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Friston Surface Water Flood Study

Surface water flood modelling study to determine baseline flood risk through a rural village which is located downstream of a proposed Power Company development site.

Suffolk County Council

Background:

Suffolk County Council required a more thorough assessment demonstrating a clear understanding of the flooding mechanisms within the catchment. There was a known history of surface water flooding with an event captured in October 2019. BMT were able to complete a thorough site investigation and verify the hydraulic model with the October 2019 rainfall provided by the Environment Agency. Whilst there was little flood risk to properties in the catchment and therefore limited funding opportunities for flood schemes, low cost mitigation measures were presented which would offer respite to the village whilst informing the power company of the existing flood risk downstream of their site. This was key information to enable the power company to design drainage accordingly which in collaboration with Suffolk County Council might address existing flood risk as part of the development.

Outcomes and Benefits:

A high resolution surface water flood model was created and verified to offer detailed insight into flooding mechanisms within the catchment. Up to date hydrological methodologies were used to generate rainfall inputs to the model which were calibrated for initial conditions based on observed rainfall datasets. Do Nothing and mitigation scenarios were completed to the understand potential economic benefits or any scheme. The proposed mitigation measures include flood attenuation basins and bunds, Natural Flood Management measures and Property Level Protection. The information has been used to identify locations along with potential costs and benefits for flood mitigation schemes. Detailed mapping of maximum flood depths, hazard and velocity were created. We continue to advise Suffolk County Council throughout the project offering technical advice and expert quality assurance of any outputs from the power company relating to drainage proposals for the new development site.

 Services and Expertise Provided:

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