The village of Riseley, part of the Kym Catchment in Bedfordshire, has a history of flooding. The primary sources of flooding in the village are from high intensity summer storms causing rapid surface water runoff and accumulation, as well as rapid fluvial flooding when the Riseley Brook bursts its banks. Located as it is, immediately upstream of Riseley Village, the Mallowry is well placed to provide flood relief for the village. The Mallowry is a beautiful Edwardian property, situated on approximately 35 acres of gardens and grounds. The existing land uses are grazed agricultural land, with some small woodland and shrubs close to the river.
We were appointed to undertake a flood modelling study of the catchment and develop a feasible, low cost and Natural Flood Management (NFM) orientated flood relief scheme on the property. The requirements of the client were to have a tangible positive impact on flood risk in the downstream village, whilst also providing improvements to the morphology and ecology of both the channel and immediate flood plain. The design should work for a range of extreme events, considering the 2 year, 30 year and the 100 year specifically. The project required our team to develop and maintain strong relationships with key stakeholders in order to develop the flood relief strategy.
WHAT WE DID:
STRATEGIC PLANNING / POLICY STAGE
- Flood Relief Strategy
- Natural Flood Management Advice
- Hydraulic Modelling using TUFLOW
KEY ACHIEVEMENTS / BENEFITS
- We were able to build a suitably detailed, but highly dynamic, hydraulic model of the catchment that both well represented the catchment surface flow paths and was able to rapidly run multiple design proposals. The modelling was undertaken in TUFLOW, making use of the latest Sub Grid Sampling tools to improve surface flows, and was approved in terms of methodology by the key regulatory bodies. We were able to introduce various elements of the NFM tool box to the model, including; leaky dams, flood plain planting and offline storage areas testing the impact of each element individually and refining a final combination of the approaches that met the requirements of the client as well as key stakeholders.