Conwy Flood Alleviation and Spillway Scheme

Salix supplied 9000m² of VMax³ Shear Stress Turf as part of the Conwy Flood Alleviation Scheme in September 2009. Just two months later the area experienced the worst flooding in 25 years of recording with floods exceeding the 1:30 year events of 2004/2005.

Flooding in Llanrwst and Trefriw occurred in February 2004 and January 2005 affecting many properties. Sections of flood embankment were in poor condition and had breached on a number of occasions.

The £7 million project was developed to allow the natural flood plain to protect 96 homes and businesses in Llanrwst and Trefriw.  The area is prone to flooding as it drains rain from the mountains in eastern Snowdonia.

It allows water to flow over man-made flood banks onto the natural flood plain of the valley floor, where it is then stored and drains away over a few days. To allow for this, the flood bank immediately upstream was lowered and a new flood bank built to protect homes in Trefriw.

The VMax³ Shear Stress Turf using P550 was contract grown with a specified grass mixture to provide instant vegetative erosion protection on the lowered flood defences.

P550 within the turf offers permanent turf reinforcement, increasing the power of vegetation to withstand high velocity flow regimes of up to 7.6m/sec.

The Shear Stress Turf on the spillway was successfully put the test when the area was hit by heavy rain just two months later in November 2009.

All parties concerned were impressed with the performance of the product, with Team Van Oord Project Manager Matt Phillips stating

“The pre grown P550 performed very well during a significant flood event. There was no flood damage to repair on the banks protected by the P550”.