BEST PRACTICE GUIDE
VERSION # 1 – APRIL 2013
SMALL STREAM EROSION REPAIR
Details contained in this document have been
prepared to offer assistance to rural landowners,
GWRC staff and Contractors.
The techniques and plans contained in this Guide
have been prepared and included on the basis of
the information accumulated by GWRC and the
experience of GWRC staff over many years in
undertaking and supervising repair work. This is
made available to offer assistance to rural
landowners who experience erosion and are
considering whether or not to undertake repairs.
The guidelines and plans have been compiled to
deal with common or standard situations.
Landowners are cautioned against using the
guidelines and plans in circumstances which may
not be common or standard and are advised to
seek professional assistance if in doubt or where
there has been significant erosion. While GWRC
has endeavoured to ensure the guidelines and
plans are a fair statement of the best practice
derived from experience, it cannot assume
responsibility to any third party for the reliability,
accuracy or completeness of the information or
plans contained in this Guide or of the
applicability of either to any particular
circumstances.
In areas of significant erosion, detailed
engineering investigation / design may be
required.
COVERSHEET
Drawings included within :
•
•
•
•
•
•
•
•
•
•
•
Typical Erosion Scenario
Dwg Ref : RL-5317/01
Willows Driven in at Toe of Bank
Dwg Ref : RL-5317/02
Re-establish Former Channel and Plant Willows
Dwg Ref : RL-5317/03
Taper Back Erosion Face and Plant Willows
Dwg Ref : RL-5317/04
Riparian Strip alongside Stream
Dwg Ref : RL-5317/05
Shift Channel and Construct Tethered Willows
Dwg Ref : RL-5317/06
Tethering (Cabled Willows)
Dwg Ref : RL-5317/07
Tree Groynes (Trenching Willows)
Dwg Ref : RL-5317/08
Hard Edge Works (Concrete Block or Gabion Groynes)
Dwg Ref : RL-5317/09
Pile & Fascine Revetment Protection
Dwg Ref : RL-5317/10
Stock Fence across Small Stream
Dwg Ref : RL-5317/11
For latest version of guide, contact Greater Wellington Regional Council
Flood Protection Department
For more information, contact Greater Wellington:
PO Box 11646
Manners Street
Wellington, 6141
April 2013
File N//50/03/07 v1
e-doc #1178298
T 04 384 5708
F 04 385 6960
www.gw.govt.nz
[email protected]
CROSS SECTION - (Existing situation)
00.
yit 9
./4 Igt it It
N.T.S.
i
Former channel
Erosion face
Gravel beach
Slumping
\
CROSS SECTION - (Situation following erosion)
N.T.S.
Former
channel
New eroded
channel
Eroded Face
PLAN - (Situation following erosion)
N.T.S.
EROSION STARTS
PREVENTING FURTHER EROSION
•
In a flood the stream has greater turbulence and increased energy. Pieces of bank get
carried away causing erosion to stream banks and stream bed.
A variety of methods can be used to try and prevent further erosion.
•
As the volumes and velocities of water increases the stream bed mobilizes and gravel
is transported down the stream.
Some of these methods have been outlined in this drawing series
RL-5317 (Standard Details - River / Small Stream Erosion Repair) by
Greater Wellington's Flood Protection Department.
•
At the erosion site the channel is now wider. As water velocities naturally slow on the
inside of a bend gravel begins to deposit.
The methods attempt to stabilize the stream by addressing
one or more of the issues outlined in the bullet points to the left.
•
A gravel beach builds up opposite the erosion site, narrowing and squeezing the
stream channel and increasing velocities which encourages further bank erosion.
•
As the Stream channel is now narrower, a scour hole has formed exposing raw bank
now at risk of collapse from constant erosion and excavation by the next flood.
VERSION #
1
greater WELLINGTON
REGIONAL COUNCIL
Te Pane IVIatua Taiao
EROSION REPAIR
SMALL STREAM
STANDARD DETAIL
TYPICAL CHANNEL MOVEMENT / EROSION SCENARIO
DESIGN
DRAWN
CHECKED
APPROVED
COMPILED April 2013
April 2013
P.COOK
c. e
—ee:c.--.41-ief
6151/3
Drawing No. RL-5317 / 01
FILE N/50/2/6
Cad: RL-5317_C.dwg
1.11.1..■1 =MINIM=
Former
channel
.00
■■■••°1
0New eroded
0 channel 0
0 00
0 0
Willow poles planted at toe of
eroded bank
PLAN
N.T.S.
Willow poles driven into toe of bank at lm centres.
Plan to have the majority of the pole buried with
approx. 300mm protruding.
Remove build up of
gravelGravel beach
Erosion face
E
E
co
2
,--7.---...
40,,,,t,-;,..1"---:-..-.■
4.164111r2
.......-....Alt
-iiii;',
"----...W1.0 4W-
4 in 1
"., niif Al 111-'10 .
.14 " ' 1 ..-S.1 .jAbw
_C'f,
_ 4.■•••■ 40r..... JO
, ..
0
CD
•••
-Now
r•
"Wier dr. -
ailyw
15.... ....... di,
'.4.
DISCLAIMER:
Toe of bank
Reformed channel
CROSS SECTION
N.T.S.
GWRC and other agencies involved in the preparation of this
plan assume no responsibility as to the reliability, accuracy or
completeness of the information shown or for any interpretation
or action taken by any agency or individual in relation to
information provided on this plan.
This plan has been prepared to offer assistance to rural
landowners, the landowner is under no obligation to carry out
these works. In areas of significant erosion, detailed engineering
design / investigation may be required.
The landowner will need to contact the necessary authorities and
service providers for building consent /resource consent (if
applicable) prior to any work being carried out. Please note there
is always a risk of works being outflanked or destroyed in a flood.
OBJECTIVE
To use willows to secure the eroding bank edge and willow foliage
to protect the upper Erosion face from flood velocities. Regular
removal of gravel build up on the beach opposite is required to
lower the pressure on the willows.
See also caution on cover sheet
PLANTING WILLOW POLES
MATERIALS
Poles should be cut from modern sterile hybrid stock. If poles are purchased the seller should certify
source and breeding. Sterile hybrid willows have been specially developed for river protection work with
extensive root systems, quick growth and large girths while limiting seeding, brittleness and wild strike.
Use cut poles of a multi-stemmed Osier willow e.g. Salix Purpurea
'Booth'. Poles should be 50mm 0 Min. Plan to have the majority of
the pole buried with 300mm approx. protruding.
Use a heavy steel bar to prepare a hole if possible, then drive in
the willow pole. Plant poles at lm spacing.
The preferred osier willow is Salix Matsudana x Salix alba sterile hybrid "Moutere". These willows reach
up to 6m in 2yrs or > 20m on maturity.
LIKELIHOOD OF SUCCESS
Willow poles should be collected and planted when the tree is dormant (June - July). To ensure success
the poles should be planted immediately after collection. If kept moist, poles will remain viable for a
considerable time.
Initially low until willows establish an effective root system. This
could take up to 4 - 5 years in difficult soils.
Perseverance, timely maintenance and no floods during
establishment may assist with success.
Hand planting in gravel should be assisted by an excavator or bulldozer with a ripping tyne or a tractor
with a motorized auger.
To guarantee success poles must be planted deep enough to ensure their root system has access to
moisture all year round. This means plant as deep as practical.
NOTES:
Not appropriate where significant assets are at risk.
Not practical if scour hole is too deep.
Not practical in large gravels.
Must be protected from grazing stock.
Vulnerable to abrasion damage in floods.
VERSION #
1
greater WELLINGTON
REGIONAL COUNCIL
Te Pane Matua Taiao
In silty soils it is often possible to drive poles in by hand. A heavy steel bar is useful to prepare a hole.
Often a fence post hand driver can be use to drive large poles. An end cap can be made from a length of
suitable steel tube. This is slid over the poles and then the pole driven in with a heavy hammer. Allow to
cut the damaged top off the pole with a chain saw.
An excavator can sometimes be used to push poles into place.
EROSION REPAIR
SMALL STREAM
STANDARD DETAIL
WILLOWS DRIVEN IN AT TOE OF BANK
COMPILED April 2013
April 2013
DRAWN
P.COOK
e cp/AKileJ Sisit
CHECKED
APPROVED ..--(--4-4et 6
Drawing No. RL-5317 / 02
DESIGN
FILE N/50/2/6 Cad: RL-5317_C.dwg
DISCLAIMER:
GWRC and other agencies involved in the preparation of this plan assume no
responsibility as to the reliability, accuracy or completeness of the information shown
or for any interpretation or action taken by any agency or individual in relation to
information provided on this plan.
This plan has been prepared to offer assistance to rural landowners, the landowner is
under no obligation to carry out these works. In areas of significant erosion, detailed
engineering design / investigation may be required.
The landowner will need to contact the necessary authorities and service providers for
building consent/resource consent (if applicable) prior to any work being carried out.
Please note there is always a risk of works being outflanked or destroyed in a flood.
See also caution on cover sheet.
■■■■
Former
channel
Erosion bay filled with
gravel and planted willows.
PLAN
N.T.S.
Plant 50mm 0 x 1.5m long willow
poles lm deep @ 1.5m centres
Erosion face ,
Fill eroded channel
with gravel from
beach opposite
Former eroded
channel / scour
hole
\z Gravel removed from
beach to fill eroded
channel
aat Paw
,r,eit,
. 11.110,
111111.7,N,Nor...
FAVa. 404 e,
-.1.11,■*2
z
■S-1 AVZ-r.
/14
-M1211P4.
dor.—
.■■■
ao,-"
•■■•
Fill eroded channel with
OBJECTIVE gravel from beach opposite
CROSS SECTION
Reformed
channel
N.T.S.
To reduce the risk of further damage by shifting the channel off the
Erosion face and planting willow poles to prevent the channel
returning
PLANTING WILLOW POLES
MATERIALS
Use cut poles of a multi-stemmed Osier willow e.g. Salix Purpurea
'Booth' . Poles should be 50mm 0 Min. x 1.5m long.
METHOD
Poles should be cut from modern sterile hybrid stock. If poles are purchased the seller should certify
source and breeding. Sterile hybrid willows have been specially developed for river protection work with
extensive root systems, quick growth and large girths while limiting seeding, brittleness and wild strike.
The preferred osier willow is Salix Matsudana x Salix alba sterile hybrid "Moutere". These willows reach
up to 6m in 2yrs or > 20m on maturity.
Use an excavator to shift the channel off the erosion by using
gravels from the beach opposite. Plant poles lm in and 0.5m out @
1.5m centres in shifted gravel as work proceeds. Alternatively push
poles into loose gravels with digger bucket.
Willow poles should be collected and planted when the tree is dormant (June - July). To ensure success
the poles should be planted immediately after collection. If kept moist, poles will remain viable for a
considerable time.
If the worked gravels are silty, establishing a grass cover may help
with protection.
Hand planting in gravel should be assisted by an excavator or bulldozer with a ripping tyne or a tractor
with a motorized auger.
LIKELIHOOD OF SUCCESS
To guarantee success poles must be planted deep enough to ensure their root system has access to
moisture all year round. This means plant as deep as practical.
Reasonable, provided damage is repaired quickly. Losses are likely
in the initial years as the willows establish (up to 3 - 5 years). The
loose gravel is also vulnerable to further erosion in a flood
Note :
Not appropriate where significant assets are at risk.
Must be protected from grazing stock.
VERSION #
1
greater WELLINGTON
REGIONAL COUNCIL
Te Pane Matua Taiao
In silty soils it is often possible to drive poles in by hand. A heavy steel bar is useful to prepare a hole.
Often a fence post hand driver can be use to drive large poles. An end cap can be made from a length of
suitable steel tube. This is slid over the poles and then the pole driven in with a heavy hammer. Allow to
cut the damaged top off the pole with a chain saw.
An excavator can sometimes be used to push poles into place.
EROSION REPAIR
SMALL STREAM
STANDARD DETAIL
RE-ESTABLISH Former channel and PLANT WILLOWS
DESIGN
DRAWN
CHECKED
COMPILED
P.COK
_April 2013
April 2013
c,se, Ott4AP4
APROVED
Drawing No. RL-5317 / 03
(45,112
FIE N/50/2/6 Cad: RL-5317_C.dwg
DISCLAIMER:
GWRC and other agencies involved in the preparation of this
plan assume no responsibility as to the reliability, accuracy or
completeness of the information shown or for any interpretation
or action taken by any agency or individual in relation to
information provided on this plan.
This plan has been prepared to offer assistance to rural
landowners, the landowner is under no obligation to carry out
these works. In areas of significant erosion, detailed engineering
design /investigation may be required.
The landowner will need to contact the necessary authorities and
service providers for building consent/resource consent (if
applicable) prior to any work being carried out. Please note there
is always a risk of works being outflanked or destroyed in a flood.
See also caution on cover sheet.
\—
Plant 50mm 0 x 1.5m long willow
poles 1 m deep @ 1.5m centres.
First row placed at water level
Erosion face
Former eroded channel
/ scour hole
Cut the Erosion
face back to a
stable slope.
CROSS SECTION
N.T.S.
OBJECTIVE
PLANTING WILLOW POLES
To reduce the risk of further erosion by increasing the waterway
width and thereby lowering velocities. To improve stability at the
site by taking the Erosion face back to a more suitable slope and
planting willows
Poles should be cut from modern sterile hybrid stock. If poles are purchased the seller should certify
source and breeding. Sterile hybrid willows have been specially developed for river protection work with
extensive root systems, quick growth and large girths while limiting seeding, brittleness and wild strike.
MATERIALS
The preferred osier willow is Salix Matsudana x Salix alba sterile hybrid "Moutere". These willows reach
up to 6m in 2yrs or > 20m on maturity.
Use cut poles of a multi-stemmed Osier willow e.g. Salix Purpurea
'Booth'. Poles should be 50mm 0 Min. x 1.5m long.
METHOD
Use an excavator to cut the eroded face back to a stable slope.
Plant poles lm in and 0.5m out @ 1.5m centres. in the cut face
with first row at the waterline.
LIKELIHOOD OF SUCCESS
Willow poles should be collected and planted when the tree is dormant (June - July). To ensure success
the poles should be planted immediately after collection. If kept moist, poles will remain viable for a
considerable time.
Hand planting in gravel should be assisted by an excavator or bulldozer with a ripping tyne or a tractor
with a motorized auger.
To guarantee success poles must be planted deep enough to ensure their root system has access to
moisture all year round. This means plant as deep as practical.
Reasonable. Increases with time as willows establish (up to 3 -5
years) but perseverance, timely maintenance and few floods will
increase success.
In silty soils it is often possible to drive poles in by hand. A heavy steel bar is useful to prepare a hole.
Often a fence post hand driver can be use to drive large poles. An end cap can be made from a length of
suitable steel tube. This is slid over the poles and then the pole driven in with a heavy hammer. Allow to
cut the damaged top off the pole with a chain saw.
Note :
An excavator can sometimes be used to push poles into place.
Not appropriate where significant assets are at risk.
Must be protected from grazing stock.
EROSION REPAIR
greater WELLINGTON
REGIONAL COUNCIL
Te Pane Matua Taiao
SMALL STREAM
STANDARD DETAIL
TAPER BACK Erosion face and PLANT WILLOWS
Drawing No. RL-5317 / 04
FILE N/50/2/6
Cad: RL-5317_C.dwg
Open pasture
T: b. al Sit tie Eroding bank
la!‘ '41,1414 IP1,
'I
Former channel
Gravel beaches
Slumpin
DISCLAIMER:
EXISTING PROFILE
(Showing erosion)
GWRC and other agencies involved in the preparation of this
plan assume no responsibility as to the reliability, accuracy or
completeness of the information shown or for any interpretation
or action taken by any agency or individual in relation to
information provided on this plan.
N.T.S.
This plan has been prepared to offer assistance to rural
landowners, the landowner is under no obligation to carry out
these works. In areas of significant erosion, detailed engineering
design /investigation may be required.
15 - 20m Riparian Strip alongside stream
(interplanted with natives)
The landowner will need to contact the necessary authorities and
service providers for building consent /resource consent (if
applicable) prior to any work being carried out. Please note there
is always a risk of works being outflanked or destroyed in a flood.
Rear trees thinned and topped
as appropriate to rejuvenate and
promote establishment of native
species
See also caution on cover sheet
Salix Matsudana 'Moutere'
at 2.5m spacing
Front edge trees layered
as appropriate to thicken
protection
Fencing
to control
stock
Fencing where
appropriate
41Piiiloii-i■-,
— ',
-4"-,s04.
Beach metal bladed against
willows in the initial years as
required to protect and promote
establishment
.,..0
_____ ....
41.--,411..
.4......
.
e
;0
... .0./
..,..,,..*.orz,-....___
111-
.... ....
...
■
..."0,,,,,r,
_gefire,"
I
m
.....1,.-. r
dozt..7
4,
.....p.7
-,......
-,,_
.710
4514
4 ,„.....4.x....■
4.4y,":".i..
-411 ......,,....47.141r.r...
..-7:.■-isal--......
is -50-.4-4).%,...e.",„,....1c---,,...
0411111EIN,
Former eroded channel / scour
hole
PROPOSED PROFILE
.. 4,..:
N.T.S.
Reformed channel
PLANTING WILLOW POLES
Poles should be cut from modern sterile hybrid stock. If poles are purchased the seller should certify source and breeding. Sterile hybrid willows have been specially developed
for river protection work with extensive root systems, quick growth and large girths while limiting seeding, brittleness and wild strike.
The preferred osier willow is Salix Matsudana x Salix alba sterile hybrid "Moutere". These willows reach up to 6m in 2yrs or > 20m on maturity.
Willow poles should be collected and planted when the tree is dormant (June - July). To ensure success the poles should be planted immediately after collection. If kept moist,
poles will remain viable for a considerable time.
Hand planting in gravel should be assisted by an excavator or bulldozer with a ripping tyne or a tractor with a motorized auger.
To guarantee success poles must be planted deep enough to ensure their root system has access to moisture all year round. This means plant as deep as practical.
In silty soils it is often possible to drive poles in by hand. A heavy steel bar is useful to prepare a hole. Often a fence post hand driver can be use to drive large poles. An end cap
can be made from a length of suitable steel tube. This is slid over the poles and then the pole driven in with a heavy hammer. Allow to cut the damaged top off the pole with a
chain saw.
An excavator can sometimes be used to push poles into place.
VERSION #
DESIGNCOMPILED
1
greater WELLINGTON
REGIONAL COUNCIL
Te Pane Matua Taiao
STANDARD DETAIL
RIPARIAN STRIP ALONGSIDE STREAM
APPROVED
.05e,--4ZW 6ig )1?
Drawing No. RL-5317 / 05
FIE N/50/2/6
Cad: RL-5317_C.dwg
Optional wire rope looped
around willows and tied to
anchors
Alternative driven
anchor
DETAIL
N.T.S.
Tethered willows. Cover with gravel,
sticking out. Cabled together as shown,
anchored every 5 - 10m (depending on
willow size)
Gravel removed from
beach to fill eroded
channel
Erosion face
go .
1-.4tP6r,
sit.
:Op
go
41164.
4.
Wire rope
.
•
.4Arrott —
Aik
Wire rope
Concrete block
anchor (optional)
Former eroded
channel / scour
hole
Reformed channel
DISCLAIMER:
Concrete block
anchor
CROSS SECTION
N.T.S.
GWRC and other agencies involved in the preparation of this
plan assume no responsibility as to the reliability, accuracy or
completeness of the information shown or for any interpretation
or action taken by any agency or individual in relation to
information provided on this plan.
This plan has been prepared to offer assistance to rural
landowners, the landowner is under no obligation to cany out
these works. In areas of significant erosion, detailed engineering
design / investigation may be required.
OBJECTIVE
The landowner will need to contact the necessary authorities and
service providers for building consent/resource consent (if
applicable) prior to any work being carried out. Please note there
is always a risk of works being outflanked or destroyed in a flood.
To reduce the risk of further erosion by shifting the channel off the
erosion and construct a barrier of live willows. The bundled
willows provide a physical barrier (which increases as they grow)
against stream velocities.
See also caution on cover sheet.
MATERIALS
PLANTING WILLOW POLES
Use large branches of tree willows (Matsuda or similar preferred)
Heavy wire rope.
Concrete blocks or Rail irons as anchors.
Poles should be cut from modern sterile hybrid stock. If poles are purchased the seller should certify
source and breeding. Sterile hybrid willows have been specially developed for river protection work with
extensive root systems, quick growth and large girths while limiting seeding, brittleness and wild strike.
METHOD
The preferred osier willow is Salix Matsudana x Salix alba sterile hybrid "Moutere". These willows reach
up to 6m in 2yrs or > 20m on maturity.
Use an excavator to shift the channel off the erosion. Excavate a
trench and place large willow branches in a bundle in the trench.
Place on a slope with their butts in the water and their branches
up (refer to diagram top of page). Tie down securely with wire
rope to the anchors (either concrete blocks or driven Rail irons).
Willow poles should be collected and planted when the tree is dormant (June - July). To ensure success
the poles should be planted immediately after collection. If kept moist, poles will remain viable for a
considerable time.
Use excavator to throw gravel over the willows so they are
Hand planting in gravel should be assisted by an excavator or bulldozer with a ripping tyne or a tractor
with a motorized auger.
covered -31 out
To guarantee success poles must be planted deep enough to ensure their root system has access to
moisture all year round. This means plant as deep as practical.
LIKELIHOOD OF SUCCESS
Good provided they stay well secured and any maintenance is
carried out promptly.
NOTES:
Must be protected from grazing stock.
Not appropriate where significant assets are at risk.
VERSION #
1
greater WELLINGTON
REGIONAL COUNCIL
Te Pane Matua Taiao
In silty soils it is often possible to drive poles in by hand. A heavy steel bar is useful to prepare a hole.
Often a fence post hand driver can be use to drive large poles. An end cap can be made from a length of
suitable steel tube. This is slid over the poles and then the pole driven in with a heavy hammer. Allow to
cut the damaged top off the pole with a chain saw.
An excavator can sometimes be used to push poles into place.
EROSION REPAIR
SMALL STREAM
STANDARD DETAIL
SHIFT CHANNEL and CONSTRUCT
TETHERED WILLOWS
DESIGN
COMPILED
DRAWN
P.COOK
CHECKED
C. C. 44,14/1A1
APPROVED
Drawing No. RL-5317 / 06
April 2013
April 2013
6151i?
FILE N/50/2/6 Cad: RL-5317_C.dwg
Willows
Wire rope to be looped
around willows
2.5m
Concrete blocks
Preferred channel
alignment / design
channel alignment
PLAN
N.T.S.
Preferred channel alignment/
design channel alignment
12mm diameter wire rope
Willows
9
00gt
g
tg
9,0gogogo.
g
.
0.2m - 0.3m
1.4gogilAr'
ELEVATION
N.T.S.
DISCLAIMER:
GWRC and other agencies involved in the preparation of this
plan assume no responsibility as to the reliability, accuracy or
completeness of the information shown or for any interpretation
or action taken by any agency or individual in relation to
information provided on this plan.
This plan has been prepared to offer assistance to rural
landowners, the landowner is under no obligation to carry out
these works. In areas of significant erosion, detailed engineering
design /investigation may be required.
The landowner will need to contact the necessary authorities and
service providers for building consent/resource consent (if
applicable) prior to any work being carried out. Please note there
is always a risk of works being outflanked or destroyed in a flood.
NOTES:
•Where the willow trees or branches overlap, the
upstream willow is to be on the outside (riverside).
See also caution on cover sheet.
VERSION #
1
greater WELLINGTON
REGIONAL COUNCIL
Te Pane IVIatua Taiao
EROSION REPAIR
SMALL STREAM / RIVER
STANDARD DETAIL
TETHERING (CABLED WILLOWS)
DESIGN
COMPILEDApril 2013
DRAWN
April 2013
P.COOK
3pr/0
C - C-44(4414
CHECKED
APPROVED
10E01
Drawing No. RL-5317 / 7
FILE N/50/2/6
Cad: RL-5317_C.dwg
10m crs
NOTES:
Wire rope to be looped
around willows
•Where the willow trees or branches overlap, the
upstream willow is to be on the outside (riverside).
Willows
DISCLAIMER:
GWRC and other agencies involved in the preparation of this
plan assume no responsibility as to the reliability, accuracy or
completeness of the information shown or for any interpretation
or action taken by any agency or individual in relation to
information provided on this plan.
0.8m x 0.8m x 1.6m
concrete blocks
This plan has been prepared to offer assistance to rural
landowners, the landowner is under no obligation to carry out
these works. In areas of significant erosion, detailed engineering
design / investigation may be required.
The landowner will need to contact the necessary authorities and
service providers for building consent/resource consent (if
applicable) prior to any work being carried out. Please note there
is always a risk of works being outflanked or destroyed in a flood.
Wire rope to be
looped around
willows
See also caution on cover sheet.
<
Willows
NN
30°
Wire rop looped
around willows
Willows
/
/12mm Dia.
Wire rope
12mm Dia.
Wire rope
0.8m x 0.8m x 1.6m
concrete blocks
PLAN
ELEVATION
N.T.S.
N.T.S.
VERSION #
1
greater WELLINGTON
REGIONAL COUNCIL
Te Pane Matua Taiao
Tree root
system
EROSION REPAIR
SMALL STREAM / RIVER
STANDARD DETAIL
TREE GROYNES (TRENCHING WILLOWS)
DESIGN
COMPILED April 2013
April 2013
DRAWN
P.COOK
C-C-MAktiki 315111
CHECKED
APPROVED
c/10
Drawing No. RL-5317 / 8
FILE N/50/2/6
Cad: RL-5317_C.dwg
Preferred Channel
Concrete block /
gabion groyne
Gravel removed
from beach to fill
■eroded channel
Erosion face
DISCLAIMER:
GWRC and other agencies involved in the preparation of this
plan assume no responsibility as to the reliability, accuracy or
completeness of the information shown or for any interpretation
or action taken by any agency or individual in relation to
information provided on this plan.
Reformed
channel
Former eroded
channel / scour
hole
This plan has been prepared to offer assistance to rural
landowners, the landowner is under no obligation to carry out
these works. In areas of significant erosion, detailed engineering
design / investigation may be required.
TYPICAL CROSS SECTION
N.T.S.
The landowner will need to contact the necessary authorities and
service providers for building consent /resource consent (if
applicable) prior to any work being carried out. Please note there
is always a risk of works being outflanked or destroyed in a flood.
Plant willows
between groynes
Front edge of top block
In-line with edge of
preferred channel
Preferred edge of
channel
_
See also caution on cover sheet.
Plant willows between
groynes \,/
NINON
Front edge of top block
In-line with edge of
preferred channel
1
,.
. 1
,.1
1
Y
.I<
)
.1/
6 BLOCK
GROYNE
N.T.S.
First row of blocks dug
into bed below scour
depth
3 BLOCK
GROYNE
Preferred edge of channel
N.T.S.
OBJECTIVE
To repair the existing erosion and return the channel to its prior
alignment and hold it there by constructing hard edge works with
either concrete blocks or gabion baskets.
All blocks to be roped together with 14mm 0 wire rope so they
act as a single unit.
It is essential that the bottom layer of blocks is below scour depth
or the groynes will rapidly fail.
MATERIALS
Use 0.8m x 0.8m x 1.6m concrete blocks (or similar) preferably
with centre holes or lifting eyes for wire rope to loop through.
14mm 0 wire rope.
Wire clamps.
Tree willow poles (Moutere).
The area between the groynes is then mass planted with willow
poles.
METHOD
LIKELIHOOD OF SUCCESS
Use an excavator to shift the flow channel back to its pre-erosion
alignment. Fill the current erosion with gravel excavated from the
proposed 'restored channel alignment or from the built up
beaches opposite.
Good, provided the bottom layer is well founded below scour
depth and all blocks secured together with wire rope to act as one
unit.
The large groyne (6 block) is normally used at the apex of the
bend.
NOTES:
Construct a series of concrete block groynes along the outside
edge of the alignment. Blocks set back to of block length and
roped together securely.
Groyne spacing is a judgment call depending on factors such as
tightness of the bend, stream gradient and bank material etc. A
general rule of thumb is : Groyne spacing = 1.5 x the distance
between Erosion face and preferred channel alignment
Willows must be protected from grazing stock.
Gabions may be substituted for concrete blocks (all the above
applies except that in some circumstances gabions have a
shorter life).
Gabions will likely be damaged & fail in highly mobile gravel beds.
Refer to drawings HR-5317 / 2 to 4 for notes on planting willows
Install groyne pointing slightly upstream with a slight lean forward
VERSION #
1
greater WELLINGTON
REGIONAL COUNCIL
Te Pane Matua Taiao
EROSION REPAIR
SMALL STREAM
STANDARD DETAIL
Hard Edge Works (Concrete Block or Gabion Groynes)
DESIGN
COMPILED April 2013
DRAWN
April 2013
P.COOK
C-C-Atidtant
CHECKED
315-1)3
APPROVED_C/16Q. bj 51 1.3
Drawing No. RL-5317 / 09
FILE N/50/2/6
Cad: RL-5317_C.dwg
Fascine of willows placed horizontally
between river bank and piles
Willow poles
NOTES:
•
All irons to be in good condition without significant
corrosion.
•
Wire cable to be 14mm 0 3 x 19 Galvanised wire
rope.
•
Cables tied off every eighth iron (28m).
•
Cable tensioned to a nominal strain using a
"come-along" or 'Tuner winch.
•
In each bay the fascine is to be cabled together and
weighted with a 2.5 tonne concrete anchor block
located immediately underneath the fascine.
•
Every set of three adjoining Railway irons to be tied
back to a 2.5 tonne concrete anchor block located
10m from the line of the rail piles and buried lm Min.
below ground level.
•
Where the willow trees or branches overlap, the
upstream willow is to be on the outside (riverside).
•
Rail piles to be located on the river design channel /
preferred channel alignment. The area between the
river bank and piles is to backfilled with river gravels
as necessary.
•
At the upstream end the rail piles and wire cables
are to be returned into the bank as a Rail iron groyne
4 bays into the bank.
•
Refer also GWRC Drawing A2-9459 / 1-RC for
further details.
,0.1m
0.5m
Concrete anchor
block every wired to
3 rail piles and
buried 1m Min. ,
below ground 1 vel
0.5m
Low flow
water level
River bank
14mm 0 wire
rope
3 wire cables
connecting piles.
Bottom cable
located at water
level
DISCLAIMER:
GWRC and other agencies involved in the preparation of this
plan assume no responsibility as to the reliability, accuracy or
completeness of the information shown or for any interpretation
or action taken by any agency or individual in relation to
information provided on this plan.
This plan has been prepared to offer assistance to rural
landowners, the landowner is under no obligation to cany out
these works. In areas of significant erosion, detailed engineering
design / investigation may be required.
Fascine wrapped together
each bay (10.5m) with
14mm 0 wire rope and
weighed down with a 2.5
tonne concrete anchor block
located immediately
underneath fascine
70 lb yard Rail iron
piles or similar.
The landowner will need to contact the necessary authorities and
service providers for building consent/resource consent (if
applicable) prior to any work being carried out. Please note there
is always a risk of works being outflanked or destroyed in a flood.
DETAIL
See also caution on cover sheet.
N.T.S.
10m
Willow poles
Willow fascine
14mm 0 Wire rope
Concrete block
anchor
.2.gogo
Low flow
water level
V
Erosion face
gi%Z:44g,c;g
ggg4zgzggg
0`4,gg'4,ggggg
14mm 0 wire rope
Concrete block
anchor
Min. bed level /
scour depth
Rail pile
CROSS SECTION N.T.S.
VERSION #
1
greater WELLINGTON
REGIONAL COUNCIL
Te Pane Matua Taiao
EROSION REPAIR
SMALL STREAM / RIVER
STANDARD DETAIL
PILE and FASCINE REVETMENT PROTECTION
DESIGN
COMPILED April 2013
DRAWN
April 2013
P.COOK
CHECKED c-mcfmA4 3/5113
APPROVED
6is713
Drawing No. RL-5317 / 10
FILE N/50/2/6
Cad: RL-5317_C.dwg
NOTES:
To suit site
(but not too heavy)
100 x 50 horizontal timbers
facing downstream side
•
These gates float in a flood and pose minimum
restriction to flows and catch minimum debris.
•
All timber to be treated as required
DISCLAIMER:
GWRC and other agencies involved in the preparation of this
plan assume no responsibility as to the reliability, accuracy or
completeness of the information shown or for any interpretation
or action taken by any agency or individual in relation to
information provided on this plan.
This plan has been prepared to offer assistance to rural
landowners, the landowner is under no obligation to carry out
these works. In areas of significant erosion, detailed engineering
design / investigation may be required.
100 x 20 or 150 x 25
timber
To suit
site
The landowner will need to contact the necessary authorities and
service providers for building consent/resource consent (if
applicable) prior to any work being carried out. Please note there
is always a risk of works being outflanked or destroyed in a flood.
See also caution on cover sheet.
Swinging gate detail
Fix wire hangers so gates can't slide
out of position
N.T.S.
Hang so timber is just out of the water in normal winter flow
Loose chain gates together so
stock can't push through
Heavy wire rope
Cut groove for wire rope at
top of strainer posts
Tie back to ground
anchor
4,1
Wire rope to buried anchor eg. concrete
block
Iktsk
Strainer posts 1m
Min. from bank edge
TYPICAL DETAIL OF STREAM CROSSING
N.T.S.
Strainer post
Strainer post
Swinging gate
100 x 100 timber rail
Wire rope
Fix wire rope here
Strainer post
Tie back to bottom
of post
Alternative for strainer unit
N.T.S.
EROSION REPAIR
greater WELLINGTON
REGIONAL COUNCIL
Te Pane Matua Taiao
SMALL STREAM
STANDARD DETAIL
STOCK FENCE ACROSS SMALL STREAM
DESIGN
DRAWN
COMPILED
CHECKEDC—C, MwAtAt
APPROVED
Drawing No. RL-5317 / 11
FILE N/50/2/6
P.COK
3t5-/i3
61C1
Cad: RL-5317_C.dwg