Strategic Flood Risk Assessment - South Worcestershire ...

Estimated Attenuation Storage Volume (m 3 ) 180-272.5SUDS and the development site:SUDS TypePotentialSuitabilityCommentsSource ControlInfiltrationDetentionFiltrationConveyanceMost source control techniques are likely to be suitable. Permeablepaving is unlikely to be suitable due to high risk of groundwaterfloodingMapping suggests underlying soil is likely to be permeable.However, the high risk of groundwater flooding would makeinfiltration unsuitableDetention techniques may be suitable if a non-permeable liner isprovided to prevent the ingress of groundwater. Mapping suggeststhat site slopes may be steep so larger features may not be viableFiltration techniques may be suitable if a non-permeable liner isprovided to prevent the ingress of groundwaterAll conveyance techniques are likely to be suitableThis site is located within a flooding hotspot so all efforts should be made tominimise the rate and volume of runoff leaving the site.The site is not located within a groundwater source protection zone.Residential developments should provide at least two independent SUDSfeatures in series to provide a suitable level of water quality treatment.Flood Defences:None.Effects of Climate Change:Increased rainfall intensity. Increased water levels in the River Avon.Flood Risk Implications for Development:All development should be located within Flood Zone 1, unless appropriate inaccordance with NPPF Technical Guidance.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 inFlood Zone 1.Development of the site is proposed to focus on residential uses.Resilience measures will be required if buildings are situated in the flood riskarea.Green infrastructure should be considered within the mitigation measures forsurface water runoff from potential development.Assessment for runoff should include allowance for climate change effects.New or re-development should adopt exemplar source control SUDStechniques to reduce the risk of frequent low impact flooding due to postdevelopmentrunoff.Onsite attenuation schemes would need to be tested against the hydrograph ofthe receiving watercourse to ensure flows are not exacerbated downstreamwithin the catchment.The site falls within an area indicated to potentially be susceptible togroundwater emergence. Further assessment of groundwater risk would berequired and an assessment of suitable surface water mitigation techniquesshould be made at the detailed FRA level.The B4084 High Street road and King George's Way, the main access roads tothe site, are at risk from fluvial flooding and \ or surface water. Suitablealternative access arrangements away from the floodplain will need to beinvestigated further.Demonstration that development at this location can be made safe.2012s5947 S Worcestershire Level 2 SFRA Update FINAL Report v1.0.doc 134