Strategic Flood Risk Assessment - South Worcestershire ...

Estimated Attenuation Storage Volume (m 3 ) 34 – 46SUDS and the development site:1 in 100 year (plus climate change) 27.6SUDS TypeSource ControlInfiltrationDetentionFiltrationConveyancePotentialSuitabilityCommentsAll forms of source control are likely to be suitableMapping 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 viableAll forms of filtration are likely to be suitableMapping suggests that site slopes would be suitable for conveyance.However, due to the steepness of slope may require check dams toslow flowsFlood Defences:None.This 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 SUDS featuresin series to provide a suitable level of water quality treatment.Effects of Climate Change:Increased rainfall intensities.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 in FloodZone 1.Redevelopment or alternative use of the site is proposed to focus on residentialuses.Resilience measures will be required if buildings are situated in the flood risk area.Green infrastructure should be considered within the mitigation measures forsurface water runoff from potential developmentAssessment for runoff should include allowance for climate change effectsNew 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 current and only access road to the site, the Hampton Road, is at risk from bothfluvial flooding and surface water. Suitable alternative access arrangements awayfrom 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 104