SCRT have completed a three phased Natural Flood Management (NFM) project on Reston Scar, above Staveley.
The aim of the project at Reston Scar is to ‘test and trial’ new techniques to reduce flood risk for rural communities. Several leaky timber structures have been installed as well as undertaking drainage works to store, divert and slow flows during storm events. See our NFM page for more information about NFM techniques.
This project was supported by two landowners on Reston Scar and Black Crag, who utilise their land for beef and sheep production. The land was made available to demonstrate how agricultural land can be used to ‘slow the flow’ and protect residents in their local communities whilst maintaining traditional farming practices.
Phase one delivered in Summer 2020.
Leaky dams and ‘Kerplunk’ structures
Leaky dams are engineered timber structures, designed to mimic the NFM attributes of naturally fallen trees. They work by temporarily slowing and/or ‘storing’ water during storm events and installed to address river and surface flow flood risks. Leaky dams are designed and built to avoid impacts on normal flows, ecology of the watercourse and impacts on farm land.
These structures are designed to be more open in form than dams. Logs are installed at a variety of heights to capture and slow flood events of varying magnitude. They do this by adding roughness to the channel to slow flood flows, delaying the intensity and timing of peaks downstream.
Timber (Larch) was felled from a plantation near to the project site. The transportation of the timber to and around the sites was particularly challenging, due to elevation, gradient and ground conditions. A low ground pressure tractor fitted with a cable winch, was used help move the timber to the location of each intervention. The terrestrial habitats on Black Crag are especially sensitive and the low ground pressure plant did not break ground or cause any damage to the ecology of the site.
In total six leaky dams and three ‘Kerplunk’ slow the flow structures and short section of earth bund were installed at the site. The dams installed were large features up to 21 metres wide and 1.5 metres high. There was an element of dynamic design to each installation, to accommodate the unique characteristics of each site.
Surface flow disruption
Surface flow or surface runoff is water occurring on the ground surface when excess rainwater or other sources, can no longer rapidly infiltrate soil. A track leading down to Staveley from Reston Scar was a major flow pathway which was identified as a source of flooding.
A significant proportion of the problematic surface flow pathway has now be re-directed from the track into a natural depression in the nearby fields where it will drain slowly into the ground. This was done by adding culverted sections, cross drains and by carrying out track improvements.
Phase two of this project was undertaken in Winter 2020 and saw the further installation of three large leaky dams and three kerplunk structures.
In February 2021, phase three created a flow diversion pathway around Reston Hall to help channel high flows away from at risk properties and thus completing the project.
Here are some photographs of the works;
We will be undertaking a monitoring programme shortly, to help us understand how the structures are functioning under different conditions. If you live locally and would be interested in volunteering e.g. taking photos during different weather events, please get in touch
With special thanks to Catchment Designs Ltd team, Simon and Matt for scoping and delivering this first class project for us.