Silt control above a SSSI in Lake District National Park

Silt mats preventing sediment from flushing downstream

Silt Mats preventing sediment from flushing downstream

Ullswater is the second largest lake in England, set within the Eden Valley in the heart of the Lake District National Park, famous for its fells, forests, rivers and lakes.

This particular project in Sharrow Bay was to improve the cross-sectional flow of a stone bridge and resurface a washed out path in woodland above Ullswater.

The location boasts dramatic scenery and has nature conservation designations for nationally important aquatic flora and fish species including Site of Special Scientific Interest and Special Area of Conservation.

Steep, impermeable ground and intense rainfall events around Ullswater generate a high volume of surface water run-off that leads to flashy, energetic streams where effective silt control can be a challenge.

Silt is the most common pollutant from construction projects; it can cause environmental degradation by smothering habitats and reducing water quality. Managing silt pollution is particularly important when working upstream of sensitive, protected habitats.

Silt Mats were deployed to prevent mobilised silt from impacting on the important flora and fauna features in Ullswater for the duration of works.

Silt mat full of sediment captured from the stream

Silt Mat full of sediment captured from the stream


Nick Hall, Flood Resilience Ranger for the Lake District National Park, commented

We always try to minimise the environmental impact of our work, so we specified the Silt Mats as mitigation for elevated levels of suspended solids within our SSSI Assent and Habitat Regulations assessment. The mats allowed us to work within the water to increase the abutment height without causing damage to the designated site downstream, with an improvement on the dam style approach of straw bales. The mats were then relocated into the woodland after use, pegged down and seeded, which will allow them to blend in and biodegrade over the coming year.

It is impressive how much silt these mats collect

During the works two lines of Silt Mat were used staggered downstream to control silt pollution. The mats are also able to play a role in controlling erosion in these high-energy environments.

Routes to Resilience, is a programme of works undertaken by Lake District National Park, repairing flood damaged rights of way, in a manner that will allow them to cope with a similar magnitude storm to Storm Desmond 2015 and maintain access to this incredibly valuable natural environment. The programme is funded by the European Agricultural Fund for Rural Development.

frog environmental are proud to support the adoption of best practice for silt management in this sensitive and precious environment.

Find out more about our Silt Mats