Strategic Flood Risk Assessment - South Worcestershire ...

Estimated Attenuation Storage Volume (m 3 ) 1,292 – 1,789SUDS and the development site:SUDS TypePotentialSuitabilityComments1 in 100 year (plus climate change) 39.4Source ControlInfiltrationDetentionFiltrationConveyanceAll 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 the site slopes are steep and that detentionstorage ‘above ground’ would not be viableMapping suggests that filtrations would be suitable but require a formof liner to prevent ingress of groundwater into the SUDS systemAll forms of conveyance are likely to be suitableFlood 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 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, 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.Proposed for residential uses.Flood Zone 2 should be used as public open space.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 effectsNew 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 current and only access road to the site, Drakes Lea road, is at risk from fluvialflooding and surface. Suitable alternative access arrangements away from thefloodplain 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 113