Strategic Flood Risk Assessment - South Worcestershire ...

SUDS and the development site:SUDS TypeSource ControlInfiltrationDetentionFiltrationPotentialSuitabilityCommentsAll source control techniques are likely to be suitableMapping suggests low permeability at this site, site investigationshould be carried out to assess potential for drainage by infiltrationDetention 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 viableAll filtration techniques are likely to be suitableConveyanceFlood Defences:None.All 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 SUDS features inseries to provide a suitable level of water quality treatment.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.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.Development of the site is proposed to focus on residential uses.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.Onsite attenuation schemes would need to be tested against the hydrograph of thereceiving watercourse to ensure flows are not exacerbated downstream within thecatchment.The site falls within an area highly susceptible to groundwater emergence (>25-50%). An assessment of suitable surface water mitigation techniques should bemade.The main access road to the site, Boat Lane, is at risk from both fluvial flooding andsurface water. Suitable alternative access arrangements away from the floodplainwill need to be investigated further.Demonstration that development at this location can be made safe2012s5947 S Worcestershire Level 2 SFRA Update FINAL Report v1.0.doc 51