RP33: Large leaky woody dams
Find out about eligibility and requirements for the large leaky woody dams item.
How much will be paid
£764.42 for each dam
Where to use this item
It is available for Higher Tier and Woodland Creation grants but only:
- in catchments targeted for flood risk measures
- for dams in streams and river channels between 3 metres (m) and 5m
- where approved by the Environment Agency or Lead Local Flood Authority
How this item will benefit the environment
Leaky woody dams slow the movement of water and help push flows onto the floodplain during floods. This increases temporary storage of flood waters within water channels and out on to the floodplain, helping delay the passage of flood water downstream, allowing sediment to settle out, and reduce downstream flood risk.
Requirements
You must:
- follow the indicative drawings in the Higher Tier manual Annex 2c for maximum effectiveness
- construct the dam from logs large enough to span the water channel and out on to the floodplain to provide a stable and long-lasting structure
- secure the dam in line with the requirements of the Environment Agency or Lead Local Flood Authority
- align dams at right angles to channel banks to reduce bank scour
- build dams to allow low flows to pass unimpeded at all times
- site dams on slow flowing reaches of the water course that have on average 2m of floodplain on either side
- build dams to a height sufficient to encourage water to spread onto the floodplain upstream of the dam
- build dams in series (minimum 3 dams) at a spacing between dams of about 5 to 7 times the width of the channel
- make sure dams are not installed directly upstream of pinch points such as bridges or culverts that back up flows and are likely to swamp the dam
- check and maintain dams to keep the structure effective
- follow the requirements set out in any Feasibility Study or Catchment Sensitive Farming (CSF) Design Plan
Keeping records
Before you apply, you must seek advice from the Environment Agency and where relevant the Lead Local Flood Authority to check if you need consent to carry out the planned work.
You must keep the following records and supply them with your payment claim:
- photographs of the completed works in place and installed
- any consents and permissions from the Environment Agency/Local Flood Authority
You must keep the following records and supply them on request:
- receipted invoices, or bank statements where a receipted invoice is unavailable
- photographs of the existing site before work starts
- a copy of the Feasibility Study or woodland management plan or Catchment Sensitive Farming (CSF) design plan (Water-Holding Feature Management Plan), where applicable
- any consents and permissions connected with the work (in addition to the ones stated above)
Please see the record keeping and inspection requirements as set out in the relevant manual (Higher Tier manual or Woodland Creation) for more detail.
Advice and suggestions for how to carry out this item
The following advice is helpful, but they are not requirements for this item.
Detailed design can vary and the siting of leaky woody dams in natural water courses will be dictated by local circumstances and availability of or easy access to import suitable materials to site. Higher Tier manual Annex 2c has details of indicative design of dams.
Check the dams for silt
You will need to check the dam regularly and de-silt it to prevent it collecting large amounts of silt.
Further information
The management of water on the land can be improved by using rural sustainable drainage systems.
Catchment Sensitive Farming (CSF) operates in parts of the country where there are water quality issues linked to farming. The scheme provides farmers with free advice and training. See guidance for further information on CSF support.
See the Higher Tier or Woodland Creation manual to find out more about the scheme and how to apply.
Last updated 15 July 2020 + show all updates
-
Page updated to show latest record keeping
-
Capital item now includes woodland.
-
First published.