Context

Grass Concrete's Grasscrete permeable concrete paving system was selected to armour the slopes of a spillway leading to a flood storage bund for East Riding of Yorkshire Council's Pocklington Flood Alleviation Scheme. With a new housing development next door, there was a need to tone down the engineering impact.

Solution

The combination of flexible void formers and cast-in-place concrete, enabled contouring up to the crest beam to create a smooth, curved transition to aid flow efficiency. With a flow capability of 8m per second, the Grasscrete facing to the spillway allows overspill from the storage area to be collected in the stilling basin before its transfer to the adjacent beck.

Topsoil from the site strip was stockpiled ready to infill the Grasscrete pockets, enabling local pH values to be maintained. The level concrete surface enabled the soil to be bladed into the pockets. Swift grass growth was established alongside the ‘toned down’ green concrete.

Outcome

The flood bund created a barrier between the flood storage area and the open fields to Persimmon Homes’ new housing development.

Pocklington Flood Alleviation Scheme (POCFAS) is the latest flood prevention scheme introduced by the Council which, along with the other schemes, has collectively provided protection for up to 23,000 homes. Now complete, the storage area created by the bund is capable of holding 90,000m3 of flood water to mitigate the risk of downstream flooding in Pocklington town centre and its surrounding neighbourhoods.