Bank and Channel Modifications

River Habitat Survey

Preparatory Work

• Get an idea of the site

beforehand:

• Resources

– Maps

– Geographical Information

Systems

– Google Earth

Artificial Features (Section D)

II 2

PHOTOGRAPH

Weirs & Sluices

• Photograph all weirs or sluices

• Major: - permanent

- water-tight

- extend entire width of channel

Major Weir

Weirs & Sluices

• Intermediate

• semi-permeable

• entire width of channel

• loose rubble, inter-locked

• boulders, and logs

• allow water through interstices

Intermediate weir

Weirs & Sluices

• Minor

• Permeable

• temporary structures

• stones, cobbles, pebbles (kiddies weirs)

Culverts

• Arched, enclosed pipe structure

• Channel modification -CV

• Record land use

• Often Artificial Substrate

• NV or NK for other entries unless visible

Bridges

• Major• In-channel support (any width)

OR– wide bridges >25m bank length

• Intermediate • No in-channel support• Abutments 10 - 25m of bank length

• ~Banks often RS / RI around bridges

Major Bridge

Bridges

• Minor - No in-channel supports

- Bank abutments <10m bank length

- Any bridge, irrespective of width, with no abutments on bank e.g. viaducts

Outfalls/Intakes

• Discharge points

• Abstraction points

• Classify by size

• Include aprons, wing-walls & bank

protection in assessment of size

Outfalls/Intakes

• Major - permanent

- >25m bank length

• Intermediate - permanent

- 10 - 25m bank length

• Minor - permanent

- <10m bank length

Outfall/intake

Land Drain - do not record in section D

Fords

• Permanent crossing for vehicles/machinery• Major - Bed is artificial

- Banks can be artificial or natural- Ponding upstream

• Intermediate - Banks artificial material- Channel substrate natural- Slight upstream ponding

• Minor - No artificial bed/bank

Deflectors/Groynes/Croys

• Artificial

• Part-way across channel

• Deflect currents from eroding banks

• Create in-stream habitat diversity, so often used in river enhancement schemes

Deflectors/Groynes/Croys

• Major - Extends >20% channel width

- Includes collapsed weirs

• Intermediate - Extends 10 - 20% channel width

• Minor - Extends <10% channel width

Bank Modification

Principal Bank Modifications recorded by RHS

• RESECTIONED (RS)

• REINFORCED (RI)

• POACHED

• ARTIFICIAL BERM

• EMBANKED

Indicators of Bank Resectioning

• Uniform bank profile

• No trees/uniform age trees

• Intensive land use (eg IG, TL, SU, PG)

• Channel resectioning (see channel modifications)

TIP: Look for RS and RI around bridges, weirs, sluices etc.

Resectioned

Old bank resectioning

• Some reaches may have been resectionedlong ago but are now naturalising

• Record RS on RHS form only where uniform banks remain

• Do not record RS where river processes have reintroduced a more natural bank form

Resectioned & Reinforced banks?

RI WHOLE BANK ONLY

Reinforced

• Whole or part of bank artificially strengthened

• Concrete CC

• Sheet Piling SP

• Wood Piling WP

• Gabions GA

• Brick or Laid Stone BR

• Rip-rap RR

• Tipped Debris TD (IF FOR BANK PROTECTION)

WOOD PILING RI

RIP RAP RI

SHEET PILINGRI WHOLE BANK

BRICK/LAID STONE RI

RS BANKS & CHANNEL,RIP RAP RI, EMBANKMENT

WEIRS

Poached

• Banks trampled/puddled by livestock

• Inc. HEAVILY trampled by humans

• Predominantly bare due to poaching = PC(B)

Artificial Berm

• Bank excavated laterally below bank top, OR Artificial ledges created to reduce low-flow channel width in over-widened channels

Embankments

• Artificial raising of banks

• Little ‘hills’ running along banktop

• If it is resectioned, record RS too

• DO NOT INCLUDE SET-BACKEMBANKMENTS IN SPOT-CHECK

Channel Modifications

Channel Modifications

• Confined to alterations to the bed

• Culvert CV

• Resectioned RS

• Reinforced RI

• Dam/weir/sluice DA

• Fords FO

Indicators of channel resectioning

• Channel

• Overdeepened

• Straightened

• Over-widened

• Uniform/low energy flow types

• Intensive surrounding land-use

• Uniform aged/no bankside trees

• Bank resectioning

Resectioned channel – over-widened

Resectioned channel - realigned

Old channel resectioning

• Resectioned channels may persist longer than resectioned banks

• Where river processes have re-instated more natural channel dimensions or meanders, do not record RS channel

Reinforced channel & banksResectioned channel

Recording Modifications: Spot-check

RS/RI/PC

NKRS/RI* RI EM/RS

* You can only record RS/RI if only part of the bank is reinforced.

RS RS RS RS RS RS RS RSEMRI

E

REMEMBER…….

• Map work before going into the field

• Evidence in field

• Photograph all major and intermediateartificial structures

• Be consistent

• Logical checks

• NK - “Not Known”• investigate before submitting forms.