
16. 8tream power,
0.00474
0.00408
0.02343
0.06226
0.35041
0.11445
1.28571
1 .25582
0.01941
0.06131
17. Maximum
length,ft.
ft-lb/sGc.ft.
depth to width
r~tio
18. Froude Number
19. Relative
radius
of curv'1ture
20. Mannings rou~hness
co-efficient
21. M'J.ximumscour depth,ft.
0.24934
11 4
T.iJ.ble-5 (Contd. )
Set up : 3
Section:
Initial channel
Discharge
1-1
Groin projection
Groin Location
2,'1.65~
.Bend centre
slope: 0.00333
0.03222 cfs
Bofore groin
placing
jlfter groin
placing
22. Plan area of scour,sft.
0.58140
23. Downstream
1 .08333
24. Upstream
length protected,ft.
bank caving
25. Scour constant,K
26. Downstream
projection
27. Upstream
29. Maximum
').76622
len~th protected/
1 .48570
bank caving/projection
28. Downstream
0.12500
length projected/width
scour depth,hlidth
0.17143
0.30232
0.08428
115
Table - 6
Set up : 3
Sectio,,: 4-4
Initial channel slope: 0.00333
Discharge
0.03222 cfs
Groin projection
-29.89%
Groin Location
: Bend centre
1. Slope
2. Projection, ft.
Before groin
placing
0.00236
3. Channel width,ft.
1.08333
3.91667
4. Area of cross-scction,sft.
0.14236
5. Maximum depth of flow,ft.
0.12467
6. Average depth of flow,ft.
0.03635
7. ,~ver8.gevelocity
0.22633
of
flow,fps.
8. >vetted perimeter, ft.
'~.10105-
9. Hydraulic radius, ft.
0.03471
10. Meander len~th,ft.
9.59646
11. Meander thalweg len~th,ft.
13.53346
12. Channel length, ft.
8.25000
13. Channel sinuosity
1.1632-1
14. Thalweg sinuosity
1.64042
15. Shear stross,pound/sft.
0.00511
16. Stream power,ft-lb/sec.ft.
0.00474
17. Maximum depth to width ratio
0.03183
18. Froude Number
0.20920
llftergroin
placing
0.00203
4.12500
0.28646
0.21982
0.06944
0.11248
4.26509
0.06716
10.43307
14.'76378
9.50000
1.09822
1 .55408
0.00851
0.00408
0.05329
0.07522
19. Relative r8.dius of curvature
1.19149
20. Mannings roughness
co-efficient
0.03356
.
'-,'" - ~.
1.13131
116
Table - 6 (Gontd.)
Set u:
3
Ini tial channel [-.ope: 0.00333
Discharge
0.03222 cfs
Section: 4-4
Groin projection
Groin Location
29.89%
Bend centre
Before groin
placing
After groin
placing
21. Maximum scour depth, ft.
0.24606
22. Plan area of scour,sft.
0.52030
23. Downstream length protected,ft.
1.00000
24. Upstream bank caving
0.04167
25. Scour c0TIstant,K
5.82555
26. Downstream lpngth protected/
Prnjoction
0.92308
27. Upstream bank caving/projoction
0.03846
28. DJwnstrorun len~th protected/
width
2424200
29. Maximum scour devth/width
0.08559
117
~e
Sot up : 4
Section: 1-1
-7
Initial channel
Discharge
Groin projection
Groin Position
5.07%
10% Upstream
slope:
0.00333
0.03222
cfs
from bed centre
Before groin
.placing
After groin
placing
1. SlnpG
0.00201
0.00216
2. Projection,ft.
0.14583
3. Channel width,ft.
3.50OC)O
3.75000
4. Area of cross-section,sft.
0.10764
0.20313
5. Maximum
depth of flow,ft.
0.06562
0.27887
6, Average
depth of 'flow,ft.
0.03075
0.05417
0.29933
0.15862
3.60892
4.01903
0.02983
0.05054
7. Average velocity
8. Wetted
of flow,fps.
pGrimeter, ft.
9. Hydraulic
radius, ft.
10. Me'nder
length, ft.
10.03937
10.62992
11 • Meander
thalweg
13.38583
13.81890
12. Channel
length, ft.
9.00000
8.00000
13. Channel
sinuosity
1 .11 549
1.32874
1,1. ThalwGg
sinuosity
1 .48731
1.72736
0.00374
0.00681
0.00404
0.00434
.0.01875
0.07437
0.30082
0.12010
'1 .57143
1.46667
length, ft.
1 5. ShGar stross,pound/sft.
16. Stream power,ft-lb/sec
17. I'Iaximum depth t() width
.ft.
ratio
18. Froude Number
19. Relative
radius
of curvature
20. I'Iannings r()ughness
c o-Gffici ent
0.02116
0.05893
11 8
Table - 7 (Canto.)
Set ur : 4
Section: 1-1
Initial ch9nnel slope: 0.003'13
Discharge
0.03222 cfs
Groin projection
Groin Position
5.07%
10% Upstream from bed centre
Before groin
placing
After groin
placing
21. Maximum scour depth,ft.
0.23622
22. Plan area of scour,sft.
0.25417
23. Downstream length protected,ft.-
0.41667
24. Upstream bank caving
0.45833
25. Scour constant,K
4.12570
26. mwnstream length
protected/prnjection
2.85723
27. Upstream bank caving/
projection
3.14633
28. Downstream length projected/
width
..
0.11111
29. Ma;:imum scour deoth/wiith
0.06299
119
Ta.ble - 8
Set up : 4
Section: 4-4
Initial channel slope: 0.00333
Discharge
0.03222 cfs
Groin projection
Groin position
10.42%
1CI/o Upstream from bend centre
Before groin
placing
After groin
placing
1. Slope
0.00201
0.00216
2. Projection, ft.
0.31250
3. Channel width,ft.
3.83333
3.75000
4. Area of cross-sect inn, sft.
0.11458
0.21354
5. Maximum depth of flow,ft.
0.10827
0.23950
6. AvereJ;;:e
depth of fiow, ft.
0.02989
0.05694
7. Average velocity of flow, fps.
0.28120
0.15089
8. Wetted perimeter,ft.
3.93701
").93701
9. HYdraulic radius, ft.
0.02910
10. Meander l.ength,ft.
8.0708 (
11. Meander thalweg length, ft.
11 .25984
0.05424
9.4-8819
13.38583
12. Channel length,ft.
7.00000
13. Channel sinuosity
1.15298
14. Thalweg sinuosity
1.60855
15. Shear stress,pound/sft.
0.00365
16. Stream power,ft-Ib/sec.ft.
0.00404
17. Maximum depth to width ratio
0.02824
0.06387
0.28663
0.11144
1.21739
1 .24444
0.02215
0.06495
18. Froude Number
8.00000
1.18602
1.67323
0.00731
0.00434
•
19. Relative radius of curvature
20. Mannings roughness
co-efficient
120
Table .• 8 (Contd.)
Set up : 4
Section: 4-4
Groin projection
Groin position
Initial
channel
Discharge
slcpe:
0.00333
0.03222 cfs
10.42%
Upstream from bend centre
Before groin
lifter groin
placing
placing
21 ~ Maximumscour depth,ft.
10%
0.19357
22. Plan area of scour, sft.
23. Downstream length protected,ft.
24. Upstream bank caving ..
25. Scour c0nstant,K
26. D8wnstream length
prcjection
0.32222
0.57500
0.08333
4.42259
prot8ctod/
2.40000
27. Upstream bank caving/projection
28. Downstream lenR"th protected/width_
0.15333
29i Maximumscour depth/width
0.05162
0.26666
12'i
•
Table - 9
Set
up : 5
Soction:
Initial
1-1
channel
slope:
Discharge
Groin projection
0;03222
1 ()% Upstream from bend centre
Before groin
placing
S10pe
0.00201
2. Projection,
cf,
15.28%
Groin position
1.
0.00333
ft.
After gro:;~:placing
0.00216
0.45833
3.
Channel width, ft.
4.
3.25000
3.50000
Area of cross-section,sft.
0.12326
0.30382
5. Maximumdepth of flow, ft.
0.08530
0.26247
6. Average depth of flow, ft.
0.03793
0.08681
of flow, fps.
0.26140
ft.
3.28084
0.10605
J ?1
3.60892
0.03757
0.08419
7.
Average velocity
8. Wetted p orimeter,
9. Hydraulic
fo.
radius;i't,.
Me~'nder length,
ft.
9.8425"10.43:307
11.'MGand~r",.thalweg,"1~ng:th~i:t,. ,'~"_:_.t2,:Z559.1_,_,,'-:
..,J3,L6~,{j_6'
"I. ~ . .
1'
"
'
12. Channel, length, ft. '
13. Channel sinuosity
14. Thalweg sinuosity
'? .;Shear
stross,
16.
stream
'7 .
Maximumdepth
pound/ sft.
p01~er,ft-Ib/sec.
Relative
radius
' ..09361
1 .1 5923
to width
_-
--
•.••
",.
•
••••••••
i:52012
< •• ,.
0~OG471
0.011,35
ft. '
0.00404
,.
0.00434
rn tic
0:02625
0.07499
0.23653
0.06343
1 .641 03
1 .52381
0.(;2828
0; 12407
18. Froude Number,
'9.
9.00000
, .L4F32
••••
1
9.00000
of curvature
20. Mannings roughness
co-efficient
"
,
,
I
•
.Table' 9
(Contd.)
I
Set ur : 5
Section: 1-1
Groin projection
Gro in po sition
Initjll channel slo.[: 0.00333
Discharge
0.03222 cfs
15: 28%
"
:
10%
Up8tream from bend centre
!I
11
21 • Maximum scour depth,ft.
Br;fore groin
&acing
\I
22. Plan area of scour,8ft.
'I
23. Downstream length ~rotected,ft. _
24. Upstream bank cavJg
25. Scour constant, Ki,l
After gro:Le
placing
0.20669
0.3741'1
0.18750
26. Downstream len~th protscten/
pro .iection
27. Upstream bank cavin~/
project
~
1.27273
C.40909
28. Downstream length protected/
width
0.19444
29. Ma-imum scour depth/wic1th
,.
I
0.05905
123
Table Set uI : 5
Section: 4-4
Groin projection
Groin position
10
InitiQl channel slop
Discharge
0.03222
cfs
19.87%
10%
Upptream of bend centre
Slope
1.
0.00333
2. Projection,ft.
Before groin
placing
.tuter groin
placing
0.00201
0.00216
0.64583
3. Channel width,ft.
3.75000
3.25000
4. Area of cross-section,sft.
0.11632
r.22917
5. MQximum depth of flow,ft.
0.10171
0.23622
6. Average depth of f10w,ft.
0.03102
0.07051
7,. Avera;;revelocity
0.27699
of flow,fps.
8.
Wetted perimeter. ft.
3.85499
9.
Hydraulic radius,ft.
0.03017
10., Meander lenl";th,
ft.
11.
Me ,nder thalweg length, ft.
1'2 •.
Channel length, ft,
7.87402
11 .023C
0.14060
3.36286
0.06815
7.48031
12.20472
7.00000
6.50000
13. Channel sinuosity
1 .12486
1 .1 5082
14. Thalweg sinuosity
1.57480
1 .~7765
1~. Shear stress,pound/sft.
0.00378
0.00919
16. stream
0.00404
0.00434
17. Maximum depth to width ratio
0.02712
0.07268
18. Froude Number
0.27715
0.093:31
19. Relative, radius of curvature
1 .42222
1 .64102
power, ft-Ib/sec. ft.
20. Mannings r0ughness
co-efficient
0.08122
124
Table - .10 (Contd.)
Set up : 5
Section:
Initial cnannel
Disc4erge
4-4
Groin projection
Groin position
slope: 0.00333
0.03222 cfs
: 19.87%
10% Upstream
of bend centre
Before groin
placing
21. Maximum
scour ~epth,ft.
22. Plan area of scour,sft.
23. Downstream
2<~. Upstream
length protpcted,ft._
bank caving
25. Scour constr:mt,K
26.
Downstream
projection
Downstream
w~cth
0.23622
0.43417
0.66667
{].04167
4.48096
Ipnl2:thprGtcctcl'lJ
1.03227
27. Upstream bank cavin",/
projection
28.
lStcr groin
placing
0.06452
length protecte(lj
29. Maximum scour depth/width
--------------------_._---_.-.-
0.20513
0.07268
----~----.-
.
125
Tabie - 11
Set
UD
6
:
Section:
Initial
1-1
channel
sl~pe: 0.00333
Discharge
Groin projection
Groin Position
0.03222
25%
10%
Upstream
from bend centre
Before groin
placing
1•
cfs
After groin
placin,,,:
Slope
0.00232
2. Projection,ft.
0.00231
0.81250
3. Channel width,ft.
3.91667
3.25000
4. Area of cross-section,sft.
0.09722
5. Maximum depth of flow, ft.
0.18750
C'.09514
0.23950
0, 02482
0.05769
0.33866
0.17184
3.96982
3.33005
0.02449
0.05630
9.35039
9.35039
12.7952~
12.89370
8.37500
8.50000
1 .11 646
1 .10005
1 .52779
1. 51691
1 5. Shear stress,pound/sft.
0.00355
0.00812
16. StreE\m power,ft-lb/sec.ft.
0.00466
0.00464
0.02429
0.07369
0.37882
0.12608
1.34042
1 .61538
0.01760
0.06047
6. Average
depth of flow, ft.
7. Average velocity
of flow,fps.
8. Wetted perimeter,ft.
9. Hydraulic
1O. Meander
radius,ft.
length,ft.
11 • Me ~nder thalweg
length
12. Channel
length,ft.
13. Channel
sinu0si ty
14. Thalweg
17. Maximum
ft.
sinunsity
depth to width ratio
18. Froude Number
19. Relative
radius
of curvature
20. Mannings roughness
co-efficient
126
Table - 11 (Contd.)
Set u:. : 6
Section:: 1-1
Groin projection
Groin posi tion
Initial channel
Discharge
S..LOpe:
0
0.03222
cfs
25%
10% Upstream from bend centre
Before groin
placing
21
0.00333
After groin
placing
Maximum scnur depth, ft.
0.24606
22. Plan area of scour,sft.
0.46056
23. Downstream lCl')gthprotectc:d,ft._
0.81250
24. Upstream bank ecaving
25. Scour constant,K
4.46529
26. DOlVllstreamlenath protected/
projection
1 .00000
27. Downstream len~th protected/
width
28. Maximum scour depth/width
0.20745
0.07571
127
Table - 12
Set up : 6
Section: 4-4
Initial channel slope: 0.00333
Discharge
0.03222 cfs
Groin projection
Groin position
30.13%
10% Upstream from bend centre
Before groin
placineL-_
1. Slope
0.00232
2. Projection,ft.
After groin
placing
0.00231
0.97917
3. Channel Width,ft.
3.50000
3.66667
4. Area of cross-section,sft.
0.09896
0.19097
5. Maximum depth of flow ,ft.
6. Aver'ige depth of flow,ft.
0.08530
C.20013
0.02827
0.05208
7. Average velocity OI flow,fps.
0.32559
0.16872
8. Wetted porimcntor,ft. ,
3.60892
9. Hydraulic rarlius,ft.
(S.02742
10.Melder
8.8582',
length, ft.
11. Meander thalwog lc,ngth,ft.
_
•
N
".
••
•
'.
•
:
,
_
_
•••
:_.
••
•
'.
12.00781
12. Channel length,ft.'
8.00000
13. Channol sinuosity
1.10728
14. Thrllwegsinuosity
1.50098
15. Shear stress,pound/sft.
O.P0397
16. Stream power,ft-Ib/sec.ft.
0.00466'
17. Maximum depth to width ratio
0.02437
18. Froude Number
0.34126
19. Relative radius of curvaturo
1.57143
20. JVIanningsroughness
coefficiont
F
I'
C.01975
3.77297
0.05062
9~84252
13.28740
9.50000
1.03605
1 .39867
0.00730
0.00464
0.05458
0.13029
1.50000
0.05735
128
Table - 12 (Contd.)
Set up : 6
Section: 4-4
Gro in pro ,jection
Groin position
lnitial channel slope: 0.00333
Discharge
0.03222 cfs
30.137
101, Upstream from bRnd centre
Before groin
l21.acing
,!lftergroin
placing
21. Maximum scour depth,ft.
0,24606
22. Plan area of scour,sft.
0,57528
23. Downstream length protected, ft.
0.522083
24. Upstream bank caving
25. Scour constant,K
4.76717
26. Downstream length protected/
prejection
27. Upstream bank caving/
projection
'.,,,.,.
__..
,,
... _. _.~._..,..
28. Downstream length protected/
w<ith
.
0.53191.,
,
,~
-' ..
0.16026
J,e:
29. :Maximum scour r'iepth/width.,
.
",'
0.01571
, ". c.
~ - _ ..
'.~~-' ...
"
-
•