River Tame – Design and erosion control

Severe erosion of the right-hand bank of the River Tame


The natural river processes had resulted in the deposition and migration of a gravel bar within the River Tame adjacent to the Reddish Vale Country Park. This morphological change resulted in the main flow of the river adjusting towards the true right-hand bank, leading to severe erosion and undercutting of the bank.

Cain Bio-Engineering were contacted by the client to advise the design and reinstatement of the riverbank in three key locations and to provide a solution to prevent future natural channel adjustment destabilising the banks in this area.

 Severe erosion of the right-hand bank of the River Tame in Reddish Vale resulting from natural channel adjustment upstream. The image below shows the 15m length of cliff erosion, though the total length of works required is nearly 40ms.

Before: Bank erosion along the River Tame within Reddish Vale Country Park, Stockport.

The original consent obtained by the client was for a rip-rap bank protection using rock rolls & geotextile matting. However, after a review by CBE an alternative solution, using cheaper and more sustainable materials was developed. The chosen solution involved the construction of an erosion-resistant and natural-looking bank revetment utilising willow spilling with a geotextile and gravel-retained ‘coirnet’ on the landward side. The works also incorporated live willow woody material to help deflect flow away from the bank.

Willow spiling revetment installed to form a new bank line.

Gravel backfilled behind the willow spiling.

Backfilled revetment

The existing bank is then regraded behind the new revetment.

Regraded bank is covered with a biodegradable geotextile.

 

A thin layer of soil was then placed over the geotextile.

Woody debris (live willow) installed at the upstream end of the revetment.

The completed works successfully reinstated the eroded bank margin along the River Tame. The final photo shows the site six months after completion with established vegetation growth, which has helped to protect the banks and to prevent against any future natural channel adjustment from destabilising the area.

Immediately after completion

After 6 months – Bank recovery

We returned to the site one year following the project to ensure that recovery was well underway, the following pictures show how well the area had recovered.

One year on – Showing the vertical stem growth on the willow spiling

One year on – Nag matting on the willow spiling