Strategic Flood Risk Assessment - South Worcestershire ...

Estimated Attenuation Storage Volume (m 3 ) 246 – 344SUDS and the development site:1 in 100 year (plus climate change) 34.5SUDS TypeSource ControlInfiltrationDetentionFiltrationConveyancePotentialSuitabilityCommentsAll forms of source control excluding previous pavements would besuitableMapping suggests underlying soil is likely to be permeable.However, the high risk of groundwater flooding would makeinfiltration unsuitableMapping suggests that site slopes are steep and detention storage‘above ground’ may therefore not be viableMapping suggests that filtrations would be suitable but require a formof liner to prevent ingress of groundwater into the SUDS systemMapping suggests that site slopes would be suitable for conveyance.However, due to the steepness of slope may require check dams toslow flowsThe site is not located within a groundwater source protection zone.Mixed use developments should provide at least two independent SUDS features inseries to provide a suitable level of water quality treatment.Flood Defences:None.Effects of Climate Change:Increased water levels in the Laughern Brook. Increased rainfall intensities.Flood Risk Implications for Development:All development should be located within Flood Zone 1, unless appropriate inaccordance with NPPF Technical Guidance. As such, there is limited scope fordevelopment at this site.A detailed site-specific flood risk assessment, including hazard mapping, will berequired for any development in Flood Zone 2, or for sites greater than 1ha in FloodZone 1.The site is not suitable for residential development.Resilience measures will be required if buildings are situated in the flood risk area.Green infrastructure should be considered within the mitigation measures for surfacewater runoff from potential development.Assessment for runoff should include allowance for climate change effects.New or re-development should adopt exemplar source control SUDS techniques toreduce the risk of frequent low impact flooding due to post-development runoff.The site falls within an area indicated to potentially be susceptible to groundwateremergence. Further assessment of groundwater risk would be required and anassessment of suitable surface water mitigation techniques should be made at thedetailed FRA level.Onsite attenuation schemes would need to be tested against the hydrograph of thereceiving watercourse to ensure flows are not exacerbated downstream within thecatchment.The A44 Bromyard road, the current and only access road to the site is at risk fromboth fluvial flooding and surface water. Suitable alternative access arrangementsaway from the floodplain will need to be investigated further.Demonstration that development at this location can be made safe.2012s5947 S Worcestershire Level 2 SFRA Update FINAL Report v1.0.doc 67