CHAPTER 5
Drainage Basin Morphometry
5.1
Introduction
Morphometric analysis is refers as the quantitative evaluation of form characteristics
of the earth surface and any landform unit. This is the most common technique in
basin analysis, as morphometry form an ideal areal unit for interpretation and analysis
of fluvially originated landforms where they exhibits and example of open systems of
operation. The composition of the stream system of a drainage basin in expressed
quantitatively with stream order, drainage density, bifurcation ration and stream length
ratio (Horton, 1945). It incorporates quantitative study of the various components such
as, stream segments, basin length, basin parameters, basin area, altitude, volume,
slope, profiles of the land which indicates the nature of development of the basin.
This modern approach of quantitative analysis of drainage basin morphology was
given inputs by Horton (1945) the first pioneer in this field. Horton's law of stream
lengths suggested that a geometric relationship existed between the numbers of stream
segments in successive stream orders. The law of basin areas indicated that the mean
basin area of successive ordered streams formed a linear relationship when graphed.
Horton’s
laws
were
subsequently
modified
and
developed
by
several
geomorphologist, most notably by Strahler (1952, 1957, 1958, and 1964), Schumm
(1956), Morisawa (1957, 1958), Scheidegger (1965), Shreve (1967), Gregory (1966,
1968), Gregory and Walling (1973). Subsequently a number of books by Bloom
(2002), Keller and Pinter (1996) have further propagate the Morphometric analysis.
Stream profile analysis and stream gradient index by Hack (1973) is another milestone
in morphometric analysis. Many workers have used the principles developed by these
pioneers to quantitatively study the drainage basin as a tool for landscape analysis
(Sharma, 1987, Raj et. al., 1999, Awasthi and Prakash, 2001, Phukon, 2001, SinhaRoy 2002).
115 Quantitative measurements of morphometry used as a reconnaissance tools to make
inferences about particular characteristic of an area viz., tectonic activity. Some
geomorphic indices like hypsometric integral, drainage basin asymmetry, stream
length gradient index, mountain front sinuosity etch are used a measure of active
tectonics (Keller and Pinter, 1996; Sinha-Roy, 2002). Landforms are created via
erosional and depositional processes, the geometry of which is controlled by the
processes that shape them. Morphometric analyses require measurement of linear
features, gradient of channel network and contributing ground slopes of the drainage
basin (Nautiyal, 1994). The morphometric analysis for individual sub basins has been
achieved through measurements of linear, aerial and relief aspect of the basin and
slope contribution (Nag and Chakraborty, 2003).
The basin geomorphic characteristics have long been believed to be important indices
of surface processes. These parameters have been used in various studies of
geomorphology and surface-water hydrology, such as flood characteristics, sediment
yield, and evolution of basin morphology (Jolly, 1982; Ogunkoya et al., 1984;
Aryadike and Phil-Eze, 1989; Breinlinger et al., 1993; Jensen, 1991). By including
basin characteristics such as elevation and main channel gradient, predictions of
stream discharge were substantially improved in comparison to using only drainage
area and precipitation (McArthur and Hope, 1993). More recently, terrain
characterization became an important part in modelling surface processes (Nogami,
1995). The detailed analysis of morphometric and morphological character indicate
the role of the neotectonics in shaping the drainage basin (Raj et.al., 1999).
Geographical Information system (GIS) and Remote sensing techniques using
satellite images are used as a convenient tool for Morphometric analysis. Many
workers have carried out morphometric analysis using these new techniques. Digital
Elevation Model (DEM) and Shuttle Radar Topography Mission (SRTM) widely
used in drainage basin analysis. Srivastava, 1997, Nag, 1998, Duarah et al., 2011,
carried out morphometric analysis, while Nag and Chakraborty (2003) deciphered the
influence of rock types and structures in the development of drainage network in hard
rock area.
116 As the main objectives of this work was to discover holistic stream properties from the
measurement of various stream attributes, detailed morphometric analysis is carried
out for the 41 fifth-order drainage sub-basins of Jia Bharali River catchment and
discusses their feature and characteristic and also attempt to find out the stages of
geomorphic development with the help of different morphometric parameter viz.,
streams order, streams number, streams length, mean streams length, bifurcation
ratios, elongation factor, circularity index, shape factor, drainage density, stream
frequency, texture ratio, relief ratio, length of overland flow, constant channel
maintenance, infiltration number, hypsometric curve and longitudinal profiles.
Morphological Studies of rivers are very important to study the behaviour of a river,
its aggradations/degradation, shifting of the river course, erosion of river bank etc. and
to plan remedial measure for erosion and other related problems. Most of the streams
appear to be in conformity with the geological and structural setup of the area.
For detail morphometric analysis of the drainage within Jia Bharali River catchment at
first the fifth order sub basins are delineated from the available toposheet after
assigning ‘stream order’ to all the segments following Horton's (1945) method
modified by Strahler’s (1952). In general the entire fifth order sub basins are selected
for the morphometric analysis in following heads:
•
•
•
Linear Aspects
Areal Aspects
Relief Aspects
:
:
:
one dimension
two dimensions
three dimensions
The prime objective of morphometric analysis is to find out the drainage characteristic
to explain the overall evaluation of the basin. Morphometric analysis comprises a
series of sequential steps. The drainage layer has been converted to digital format
through on-screen digitization from available Survey of India (SoI) topographic maps
using GIS software Arc-Info 9.1, in the scale of 1:50000 and the attributes were
assigned to create the digital database. Toposheet for the total basin catchment is not
available as the area has sensitive political controversy. Some part of the basin fall in
the international boundary of Bhutan and China. All measurements were directly
computed from the vector data that extracted from the topographic maps. The entire
drainage segments were digitized as lines separately for each order (Strahler 1952).
117 Fifth order drainage sub-basins are delineated following surface water divide.
Topological polygons were created and the attribute Table generated thus yielded the
basinal areas.
In absence of the Survey of India topographic maps for the
northernmost part of the Jia Bharali basin, the surface water divide and was delineated
with the help of satellite imagery and SRTM DEM. Major sub basin boundaries were
also delineated following this method. Thus 41 fifth-order drainage basins were used
as a statistical sample representative for the entire drainage system to compute the
morphometric parameters analysis (Figure 5.1, Table 5.1).
Figure 5.1: Delineated fifth order sub-basins for morphometric analysis
The morphometric parameters for each basin were directly computed from the vector
data extracted from the topographic maps (basic parameters). The data in the first
category includes maximum order of the streams, number of streams in each order,
length, area, perimeter, relief for each of the basins. Those of the second category are
118 the bifurcation ratios, elongation factor, circularity index, shape factor, drainage
density, stream frequency, texture ratio, relief ratio, length of overland flow, constant
channel maintenance and infiltration number.
Linear, aerial and relief aspects of the basin were computed in GIS environment
followed by simple linear regression analysis to see the mutual dependency of some
variables viz., i) stream order vs. stream number, ii) stream order vs. stream length
and iii) stream order vs. Mean stream length. For hypsometric analysis the elevation
contour are generated in ArcInfo 9.1 from the SRTM DEM. The contour layer and
the basin boundary are merged in a single layer and converted into polygon. From the
attribute Table of this polygon layer the area the between two contours within the
basin are noted. Maximum height (H) is the difference between the maximum
elevation and the minimum elevation and, which are calculated by extrapolation.
Mean elevation for each basin also calculated by dividing the sum of frequency of
each pixel elevation by the total number of pixel in the basin. Details of the
morphometric parameters are tabulated followed by analysis of the parameters
through bivariate plots.
119 Table 5.1:
Basin
Index
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
Fifth order sub basin index and basin name used in the study
Basin Name
Dipota Nadi
Jorasar Nadi
Mansari Nadi
Dibru Nadi
Khari Dikrai Nadi
Upar Dikrai Nadi
Daigurang Nadi
Khaina Nadi
Lengtey Nadi
Diju Nadi
Pakke River
Tributary of Pakke River
Tributary of Kameng River
Pasa Nadi
Pani Nadi
Papu River
Chakrasong Nadi
Tributary of Pacha River
Pacha River
Lengpla Nadi
Phuchao Nadi
Kade Nala
Pakoti Nadi
Hoda Nadi
Huduri Nadi
Kaun or Hukubu Nala
Gayang River
Ki Nala
Miao Nadi
Upstream of Dinang Bru
Dibri Bru
Difya River
Khenda Nadi
Taamchin RI (Sashi Chu)
Meni Nadi
Nimsinggoto River
Dublo Kho
Tribtary of Tenga River
Dogong Kho
Sessa Nadi
Tipi Nala
120 Basin
Basin Area
Perimeter (km)
(Sq km)
85
255
64
91
78
165
36
59
46
82
41
75
33
37
41
71
37
71
36
45
135
328
22
28
23
24
58
118
32
49
43
95
39
64
21
22
35
65
17
16
29
44
28
42
35
75
23
30
29
36
35
48
47
102
29
37
23
22
33
52
34
51
24
28
20
22
38
71
25
34
27
38
71
163
41
72
28
37
31
44
61
103
All the fifth order sub basins are grouped into three divisions. The group of the
completed fifth order drainage sub basin (Figure 5.2) are based on the lithotectonic
setup of the area. The basins in Zone-I are predominantly within the alluvium south of
HFT. Zone-II is mainly characterised by the folded Cenozoic/Gondwana sequence
with pertinacious E-W structural lineament spreading into both side of MBT but
within the HFT and the Pronounced NE-SW lineament. The Zone-III is characterised
by dissected crystalline terrain.
Figure 5.2:
5.2
Showing the assign three Zone for the drainage basin
Linear aspects
The drainage network transport water and the sediments of a basin through a single
outlet, which is marked as the maximum order of the basin and conventionally the
highest order stream available in the basin considered as the order of the basin. The
size of rivers and basins varies greatly with the order of the basin. Ordering of streams
is the first stage of basin analysis.
121 Stream Order (U)
There are four different system of ordering streams that are available Gravelius
(1914), Horton (1945), Strahler (1952) and Schideggar (1970). Strahler’s system,
which is a slightly modified of Hortons system, has been followed because of its
simplicity. Where the smallest, unbranched fingertip streams are designated as 1st
order, the confluence of two 1st order channels give a channel segments of 2nd order,
two 2nd order streams join to form a segment of 3rd order and so on. When two
channel of different order join then the higher order is maintained. The trunk stream is
the stream segment of highest order.
The total Jia Bharali drainage basin boundary and major river system are delineated
from the satellite imagery and SRTM. It is found that Jia Bharali River is an 8th order
stream. The analyses of morphometric parameters are carried out for the entire 41 fifth
order basin.
Stream Number (Nu)
The total number of stream segments present in each order is the stream number (Nu).
Nu is number of streams of order u. In this present study all the 5th basin are counted
and tabulated for the analysis from the attribute Table of the vector layer (appendixIII). The total number of stream segments is found to decrease as the stream order
increases in all the sub basins. The study reveals that the development of 1st order
streams is maximum in the Himalayan dissected zones and minimum in the alluvial
plains (Table. 5.2). Similarly the numbers of 2nd and 3rd order streams are gradually
high from alluvial to highly dissected hills from south to north.
Stream Length (Lu)
The total length of individual stream segments of each order is the stream length of
that order. Stream length measures the average (or mean) length of a stream in each
orders, and is calculated by dividing the total length of all streams in a particular order
by the number of streams in that order. The stream length in each order increases
exponentially with increasing stream order.
122 From the overall drainage of the study area shows the frequency of the drainage
development is less in the alluvial part (0.7 km-2) and high above the MBT (4.5 km-2)
whereas the overall drainage frequency is 3.8 km-2. It reflects the frequency of the
drainage is high in the upper part of MBT. The drainage density also shows that the
development of drainage is higher in the upper part of MBT. The alluvial part has a
drainage density of ~1 km-1 where as the area above the MBT is 2.9 km-1. The overall
drainage density of the area is 2.6 km-1. It clearly reflects that the drainage
development in the upper part of the MBT is high and the area is highly dissected.
Mean Stream Length (Lū)
Mean stream length of a stream channel segment of order ‘u’ is a dimensional
property revealing the characteristic size of components of a drainage network and its
contributing basin surface (Strahler, 1964). The lengths of stream segments of up to
5th order are measured and the total length as well as Mean Stream Length (Lū) of
each order is computed (appendix-III). The mean stream lengths of stream increase
with the increase of the order. But in some basin shows opposite relation, higher order
stream has a small mean length. In Zone-I, Basin 2, in Zone-II, Basin 4, 12, 13, 16 and
in Zone-III, Basin 18, 24, 29, 33, 35 the length of 5th orders stream is extremely short.
These basin shows variable lithology with asymmetry in nature and these basins are
found along the major structural lineament. The basins shows high hypsometric
integral value and high relative upliftment, reveals the tectonic control on these sub
basins.
In order to find the relation between basin area and the total stream length for
respective sub basins a regression line is constructed using a double log graph. It is
observed that the drainage area bears a power function relationship with stream length
(Figure 5.3)
123 Figure 5.3
Log-Log plot of Basin Area (Au) vs. Total Stream Length (Lu) shows
conformable relation of basin area and total stream length.
Stream Length Ratio (RL)
The Length Ratio (RL), which is the ratio of the mean length of the stream of a given
order (Lu1) to the mean length of the streams of the next lower order (Lu-1), is then
calculated for each pair of the orders. Length ratio is for 1st-2nd and 2nd -3rd order of
the alluvial plain basin are higher than the basin of other two zones. Elongated basins
(Basin index 7, 14, 37, 41) shows high length ration (up to 14.1 in case of Basin41) in
the higher order where as the basin (Basin index 12, 13, 16, 29, 35) with
comparatively high circularity ratio shows the low length ratio (<1). The variation in
length ratio, attributed to variation in slope of topography indicate youth stage of
geomorphic development in the streams of the study area (Singh and Singh, 1997,
Vittala et al., 2004)
124 Table 5.2: Summary of drainage basin parameters in the study area
Division
Order
u
South of HFT
HFT-MBT
MBT-MCT
Above MCT
In total (available
drainage)
1
2
3
4
5
1
2
3
4
5
1
2
3
4
5
1
2
3
4
5
1
2
3
4
5
Stream
Number
Nu
556
134
33
9
4
∑Nu=736
3346
706
149
44
12
∑Nu=4257
15624
3418
762
172
30
∑Nu=20006
220
54
12
2
0
∑Nu=287
19602
4256
939
212
41
∑Nu=25050
Bifurcation
Ratio
4.1
4.1
3.7
2.3
4.7
4.7
3.4
3.7
4.6
4.5
4.4
5.7
4.1
4.5
6.0
4.6
4.5
4.4
5.2
Mean Bifurcation
Ratio
3.5
4.1
4.8
4.8
4.7
Stream
Length (km)
Lu
479.5
213.5
162.5
81.9
80.4
∑Lu=1017.7
1995.8
690.9
307.3
176.8
162.7
∑Lu=3333.5
8763.2
2438.2
1202.1
595.6
269.8
∑Lu=13268.9
129.7
32.2
13.1
4.5
∑Lu=179.5
11261.5
3276.3
1629.2
802.1
402.6
∑Lu=17371.7
125 Mean Stream
Length (km)
Lū
0.9
1.6
4.9
9.1
20.1
Area
(sq km)
Au
1027.0
Drainage
Density (km-1)
Dd
1.0
Drainage
Frequency (km-2)
Df
0.7
0.6
1.0
2.1
4.0
13.6
1150.4
2.9
3.7
0.6
0.7
1.6
3.5
9.0
4426.1
3.0
4.5
0.6
0.6
1.1
2.3
50.4
3.6
5.7
0.6
0.8
1.7
3.8
9.8
6653.9
2.6
3.8
Table 5.3: Mean Stream Length for all the order for entire 41 fifth order basin
Order
Basin
Index
1
2
3
4
5
Order
Basin
Index
1
2
3
4
5
1
0.7
1.3
5.2
6.4
29.9
2
0.8
1.3
3.8
13.3
1.0
3
0.9
1.4
4.1
9.9
33.9
4
0.5
0.9
2.4
7.3
0.6
5
0.7
1.2
2.0
7.0
11.2
21
0.5
0.8
1.8
3.5
3.1
22
0.6
0.8
1.6
1.5
6.8
23
0.6
0.7
1.3
3.0
10.1
24
0.5
0.7
1.2
3.9
1.0
25
0.5
0.6
1.2
4.3
4.9
6
0.6
1.2
2.5
4.9
6.7
26
0.5
0.9
1.1
4.0
7.9
7
0.6
0.7
1.7
1.1
12.1
8
0.5
0.7
1.5
2.9
10.5
27
0.5
0.6
2.1
4.3
8.1
28
0.5
0.5
1.2
2.9
8.0
Mean Stream Length
9
10
11
12
0.5
0.6
0.6
0.5
0.9
0.7
0.8
0.7
1.7
1.5
1.4
1.4
1.1
4.4
4.5
3.0
12.0
7.8 65.0
2.0
Mean Stream Length
29 30
31 32
0.5 0.5
0.6 0.5
0.3 0.6
0.6 0.3
1.3 1.1
1.1 1.0
3.9 2.8
3.1 1.9
1.9 7.5
8.5 6.2
13
0.6
0.6
1.0
3.1
0.8
33
0.6
0.6
0.9
2.3
1.3
14
0.5
0.6
1.9
2.7
14.8
34
0.6
0.9
1.4
2.5
10.1
15
0.6
0.7
1.2
2.0
7.9
35
0.6
0.5
1.0
4.3
1.2
16
0.7
1.6
3.0
6.8
0.9
36
0.5
0.7
1.5
1.5
5.0
17
0.5
0.7
1.4
4.8
5.4
37
0.5
0.8
1.4
3.3
24.9
38
0.6
0.8
1.6
4.8
7.1
18
0.6
0.7
1.5
1.5
0.3
39
0.6
0.8
1.6
1.5
6.5
19
0.6
0.7
2.7
2.5
4.7
20
0.5
0.6
1.0
0.8
2.7
40
0.5
0.7
0.8
6.1
5.2
41
0.6
0.8
2.0
2.0
29.0
19
1.1
4.0
0.9
1.9
20
1.3
1.5
0.8
3.6
40
1.3
1.1
7.6
0.9
41
1.5
2.4
1.0
14.4
Table 5.4: Stream Length Ratio for different order of the entire 41 fifth order basin
Order Basin
Ratio Index
2nd/1st
3rd/2nd
4th/3rd
5th/4th
Order Basin
Ratio Index
2nd/1st
3rd/2nd
4th/3rd
5th/4th
1
1.9
4.0
1.2
4.7
2
1.6
3.0
3.5
0.1
3
1.6
2.9
2.4
3.4
4
1.7
2.6
3.1
0.1
5
1.7
1.6
3.5
1.6
21
1.4
2.4
1.9
0.9
22
1.4
2.0
1.0
4.5
23
1.2
1.9
2.3
3.4
24
1.4
1.7
3.4
0.3
25
1.1
2.0
3.5
1.1
6
2.1
2.2
1.9
1.4
26
1.7
1.1
3.8
2.0
7
1.2
2.3
0.7
10.6
8
1.4
2.0
2.0
3.6
27
1.2
3.4
2.1
1.9
28
0.9
2.5
2.5
2.7
Length Ratio (RL)
9
10
11
12
1.9
1.2
1.4
1.4
1.8
2.1
1.8
2.1
0.6
3.0
3.3
2.1
11.4
1.8 14.4
0.7
Length Ratio (RL)
29 30
31 32
0.7 1.3
1.1 0.5
3.9 1.8
1.7 3.8
3.1 2.7
2.9 1.9
0.5 2.6
2.7 3.2
126 13
1.2
1.6
3.0
0.3
33
1.0
1.5
2.5
0.6
14
1.2
3.0
1.4
5.6
34
1.4
1.6
1.8
4.1
15
1.1
1.7
1.7
3.9
35
0.8
2.0
4.3
0.3
36
1.2
2.3
1.0
3.4
16
2.4
1.9
2.3
0.1
17
1.2
2.1
3.4
1.1
37
1.4
1.8
2.3
7.6
38
1.3
2.0
3.1
1.5
18
1.1
2.2
1.0
0.2
39
1.3
2.1
0.9
4.3
Bifurcation Ratio (Rb)
The bifurcation ratio is the ratio between the number of streams in one order and in the
next. It is calculated by dividing the number of streams in the lower by the number in
the higher of the two orders; the bifurcation ration of large basins is generally the
average of the bifurcation rations of the stream orders within it.
The bifurcation ratio of the basin of alluvial region is comparatively low than the
Himalayan zone. The bifurcation ratio is range of 3-5 in case of overall drainage system
of the basin. It is seen that the bifurcation ratio of 2nd and 3rd order stream is higher
than the other ratio (Appendix-III and Table 5.2). The sub basins belongs to the Zone-I
shows the bifurcation ratio of 2-4 of different order whereas the mean bifurcation ratio
in between 3.3-4.2. Similarly the Zone-II basins of eastern part of the Kameng River
having origin along the MBT with N-S directional flow and basins origin in the extreme
eastern boundary with a E-W flow have a mean bifurcation ratio of 3-4.6.
The
bifurcation ratio of the lower order shows a higher value. This reflects the high
dissection in the upland area. The sub basin 11 and 14 shows a high bifurcation ratio 48 in the higher order. The sub basin 11, Pakke river has an elongated course, it origin
near the eastern margin of the basin and the trunk channel flows along the major
structural control of MBT in the Gondwana sequence in E-W direction. It turns south in
through a transverse lineament, flow across the MBT and it again turns towards east
upto the MBT. It again turns to south along N-S transverse lineament and through
Siwalik it confluence with Dibru N and flow as Bor Dikrai River up to Jia Bharali in the
alluvium. The pattern of the river itself reflects the structural disturbance of the area.
The higher Bifurcation ratio suggests that the area is tectonically active (Som et.al.,
1998).
In case of Pasa Nadi (basin index 14) shows higher bifurcation ratio of 6, this indicates
the structural control. In longitudinal profile also it is also seen that in the river course
there is lithological and structural control. And the drainage between the MBT and
MCT have comparatively higher bifurcation ratio. As per the Horton (1945) bifurcation
ratio having a less value about 2 to 3 is of flat region. The basins of alluvial plain the
ratio higher order is approximately 2 it reflects that the lower part of the basin is flat.
The mean bifurcation ratio is 3.8. Other hand the ration of the lower order is high and as
per Horton these streams or of highly dissected drainage basins.
127 The Bifurcation Ratio is of fundamental importance in drainage basin analysis as it is
the foremost parameter to link the hydrological regime of a watershed under topological
and climatic conditions (Raj et. al., 1999). It helps to have an idea about the shape of
the basin as well as in deciphering the run off behavior. The bifurcation ratio will not be
exactly same from one order to the next order because of possibility of the changes in
the watershed geometry and lithology but will tend to be consistent throughout the
series. From the Figure 5.4- i,ii,iii, it is clear that the Zone-III basins have ruggedness
topography as it shows a high variation in the bifurcation ratio. The Zone-II basins are
also comparatively highly rugged topography than the alluvial part basins. The area
under the Zone-II and Zone-III are moderately and highly dissected area and the
drainage development is high.
Mean Bifurcation Ratio ( Rb ) is calculated as the Arithmetic Mean Bifurcation Ratio
and the result is tabulated corresponding to Sub-order basins as shown in the Table
appendix-III. Using Strahler's (1957) method of taking into consideration of actual
number of streams that are involved in the ratio, Mean Bifurcation Ratio of different
sub-basins was calculated. The mean bifurcation ratio is in between 3-5.9. The basin
having index 18 has the lower bifurcation ratio of 3 and the basin 11 has the higher
bifurcation ratio of 5.9. The higher bifurcation ratio indicates there may be some
structural distortion in that basin area. The overall plotting of the mean bifurcation ratio
against the basin area it is seen that higher is the bifurcation ratio as the basin area
increases.
128 a b
c
Figure 5.4: a,b,c, are the plotting of bifurcation ratio and stream order of different basin in the Zone-I, Zone-II, Zone-III
a b Figure 5.5: a. shows the variation of mean bifurcation ratio. B. shows the trend of mean bifurcation ratio against basin area
129 Basin length (Lb):
Basin length is the longest dimension of a basin to its principal drainage channel. Sub
basin having index 1, 11 has the longest basin length of 33.9 km and 32.5 km
accordingly and the sub basin 20 has the shortest basin length of 5.5km. Basin length
and the basin area of the alluvial river are maximum and in the dissected hill it is
minimum. Basin lengths for the entire basin are tabulated in the given appendix-III.
Regression Analysis
Graphical presentation of i) the stream order and the stream number ii) the stream
order and the stream length iii) the stream order and the mean stream length is
prepared in a semi-log plot as suggested by Strahler (1957). For this regression
analysis number of streams (Nu) of each order and their length (Lu) are noted from
the attribute Table. All these aspects are then entered in an excel sheet and then the
bifurcation ratio (Rb) is calculated. For graphical plot of Stream order Vs Stream
number and Stream order Vs Stream Length we used the Regression Equation, which
is
y= a + bx
(1)
Where ‘b’ is the co-efficient of the Regression equation, which can be calculated from
the following formula –
ΣxΣy
n
b=
( Σx ) 2
Σx 2 −
n
Σxy −
Again the value of ‘a’ can be calculated from
a = y − bx
Where,
y =Mean of y
x = Mean of x
By plotting the values of ‘x’, ‘a’ and ‘b’ in the regression equation (1), we get the
value of ‘y’ for corresponding stream number and stream length. Plotting the antilog
values of ‘y’ in the Y axis in logarithmic scale against ‘x’ value (order) in the X axis
in arithmetic scale, the three necessary bivariate plots are made.
130 Stream order vs. the stream number
Graphical presentation (Figure 5.6, 5.7 and 5.8) of the total stream length against the
stream order can also be prepared in a semi-log plot as suggested by Strahler (1957).
It is observed that the number of stream segment increases with decreasing stream
order in the entire sub basins i.e. negative regression relation.
Figure 5.6
Stream order Vs Stream number (-ve corrlation) for the Zone-I
Figure 5.7
Stream order Vs Stream number (-ve corrlation) for the Zone-II
Figure 5.8
Stream order Vs Stream number (-ve corrlation) for the Zone-III
131 Table 5.5
Showing the Regression equation for Stream order vs. Stream Number
Basin
Index
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
Regression
Basin
Equation
Index
y=3.07-0.62x
21
y=2.42-0.51x
22
y=2.77-0.57x
23
y=2.81-0.60x
24
y=2.83-0.60x
25
y=2.77-0.57x
26
y=2.56-0.54x
27
y=2.94-0.59x
28
y=2.98-0.60x
29
y=2.72-0.58x
30
y=3.89-0.76x
31
y=2.49-0.53x
32
y=2.28-0.48x
33
y=3.20-0.62x
34
y=2.82-0.58x
35
y=2.83-0.61x
36
y=2.87-0.59x
37
y=2.18-0.46x
38
y=2.80-0.57x
39
y=2.18-0.46x
40
41
Regression
Equation
y=2.67-0.56x
y=2.57-0.54x
y=3.07-0.61x
y=2.51-0.53x
y=2.67-0.56x
y=2.78-0.58x
y=3.22-0.65x
y=2.71-0.57x
y=2.51-0.53x
y=2.99-0.59x
y=2.90-0.60x
y=2.65-0.54x
y=2.33-0.49x
y=2.89-0.59x
y=2.72-0.57x
y=2.70-0.55x
y=3.51-0.68x
y=2.96-0.60x
y=2.59-0.55x
y=2.74-0.58x
y=3.13-0.65x
Stream order vs. the stream length
Generally, the total length of stream segments decreases with stream order. Graphical
representation of the total stream length against stream order was also prepared in a
semi-log plot as suggested by Strahler (1957). The general logarithms of the number
of stream of a given order, when plotted against the order, the points lie on a straight
line (Horton, 1945). Bivariate plot (Figure 5.9, 5.10 and 5.11) between stream order
and total stream length shows negative exponential functions, indicating that the total
stream length decreases with increase in stream order indicating that development of
drainage is higher for the lower order.
132 Figure 5.9: Stream order Vs Stream Length (-ve corrlation) for the Zone-I
Figure 5.10
Stream order Vs Stream Length (-ve corrlation) for the Zone-II
Figure 5.11
Stream order Vs Stream Length (-ve corrlation) for the Zone-III
133 Table 5.6
Showing the Regression equation for Stream order vs. Stream length
Basin
Index
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
Regression
Equation
y=4.68-0.96x
y=2.37-0.38x
y=4.51-0.93x
y=2.29-0.38x
y=3.88-0.81x
y=3.52-0.71x
y=3.54-0.80x
y=3.76-0.78x
y=3.97-0.86x
y=3.39-0.71x
y=5.58-1.17x
y=2.47-0.49x
y=1.83-0.33x
y=4.20-0.86x
y=3.55-0.76x
y=2.75-0.50x
y=3.33-0.67x
y=1.31-0.21x
y=3.34-0.68x
y=2.32-0.52x
Basin
Index
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
Regression
Equation
y=2.93-0.59x
y=3.27-0.72x
y=3.87-0.80x
y=2.12-0.39x
y=3.05-0.62x
y=3.48-0.74x
y=3.89-0.78x
y=3.28-0.70x
y=2.30-0.45x
y=3.54-0.72x
y=3.58-0.76x
y=2.95-0.63x
y=2.13-0.42x
y=3.78-0.80x
y=2.41-0.45x
y=3.18-0.67x
y=4.75-0.98x
y=3.63-0.74x
y=3.25-0.71x
y=3.15-0.65x
y=4.52-1.00x
Stream order and the Mean stream length
The values of mean stream length are plotted against respective stream order (Figure
5.12, 5.13, 5.14). These shows the positive relationship between mean stream length
and the stream order for each drainage basin. Sub-basin with index 18 shows a
relationship that reveals more or less a straight line regression of negative relation.
Again in some basin it is observed an exception where the mean stream length of
fourth order is much higher than that of the fifth order (basin index 2, 4, 12, 13, 16,
18, 24, 29 33, 35). Deviation from its general behaviour may suggest that the terrain is
characterized by high relief and/or moderately steep slopes, underlain the various
lithology and probable uplift across the basin (Singh and Singh 1997, Vittala et al.,
2004).
134 Figure 5.12
Mean stream length vs. Stream order plotting of Zone-I
Figure5.13
Mean stream length vs. Stream order plotting of Zone-II
Figure 5.14
Mean stream length vs. Stream order plotting Zone-III
135 Table 5.7
Showing the Regression equation for Stream order vs. Mean Stream
Length
Basin
Index
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
Regression
Equation
y= -0.61+0.40x
y= -0.03+0.12x
y= -0.56+0.40x
y= -0.15+0.10x
y= -0.51+0.31x
y= -0.49+0.28x
y= -0.64+0.28x
y= -0.71+0.32x
y= -0.63+0.28x
y= -0.67+0.31x
y= -1.03+0.49x
y= -0.46+0.19x
y= -0.31+0.10x
y= -0.77+0.35x
y= -0.62+0.27x
y= -0.02+0.09x
y= -0.64+0.29x
y= -0.02-0.03x
y= -0.48+0.23x
y= -0.52+0.16x
Basin
Index
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
Regression
Equation
y= -0.47+0.22x
y= -0.55+0.24x
y= -0.70+0.31x
y= -0.38+0.14x
y= - 0.65+0.28x
y= -0.64+0.30x
y= -0.69+0.32x
y= -0.78+0.31x
y= -0.64+0.22x
y= -0.76+0.31x
y= -0.71+0.30x
y= -0.89+0.31x
y= -0.37+0.13x
y= -0.62+0.29x
y= -0.44+0.16x
y= -0.56+0.23x
y= -0.86+0.40x
y= -0.61+0.29x
y= -0.56+0.24x
y= -0.67+0.29x
y= -0.80+0.38x
5.3
Areal Aspect
The areal aspect is the two dimensional properties of a basin. It is possible to delineate
the area of the basin which contributes water to each stream segment. The watershed
can be traced from where the stream has its confluence with the higher order stream
along hillcrests to pass upslope of the source and return to the junction. This line
separates slopes which feed water towards the streams from those which drain in to
other streams.
The information of hydrologic importance on fluvial morphometry is derived by the
relationship of stream discharge to the area of watershed. The planimetric parameters
directly affect the size of the storm hydrograph and magnitudes of peck and mean
runoff is the basin area. The maximum flood discharge per unit area is inversely
related to the size of the basin (More, 1967)
136 Drainage Area (Au)
The entire area drained by a stream or system of streams such that all streams flow
originating in the area is discharged through a single outlet is termed as the Drainage
Area. Drainage area measures the average drainage area of streams in each order; it
increases exponentially with increasing order.
The total catchment area of Jia Bharali as well as for the 41 fifth order basin was
computed from the topological polygon that are created by delineation basin from the
toposheet following the surface water divide in ArcInfo9.1 The basin with index 1,
i.e., Diputa River in Zone-I has a 255 sq km of basin area, Pakke River, with basin
index 11, has the highest basin area of 328 sq km in Zone-II, which is the biggest
basin among the 41 basin. In Zone-III, Dublo kho, basin index 37 has the highest
basin area of 163 sq km.
Relation between Basin area and Basin length
It is seen area of the basins of alluvial area are maximum than that of other structural
or transitional piedmont zone. In general the basin area and the basin length both are
proportional and they shows almost +ve relation. This reflects that basin area is
maximum when the basin length has a high value.
Figure 5.15: Showing the relationship between Basin Area and Basin Length
137 Drainage Density (Dd)
Drainage density has long been recognised as topographic characteristic of
fundamental significance. This arise from that fact that drainage density is sensitive
parameter which in many ways provides the link between the form attributes of the
basin and the processes operating along stream course (Gregory and Welling, 1973).
It reflects the landuse and affects infiltration and the basin response time between
precipitation and discharge. It is also of geomorphological interest particularly for the
development of slopes. Drainage basin with high Dd indicates that a large proportion
of the precipitation runs off. On the other hand, a low drainage density indicates the
most rainfall infiltrates the ground and few channels are required to carry the runoff
(Roger, 1971). Dd is considered to be an important index; it is expresses as the ratio
of the total sum of all channel segments within a basin to the basin area i.e., the length
of streams per unit of drainage density. It is a dimension inverse of length (Horton,
1932).
Dd is a measure of the texture of the network, and indicates the balance between the
erosive power of overland flow and the resistance of surface soils and rocks. The
factors affecting drainage density include geology and density of vegetation. The
vegetation density influenced drainage density by binding the surface layer and slows
down the rate of overland flow, and stores some of the water for short periods of time.
The effect of lithology on drainage density is marked. Permeable rocks with a high
infiltration rate reduce overland flow, and consequently drainage density is low.
The drainage density is found to increase from south to north of the basin (Figure
5.16). In the south of HFT the drainage density is low about 1.0 km −1 (Table 5.2).
Again it increases to about 2.9 km −1 between HFT and MBT followed by 3.0 km −1 in
between MBT and MCT. And the highest value of 3.6 km −1 attain in the area north of
MCT. The drainage density for individual basin also shows conformable relation. The
sub basin having index 1, Diputa Nadi has the lower density of 1.7km −1 in the alluvial
part. The Basin no.35, Meni Nadi, tributary of Bichom river north of MBT shows the
higher density of about 3.9 km −1 (Table 5.8). As per the zonation of basins, in this
study on the basis of lithotectonic setup of the area, it is observed that the basins of
alluvial part of Zone-I shows low drainage density (1.7-2.0 km −1 ) as this area has a
138 high permeability. The basins of Zone-II, shows comparatively higher value (2.7-3.7
km −1 ). In the piedmont zone basins shows moderate drainage density. The
precipitation in this area is very high whereas this area exhibit high vegetation also.
From the Table 5.2 and the Table 5.8 it is observed that the Dd north of MBT is 3.0
km −1 confined with Bomdila Group of rock. The sub basins in the western part of the
Jia Bharali catchment shows comparatively high drainage density (2.9-3.9 km −1 ) than
the eastern part (2.3-3.3 km −1 ), which suggest the western part is highly dissected
with a impermeable but erodible lithology.
Figure 5.16
Drainage density map of the study area. Drainage density increases
from south to north with higher value in the western part of the basin.
139 Drainage (Stream) Frequency (Fs)
Drainage frequency may be directly related to the lithological characteristics. The
number of stream segments per unit area is termed Stream Frequency or Channel
Frequency or Drainage Frequency (Fs) Horton (1945). Table 5.2 reflects the total
drainage frequency of the basins is 3.8 km-2 and the drainage frequency increase from
south to north. In the alluvial part, south of HFT is 0.7 km-2 and increase abruptly 3.7
km-2 in between HFT and MBT again north of MBT in 4.5 km-2.
The drainage frequency of the entire sub basin ranges from 1.5- 7.4 km-2. Sub basin
having index 32 Difya River has the high stream frequency and the sub basin of
alluvial has the low stream frequency (1.5 km-2). The basins of the structural hills
have higher stream frequency, drainage density while the basins of alluvial has
minimum. These higher values indicate that the area is occupied by Siwaliks in the
lower Himalayan part and the western part by the Bomdila Group of rock. Like the
drainage density, stream frequency is a similar measure of stream network of a
drainage basin. Table 5.9 shows close correlation between drainage frequencies with
drainage density indicating the increase in stream population with respect to increase
in drainage density. To evaluate the relationship between drainage density and stream
frequency, a log-log plot of drainage density vs. stream frequency is prepared. The
regression line indicates the existence of direct relationship between the two
parameters (Figure 5.17).
Figure 5.17
Relation between Drainage density and stream frequency showing the
increase of drainage frequency with drainage density
140 Drainage Texture (Rt)
Horton (1945) defined drainage texture is the total number of stream segments of all
order in a basin per perimeter of the basin. It is important to geomorphology which
means that the relative spacing of drainage lines. Drainage texture is on the
underlying lithology, infiltration capacity and relief aspect of the terrain. Smith (1950)
has classified drainage texture into 5 different textures i.e., very coarse (<2), coarse (2
to 4), moderate (4 to 6), fine (6 to 8) and very fine (>8).
The drainage texture of entire 41 sub basins are of coarse to very fine. Alluvial basins
show very coarse to coarse drainage texture and other basins of Himalayan part shows
moderate to very fine texture. Basin north of MBT and western part of Kameng (37,
35, 32, 30, 27, and 23) shows very fine texture (8-11) with higher infiltration number
(14.8-18.3) reflects high drainage development.
More is the texture more will be dissection and leads more erosion. Sub basins in the
eastern part of Jia Bharali shows moderate to fine texture (except basin having index
11 with drainage texture 10) and the western part fine to very fine texture.
141 Table 5.8:
Basin
Index
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
Computed Drainage density, frequency and texture of entire sub basins
Basin Name
Dipota Nadi
Jorasar Nadi
Mansari Nadi
Dibru Nadi
Khari Dikrai Nadi
Upar Dikrai Nadi
Daigurang Nadi
Khaina Nadi
Lengtey Nadi
Diju Nadi
Pakke River
Tributary of Pakke River
Tributary of Kameng River
Pasa Nadi
Pani Nadi
Papu River
Chakrasong Nadi
Tributary of Pacha River
Pacha River
Lengpla Nadi
Phuchao Nadi
Kade Nala
Pakoti Nadi
Hoda Nadi
Huduri Nadi
Kaun or Hukubu Nala
Gayang River
Ki Nala
Miao Nadi
Upstream of Dinang Bru
Dibri Bru
Difya River
Khenda Nadi
Taamchin RI (Sashi Chu)
Meni Nadi
Nimsinggoto River
Dublo Kho
Tribtary of Tenga River
Dogong Kho
Sessa Nadi
Tipi Nala
Drainage
Density
Km-1
1.7
1.7
2.0
3.1
3.0
2.7
3.3
3.0
3.2
3.3
3.0
3.3
2.8
2.8
3.7
2.8
2.9
3.0
2.9
3.3
3.1
2.9
3.3
3.2
3.5
3.5
3.1
3.4
3.8
3.8
3.5
3.8
3.5
3.1
3.9
3.6
3.2
3.2
3.3
3.5
3.1
142 Drainage
Frequency
Km-2
1.5
1.5
1.5
4.5
3.2
3.4
4.5
4.5
4.9
4.9
4.3
5.4
4.4
3.9
5.2
3.3
4.5
4.4
3.9
5.9
4.7
4.1
4.9
5.5
5.5
5.0
4.8
5.6
6.9
6.5
5.3
7.4
5.3
4.2
6.2
5.6
4.8
4.5
4.9
5.5
4.3
Drainage
Texture
Km-1
5
2
3
7
6
6
5
8
9
6
10
7
5
8
8
7
7
5
7
6
7
6
11
7
7
7
10
7
7
10
8
8
6
8
9
8
11
8
7
8
7
Basin shape
The shape of the basin mainly governs the rate at which the water is supplied to the
main channel. The main indices used to analyse basin shape and relief are the
elongation and relief ratios. The elongation ratio is calculated by dividing the
diameter of a circle of the same area as the drainage basin by the maximum length of
the basin, measured from its outlet to its boundary. Three parameters viz. Elongation
Ratio (Re), Circulatory Ratio (Rc) and Form Factor (Rf) are used for characterizing
drainage basin shape, which is an important parameter from hydrological point of
view.
Elongation Ratio (Re)
Schumm’s 1956 used an elongation ratio (Re) defined as the ratio of diameter of a
circle of the same area as the basin to the maximum basin length. The value of Re
varies from 0 (in highly elongated shape) to unity i.e. 1.0 (in the circular shape).Thus
higher the value of elongation ratio more circular shape of the basin and vice-versa.
Values close to 1.0 are typical of regions of very low relief, whereas that of 0.6 to 0.8
are usually associated with high relief and steep ground slope (Strahler, 1964).These
values can be grouped as,
Elongation ratio
<0.7
0.8-0.7
0.9-0.8
>0.9
Shape of basin
Elongated
Less elongated
Oval
Circular
The elongation ratio values of the different basins are varies between 0.4 and 1 (Table
5.9). The sub basins of the alluvial region shows low values (0.4-0.5) represent the
elongated basin with low relief. More number of sub basins in the north of MBT
shows oval and circular shape. The circular basin is more efficient in run-off
discharge than an elongated basin (Singh and Singh, 1997). The central parts of the
Jia Bharali catchment the basins are comparatively circular with higher value than the
alluvial and the piedmont zone basin. In the study area among the 41 sub basins 30
sub basins shows elongation value 0.6-0.8 represents high relief and steep ground
slopes.
143 To understand the relationship between bifurcation ratio and the elongation ratio a
regression line is constructed, which show a linear negative relation i.e. with increase
of elongation ratio, bifurcation ratio decrease (Figure 5.18)
Figure 5.18:
Graphical plot of elongation ratio and bifurcation ratio shows
elongated basin have have a high bifurcation ratio. Development of
lower order drainage is more in elongated basins.
Circularity Ratio (Rc)
The circularity ratio is a similar measure as elongation ratio, originally defined by
Miller (1953), as the ratio of the area of the basin to the area of the circle having same
circumference as the basin perimeter. The value of circularity ratio varies from 0 (in
line) to 1 (in a circle). The Circulatory ratio for all basins is in the range of 0.23 to
0.79. The Pakke River shows the lowest value, whereas the Pakoti Nadi shows the
high value of 0.79. Higher the value represents more circularity in the shape of the
basin and vice-versa. Naturally all basins have a tendency to become elongated to get
the mature stage. The observed combination of high Elongation Ratio and Circularity
values, especially in the central part of the basin shows circular in nature. Some of the
basins 6, 9, 16 show complicated value, high circularity ratio as well as the low
elongation ratio. This complicated shape parameter is the result of the presence of a
combination of lithological formations, leading to differential erosion and
consequently to watershed displacement. The circularity ratio shows somewhat lower
values for the basins 11 in eastern part of the study area where there is strong
structural control on the drainage development. Therefore the structural control of
drainage is probably responsible for the low values of circularity ratio.
144 Form Factor (Rf)
Form factor is the numerical index (Horton, 1932) commonly used to represent
different basin shapes. The value of form factor is in between 0.1-0.8. Smaller the
value of form factor, more elongated will be the basin. The basins with high form
factors 0.8, have high peak flows of shorter duration, whereas, elongated drainage
basin with low form factors have lower peak flow of longer duration. The alluvial
basins shows low form factor value represent elongated in nature of the basins. The
basin 13 shows high values of form factor 0.8 is ideal circular basin. The values
indicate the drainage central and western part of the study area shows high values of
form factor. The drainage development in these parts is high and the area has a
structural control.
Relation between different shape parameters
Mutual relationship of these parameters can be evaluated from the plot as shown in
Figure. It is found that for a given drainage basin that the elongation ratio, circularity
ration and form factor show a relationship of decrease in values the order viz.,
elongation ratio ˃ circularity ratio > form factor. The three measures thus are
conformable and suitable for defining basin shape. In four basins viz., 11, 13, 27, 35
the form factor value is complicated from the other value. This represents the
structural control on the basins. The Pakke River (basin index 11) has an elongated
course with curvature basins shape, totally controlled by the major trust, transverse
fault and lithology of the area. Whereas the basins having index 13, 27 and 35 are of
oval shape.
Figure 5.19
Relation between different shape parameters shows a decrease values
i.e. elongation ratio ˃ circularity ratio > form factor
145 Table 5.9
Basin
Index
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
Shape parameters of entire 41 fifth order sub-basin
Basin Name
Circularity
Ratio (Rc)
Elongation
Ratio (Re)
Rc=4πAu/p2
Re=2{√(Au/π)}/Lb
Dipota Nadi
Jorasar Nadi
Mansari Nadi
Dibru Nadi
Khari Dikrai Nadi
Upar Dikrai Nadi
Daigurang Nadi
Khaina Nadi
Lengtey Nadi
Diju Nadi
Pakke River
Tributary of Pakke River
Tributary of Kameng River
Pasa Nadi
Pani Nadi
Papu River
Chakrasong Nadi
Tributary of Pacha River
Pacha River
Lengpla Nadi
Phuchao Nadi
Kade Nala
Pakoti Nadi
Hoda Nadi
Huduri Nadi
Kaun or Hukubu Nala
Gayang River
Ki Nala
Miao Nadi
Upstream of Dinang Bru
Dibri Bru
Difya River
Khenda Nadi
Taamchin RI (Sashi Chu)
Meni Nadi
Nimsinggoto River
Dublo Kho
Tribtary of Tenga River
Dogong Kho
Sessa Nadi
Tipi Nala
146 Form
Factor (Rf)
Rf=Au/Lb2
0.4
0.5
0.2
0.3
0.4
0.1
0.3
0.5
0.2
0.6
0.8
0.5
0.5
0.6
0.7
0.7
0.3
0.4
0.4
0.6
0.2
0.5
0.7
0.4
0.7
0.8
0.6
0.4
0.5
0.2
0.2
0.6
0.3
0.7
0.8
0.6
0.6
0.4
1.0
0.6
0.8
0.3
0.6
0.6
0.3
0.7
0.7
0.4
0.5
0.7
0.4
0.6
0.7
0.8
0.8
0.4
0.6
0.7
0.8
0.5
0.7
0.9
0.6
0.7
0.7
0.4
0.8
0.8
0.5
0.7
0.8
0.5
0.5
0.6
0.3
0.5
0.5
0.2
0.6
0.5
0.9
0.6
0.6
0.3
0.5
0.7
0.4
0.6
0.8
0.5
0.5
0.6
0.6
0.7
0.3
0.3
0.7
0.8
0.5
0.6
0.7
0.4
0.7
0.7
1.0
0.8
0.7
0.6
0.4
0.6
0.3
0.5
0.7
0.4
0.6
0.7
0.4
0.6
0.6
0.3
0.3
0.5
0.2
Infiltration Number (If)
The infiltration Number is defined as the product of Drainage Density (Dd) and
drainage Frequency (Fs). The Jorasar Nadi has the low infiltration 2.5 and the Difya
River has the higher infiltration number of ~ 28.3. The Jorasar basin is found in the
alluvial plain thus it has a higher infiltration. On the other hand the Dify River, in
north of MBT having a higher infiltration number. The higher the infiltration number
the lower will be the infiltration and consequently, higher will be run off. This leads
to the development of higher drainage density. It gives an idea about the infiltration
characteristics of the basin reveals impermeable lithology and higher relief.
Length of Overland Flow (Lg)
The term length of overland is used to describe the length of flow of water over the
ground before it becomes concentrated in definite stream channels. Horton (1945)
expressed it as equal to half of the reciprocal of Drainage Density (Dd). It is an
important independent variable, which greatly affect the quantity of water required to
exceed a certain threshold of erosion. This factor relates inversely to the average slope
of the channel and is quite synonymous with the length of sheet flow to a large
degree. The length of overland flow bears an effective relationship with the drainage
density and constant channel maintenance.
The length of overland flow ranges between 0.1-0.3. Sub basin of alluvial plain
(zone-I) shows high value. Sub basins of zone-II show moderate value of 0.2
whereas the basins of zone-III show the value of 0.1-0.2. The basins north of MBT
show moderate to low value. More the value represents long time of flow in the
basin. The alluvial plain basins are elongated and have a high length of course. The
basins of the central part have a low value, these basins have a drainage density and
runoff is more but they have short course of flow. Smaller the value of overland flow
the quicker surface runoff will enter the streams represents well developed drainage
network with higher slope. In a relatively homogeneous area, therefore less rainfall is
required to contribute a significant volume of surface runoff to stream discharge
when the value of overland flow is small than when it is large. As the western part of
Jia Bharali basin exhibit less rainfall than the other area, it has a quick discharge that
leads to the development of the high drainage density.
147 Constant of Channel Maintenance (C)
This parameter indicates the requirement of units of watershed surface to bear one
unit of channel length. Schumn (1956) has used the inverse of the drainage density
having the dimension of length as a property termed constant of channel
maintenance. The drainage basins having higher values of this parameter, there will
be lower value of drainage density.
All the values are computed and shown in the Table (Table No 5.10). The alluvial and
the piedmont area basins show comparatively high constant channel maintenance.
Diputa Nadi shows highest value of 0.6 km-2 which has the least drainage density,
while Difya River and the Meni Nadi has lowest constant channel maintenance of 0.3
km-2 , and these two basins has the highest drainage density of 3.8 km-1 and 3.9 km-1 .
Higher value of constant channel Maintenance reveals strong control of lithology with
a surface of high permeability. Alluvial basin of plain and piedmont zone shows
highest value, as the permeability in this zone is high.
148 Table 5.10
Basin
Index
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
Computed values of infiltration number, length of overland flow and
constant of channel maintenance
Basin Name
Infiltration
Number
Length of Over
land Flow
If=Dd.Df
Lg=1/2.Au/∑Lu
2.5
2.5
2.9
13.9
9.3
8.9
14.7
13.2
15.8
16.3
12.8
18.0
12.5
10.9
19.4
9.0
13.0
13.0
11.3
19.8
14.6
11.8
16.3
17.7
19.2
17.4
14.8
18.9
26.4
24.4
18.7
28.3
18.2
12.6
24.2
19.8
15.3
14.4
16.3
19.3
13.1
Dipota Nadi
Jorasar Nadi
Mansari Nadi
Dibru Nadi
Khari Dikrai Nadi
Upar Dikrai Nadi
Daigurang Nadi
Khaina Nadi
Lengtey Nadi
Diju Nadi
Pakke River
Tributary of Pakke River
Tributary of Kameng River
Pasa Nadi
Pani Nadi
Papu River
Chakrasong Nadi
Tributary of Pacha River
Pacha River
Lengpla Nadi
Phuchao Nadi
Kade Nala
Pakoti Nadi
Hoda Nadi
Huduri Nadi
Kaun or Hukubu Nala
Gayang River
Ki Nala
Miao Nadi
Upstream of Dinang Bru
Dibri Bru
Difya River
Khenda Nadi
Taamchin RI (Sashi Chu)
Meni Nadi
Nimsinggoto River
Dublo Kho
Tribtary of Tenga River
Dogong Kho
Sessa Nadi
Tipi Nala
149 0.3
0.3
0.3
0.2
0.2
0.2
0.2
0.2
0.2
0.2
0.2
0.2
0.2
0.2
0.1
0.2
0.2
0.2
0.2
0.2
0.2
0.2
0.2
0.2
0.1
0.2
0.2
0.2
0.1
0.1
0.1
0.1
0.1
0.2
0.1
0.1
0.2
0.2
0.2
0.1
0.2
Constant of
Channel
Maintance
C=1/Dd
0.6
0.6
0.5
0.3
0.3
0.4
0.3
0.3
0.3
0.3
0.3
0.3
0.4
0.4
0.3
0.4
0.3
0.3
0.4
0.3
0.3
0.4
0.3
0.3
0.3
0.3
0.3
0.3
0.3
0.3
0.3
0.3
0.3
0.3
0.3
0.3
0.3
0.3
0.3
0.3
0.3
5.4
Relief aspects
Linear and areal features have been considered as the two dimensional aspect lie on a
plan. The third dimension introduces the concept of relief. By measuring the vertical
fall from the head of each stream segment to the point where it joins the higher order
stream and dividing the total by the number of streams of that order, it is possible to
obtain the average vertical fall.
Channel Gradient
Channel Gradient is the total drop in elevation from the source to the mouth of the
trunk channels in each drainage basin. In the present study area Diputa Nadi has the
lowest 1.7 m/km and the Sessa Nadi has the highest gradient of 250.1 m/km (Table
5.11). The alluvial basins shows low channel gradient whereas the basins around
MBT and western part of the basins shows comparatively high value than the eastern
part.
The Kameng River originates in the upper Himalayan ranges at an elevation of
~5400m. Its total route of ~242 km upto its confluence with River Brahmaputra,
carries the discharge of all its major and minor tributaries. The system is characterized
by steep gradient in its initial length of about 40 km from its origin and a much gentle
gradient in the lower reaches of about 200 km before joining River Brahmaputra. Jia
Bharali river show an average gradient of ~22m/km. However, in its upstream course
north of the MCT the gradient is ~112 m/km changing to ~8.3 m/km between MCT
and MBT and ~2.1 m/km between MBT and HFT. The alluvial segment shows a
substantially lower gradient of ~ 0.4 m/km.
Basin Relief (H)
Basin relief is the elevation difference of the highest and lowest point of the valley
floor. The sub basins relief range from 57 to 3207m, whereas the relief of Kameng is
6621m. Basins of north of MBT shows comparatively high relief shows elevation
source of basins of west of Kameng and north of MBT shows relatively high relief
than eastern part. Computed basin relief are tabulated in the Table 5.11
150 Relief Ratio (Rh)
Relief ratio is defined as the ratio between the total relief of a basin i.e. elevation
difference of lowest and highest points of a basin, and the longest dimension of the
basin parallel to the principal drainage line (Schumn 1956).
This is a dimensionless height-length ratio and allows comparison of the relative relief
of any basin regardless of difference in scale or topography. Relief ratio is equal to the
right angled triangle and is identical with the tangent of the angle of slope of the
hypotenuse with respect to horizontal (Strahler, 1964). Thus is measure the overall
steepness of a drainage basin is an indicator of intensity of erosion processes
operating on the slope of the basin.
Relief ratio normally increases with decreasing drainage area and size of a given
drainage basin (Gottschalk, 1964). The Relief Ratio of the fifth-order drainage basins
varies between the values of 0.002 to 0.283 (Table 5.11). Basins’ consisting of
alluvium (Zone-I) shows the low relief ratio. Zone-III basins shows high relief ratio.
The western part of Kameng River, the fifth order basis shows high relief ratio than
the eastern part sub basins. In the zone-II the basins of Siwaliks and piedmont zone
has a low relief ration because of high erodability of the rock type. The high values of
Relief Ratio in the western part can be explained by the presence of highly resistant
rocks of Bomdila group underlying the basin. The high values of Rh indicate steep
slope and high relief and vice-versa. Relief controls the rate of conversion of
potential to kinetic energy of water draining through the basin. Run-off is generally
faster in steeper basins, producing more peaked basin discharges and greater erosive
power.
Ruggedness Number (HD)
Strahler (1968) describes ruggedness number (HD) as the product of maximum basin
relief and drainage density and it usually combines slope steepness with its length.
Extremely high values of ruggedness number occur when slopes of the basin are not
only steeper but long, as well. For the present sub basins, the ruggedness number
151 varies from 0.09 for Diputa Nadi with low sloping area to 10.31 for Sessa Nadi
having higher basin relief with gradual change in slope of uniform nature (Table
5.11). The Zone-I basins shows a low value of ruggedness number, Zone-II basins
shows a moderate value whereas the Zone-III basins shows a high value of
ruggedness number.
The sub basins north of MBT show comparatively high ruggedness number, whereas
the sub basins of western side of Kameng shows high ruggedness number (3.7410.31) than the eastern side (2.66-5.50). The western part is highly dissected as the
high ruggedness number, higher drainage frequency with high channel gradient lead
more erosion and dissection. Basins are comparatively circular with low permeability
with homogeneous lithology reflects the tectonic influence on the basin. The fine to
very fine drainage texture with high relief and comparatively steep slopes leads to
development of high drainage density though the area exhibits less rainfall than the
other part. Drainage density and the lineament density map reflect the influence of
structural disturbance on the area.
152 Table 5.11
Basin
Index
Basin Name
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
Dipota Nadi
Jorasar Nadi
Mansari Nadi
Dibru Nadi
Khari Dikrai Nadi
Upar Dikrai Nadi
Daigurang Nadi
Khaina Nadi
Lengtey Nadi
Diju Nadi
Pakke River
Tributary of Pakke River
Tributary of Kameng River
Pasa Nadi
Pani Nadi
Papu River
Chakrasong Nadi
Tributary of Pacha River
Pacha River
Lengpla Nadi
Phuchao Nadi
Relief parameters of the 5th order sub basins
Elevation of
Elevation of Maximum Maximum
Channel
Relief
Ruggedness
Highest Point on lowest point Basin
Basin
Gradient Ratio
Number
Basin Perimeter at the mouth Relief (H)
Length (Lb)
(Rh)
(HD)
m
m
m
km
m/Km
125
68
57
33.80
0.09
1.7
0.002
357
76
281
27.08
0.49
10.4
0.010
428
76
352
28.81
0.70
12.2
0.012
1560
183
1377
10.82
4.29
127.3
0.127
1130
93
1037
15.36
3.05
67.5
0.068
1472
106
1366
14.42
3.63
94.7
0.095
1126
110
1016
12.49
3.35
81.3
0.081
1763
166
1597
14.06
4.72
113.6
0.114
1232
166
1066
11.28
3.45
94.5
0.095
1366
121
1245
13.84
4.13
89.9
0.090
1926
479
1447
32.55
4.30
44.5
0.044
1285
479
806
7.12
2.66
113.2
0.113
1287
295
992
5.70
2.81
174.0
0.174
2367
678
1689
20.37
4.66
82.9
0.083
2340
895
1445
12.17
5.34
118.8
0.119
3320
1443
1877
15.86
5.16
118.3
0.118
3335
1443
1892
13.41
5.50
141.1
0.141
3040
1481
1559
6.97
4.62
223.6
0.224
3250
1481
1769
10.78
5.13
164.2
0.164
1640
515
1125
5.46
3.76
205.9
0.206
2253
290
1963
8.45
6.07
232.2
0.232
153 Basin
Index
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
Basin Name
Kade Nala
Pakoti Nadi
Hoda Nadi
Huduri Nadi
Kaun or Hukubu Nala
Gayang River
Ki Nala
Miao Nadi
Upstream of Dinang Bru
Dibri Bru
Difya River
Khenda Nadi
Taamchin RI (Sashi Chu)
Meni Nadi
Nimsinggoto River
Dublo Kho
Tribtary of Tenga River
Dogong Kho
Sessa Nadi
Tipi Nala
Elevation of
Elevation of Maximum Maximum
Channel
Relief
Ruggedness
Highest Point on lowest point Basin
Basin
Gradient Ratio
Number
Basin Perimeter at the mouth Relief (H)
Length (Lb)
(Rh)
(HD)
2125
345
1780
10.15
5.15
175.3
0.175
2348
364
1984
12.04
6.63
164.8
0.165
2516
995
1521
7.70
4.92
197.7
0.198
2936
635
2301
10.92
8.04
210.7
0.211
2835
585
2250
14.23
7.78
158.1
0.158
2835
585
2250
13.05
6.90
172.4
0.172
3135
880
2255
10.98
7.63
205.5
0.205
3135
1550
1585
7.22
6.04
219.7
0.220
3605
1550
2055
9.87
7.72
208.2
0.208
3605
1325
2280
12.84
7.98
177.6
0.178
3175
1175
2000
9.09
7.66
219.9
0.220
3080
1570
1510
6.30
5.23
239.6
0.240
3224
1190
2034
12.85
6.20
158.3
0.158
3183
1260
1923
6.79
7.49
283.1
0.283
3340
1578
1762
8.25
6.25
213.6
0.214
2615
1445
1170
24.48
3.74
47.8
0.048
3073
1408
1665
13.32
5.38
125.0
0.125
3259
1280
1979
9.87
6.59
200.4
0.200
3094
165
2929
11.71
10.31
250.1
0.250
3345
138
3207
22.45
9.82
142.8
0.143
154 Hypsometric Curve:
There are two methods to draw a hypsometric curve. In the first type the ordinate is
the percentage of sub-catchments elevation relative to the maximum height of the
basin, while the abscissa is the percentage of the sub-catchment area relative to the
total basin area (Schumm, 1956). The second type pertains to hypsometry of the
individual sub-catchments where the ordinate represents the sub-catchments
elevations (h), normalized against its maximum height (H), while abscissa represents
the corresponding areas (a), normalized against the sub-catchment total area (A)
(Strahler, 1964). The value of relative area (a/A) always varies from 1.0 at the lowest
point in the basin (h/H=0.0) to 0.0 at the highest point in the basin (h/H=1.0).
Hypsometric curves are non-dimensional measure of the proportion of the catchment
area above a given elevation. According to Schumm (1956), Strahler (1964), Leopold
et al. (1964) and Hurtrez et al. (1999), hypsometric curves are related to geomorphic
and tectonic evolution of drainage basins in terms of their forms and processes.
Strahler (1952, 1957, and 1964) identified three types of landforms, namely, young,
mature and monadnock on the basis of hypsometric curve shape.
The second method is used for draw the curve for the entire 41 sub basins. Two
competing factors, namely, tectonic uplift and down wasting due to erosion control
landscape form and its evolution. The shape of hypsometric curves depends on the
degree and type of down wasting. Landscape evolution can be formulated as a
continuity equation relating uplift, elevation and erosion for sediment transport.
(Willgoose and Hancock, 1998). Sub-basins are delineated from the available Survey
of India toposheet. For all the basins the Digital Elevation Model is clipped from the
Shuttle Radar Topography Mission (SRTM) 3-arc second DEM.
The areas are
calculated from the DEM in some equal elevation interval. The resulted hypsometric
curves are shown in the Figure 5.20 to 5.26.
155 Figure 5.20: Hypsometric curve of different fifth order sub basins (having index 1, 2, 3, 4, 5, 6) of the study area (After Strahler, 1952)
156 Figure 5.21: Hypsometric curve of different fifth order sub basins (having index 7, 8, 9, 10, 11, 12) of the study area (After Strahler, 1952)
157 Figure 5.22: Hypsometric curve of different fifth order sub basins (having index 13, 14, 15, 16, 17, 18) of the study area (After Strahler, 1952)
158 Figure 5.23
Hypsometric curve of different fifth order sub basins (having index 19, 20, 21, 22, 23, 24) of the study area (after Strahler, 1952)
159 Figure 5.24
Hypsometric curve of different fifth order sub basins (having index 25, 26, 27, 28, 29, 30) of the study area (after Strahler, 1952)
160 Figure 5.25
Hypsometric curve of different fifth order sub basins (having index 31, 32, 33, 34, 35, 36) of the study area (after Strahler, 1952)
161 Figure 5.26
Hypsometric curve of different fifth order sub basins (having index 37, 38, 39, 40, 41) of the study area (after Strahler, 1952)
162 Longitudinal Profile:
The longitudinal profile of a stream is a property of stream geometry that can provide
clues to underlying materials as well as insights into geologic processes and
geomorphic history of an area (Hack, 1960). The longitudinal profile of a stream
channel may be shown graphically by a plot of altitude (ordinate) as function of
horizontal distance in (abscissa).
The longitudinal profile is a graph of distance verses elevation. The construction of
longitudinal profile provides an interpretation of the surface history as they are the
erosional curves and the river course flows from the source to mouth at any stage of
evolution. (Kumar and Pandey, 1981). Longitudinal Profile for entire 41- 5th Order
sub basin of the Jia Bharali River catchment basins is constructed and shown in
Figure. The streams are taken from the SOI toposheet. The profiles are constructed
considering distance in the abscissa and the elevation as ordinate.
Two types of longitudinal profile can be generated taking the horizontal axes in
arithmetic scale and logarithmic scale keeping the vertical axes in arithmetic scale.
Both the profiles are well representing the structural disturbance along the course and
the lithology beneath the basin. The longitudinal profile constructed taking both scale
arithmetic shows the development of the knick point along the river bed. This knick
point represents the structural disturbance and the lithology control. In most of the
basin structure play a dominant role. All the major thrust and the transverse fault/
lineament are reflects as slope difference along the profile. It is observed that the
basin north of MBT and west of Kameng (basin 21-41), structure and lithology has
major role in the basin whereas in the eastern side basin (basin 11-20) structure play
major role.
It is also observed that basin higher elevation with low relief, in between MBT and
MCT (31, 32, 34, 35, 36, 37, 38, and 39) shows almost smooth river bed profile with a
minute change along lithologic contact. Basin of piedmont zone and south of MBT
shows well development of slope break along the Tipi thrust and other major
lineament. It reflects the streams of this zone are active with any deformation. Basin 2
and 3 shows a great slope break in their course representing the dominant role of
HFT.
163 Figure 5.27
Longnitudianal profile for the Basins of Zone-I (Baisn 1, 2, 3) and Zone-II (Basin 4, 5, 6)
164 Figure 5.28
Longnitudianal profile for the Basins of Zone-II (Basin 7, 8, 9, 10, 11, 12)
165 Figure 5.29
Longnitudianal profile for the Basins of Zone-II (Basin13, 14, 15, 16) and Zone-III (Basin 17, 18)
166 Figure 5.30
Longnitudianal profile for the Basins of Zone-III (Basin 19, 20, 21, 22, 23, 24)
167 Figure 5.31
Longnitudianal profile for the Basins of Zone-III (Basin 25, 26, 27, 28, 29, 30)
168 Figure 5.32
Longnitudianal profile for the Basins of Zone-III (Basin 31, 32, 33, 34, 35, 36)
169 Figure 5.33
Longnitudianal profile for the Basins of Zone-III (Basin 37, 38, 39, 40, 41)
170 171