Strategic Flood Risk Assessment - South Worcestershire ...

Surface water presents a risk to the site. Further development and creation ofimpermeable surfaces may result in an increase of surface water flood risk. TaylorsLane, Norton Road and Church Lane, some of the main access roads within the sitearea are at risk from surface water.Surface Water Drainage:As an indication of requirements to manage surface water runoff at the development site anassessment of the soil types, greenfield runoff rate and attenuation storage volume is includedbelow. Storage volumes displayed are calculated with an assumption that 75% of the site willbe developed impermeable ground. A 25% increase in rainfall depths has been included torepresent predicted future climate change effects.PLEASE NOTE: This assessment has been carried out using broad-scale datasets and aims toprovide an indication of the likely opportunities and constraints for this development site. Adetailed drainage assessment based on site-specific conditions should be carried out by asuitably qualified professional and submitted with any planning application. The values belowshould not be used for design purposes.Soil TypeGreenfield Runoff Rate (l/s/ha)Unknown – Lower PermeabilityEstimated Attenuation Storage Volume (m 3 ) 93,613 – 137,332SUDS and the development site:1 in 2 year 4.31 in 100 year (plus climate change) 16.4SUDS TypeSource ControlInfiltrationDetentionFiltrationConveyancePotentialSuitabilityCommentsAll forms of source controls are likely to be suitableMapping suggests high permeability at this site, site investigationsshould be carried out to assess potential for drainage by infiltrationMapping suggests that site slopes are steep and therefore somelarger features ‘above ground’ may not be viableAll forms of filtration are likely to be suitableAll forms of conveyance 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.Mixed use developments should provide at least two independent SUDS features inseries to provide a suitable level of water quality treatment.Flood Defences:Kempsey flood defences.Effects of Climate Change:Increased rainfall intensities. Increased water levels in the Hatfield Brook, the unnamedtributary of the Hatfield Brook and the River Severn.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 residential,leisure, commercial and recreational mixed use proposals.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 development.Assessment for runoff should include allowance for climate change effects.2012s5947 S Worcestershire Level 2 SFRA Update FINAL Report v1.0.doc 88