Conder Developments Ltd Proposed Development High Street Rocester Staffordshire Flood Risk Assessment Prepared by EWE Associates Ltd Final Report RevE February 2014 EWE Associates Ltd Windy Ridge Barn Thealby Lane Winterton Scunthorpe North Lincolnshire DN15 9TG t: 0845 8377783 M: 07875 972270 e: lea.favill@eweassociates.com This document has been prepared solely as a Flood Risk Assessment for Conder Developments Ltd. EWE Associates Ltd accepts no responsibility or liability for any use that is made of this document other than by the Client for the purposes for which it was originally commissioned and prepared. Conder Developments Ltd Proposed Development, High Street, Rocester – Flood Risk Assessment Final Report RevE February 2014 REVISION HISTORY Revision Ref./ Amendments Issued to Date Issued Draft Report Rev A: 8th November 2008 Paul Shanley (Conder Developments Ltd) - 1No. Copy Draft Report Rev B: 24th November 2008 Amendments following Client’s Paul Shanley (Conder Developments comments Ltd) - 1No. Copy Environment Agency - 1No. Copy Final Report Rev C: 13th February 2012 Amendments to layout drawing Paul Shanley (Conder Developments Ltd) - 1No. Copy Pegasus Planning - 1No. Copy Final Report Rev D: 30th August 2012 Updated with latest EA flood data and Paul Shanley (Conder Developments subsequent revision of flood envelopes Ltd) - 1No. Copy within site. Pegasus Planning - 1No. Copy New EA reservoir maps added and commented. Further local historical information added. Final Report Rev E: 13th February 2014 Updated with latest EA flood data and Paul Shanley (Conder Developments subsequent revision of flood envelopes Ltd) - 1No. Copy within site. Pegasus Planning - 1No. Copy Updated drainage strategy CONTRACT This report describes work commissioned by Conder Developments Ltd following instruction by their representative on 4th August 2008. Conder Development Ltd representative for the contract was Mr Paul Shanley. Donna Metcalf and Lea Favill of EWE Associates Ltd carried out the work. Date: 13th February 2014 Prepared by: ………………………………… ………………… Lea Favill Director EWE Associates Ltd Windy Ridge Barn, Thealby Lane, Winterton, Scunthorpe, North Lincolnshire DN15 9TG. t: 01724 733349 : i Conder Developments Ltd Proposed Development, High Street, Rocester – Flood Risk Assessment Final Report RevE February 2014 EXECUTIVE SUMMARY Executive Summary The site presently consists of farmland divided into a number of fields separated by established hedgerow and fence lines, attached to Churnet House Farm, located off High Street in the Staffordshire village of Rocester. Churnet House Farm and associated outbuildings occupy the area of the site to the north, with the remaining undeveloped area within the site, previously utilised as pasture for grazing cattle and horses. The parcels of land are linked by an unsurfaced track leading south from the farm buildings off High Street. The site is located 15 miles to the south east of Stoke on Trent. The site covers a total area of 4.0 Hectares. It is considered that the existing site is 90% permeable due to the relatively small roof and paved areas within the site. During the day of the site visit there was evidence of a positive surface water drainage system within farm building complex via rainwater pipes and yard gullies. The remaining farmland area is not positively drained. The site lies at levels between 84.80mAOD along the south boundary of the development area, and 86.63mAOD within the farm building complex. There are existing residential dwellings to the north along Churnet Row, and also to east of the site within Rocester village. JCB’s World Headquarters site is located 300m to the north west of the proposed development, and JCB Finance is located at The Mill, which is situated immediately adjacent to the west boundary of the site. The proposed development is to comprise mixed development comprising residential units and an employment area covering a total of 2.14 Hectares. It is anticipated that the impermeable area of the site will be increased to 53% following completion of the development. The development site is shown to lie partially within Zone 3 of the Environment Agency Flood Map (version 2.8.2), being the zone with risk of 1 in 100 year (1% AEP) or greater for river flooding. The remaining area of the site lies within Zone 2 of the Environment Agency Flood Map (version 2.8.2), being between a 1 in 100 and 1 in 1,000 annual probability (chance) of river flooding (1% -0.1%). It is understood that the flood zone plan provided by the Environment Agency has been mapped using LIDAR, and indicates that the primary flood risk to the site comes from the River Churnet. The watercourse is situated approximately 40m to the west of the proposed development. The development site is larger than 1 hectare in size. There are three sources of flood risk – the River Churnet; the River Dove and surface water runoff – it is necessary to determine flood water levels at the site for the desired return periods emanating from these sources. The River Churnet is in line with the development and is considered to represent the greatest flood risk to the site. The River Churnet estimated 1 in 100 year flood levels are 84.62mOD, 84.90mOD and 85.81mOD at Node References 02682, 02888u and 02945u respectively. The estimated 1 in 100 year plus climate change flood levels at these nodes are 84.77mOD, 85.07mOD and 85.96mOD. From the topographic survey of the development, existing ground levels are shown to be elevated above these modelled flood levels. Following consultation with the Environment Agency it was suggested that the internal ground floor levels for the proposed residential development are set at a minimum of 600mm above the 1 in 100 year plus climate change flood levels in line with the site. It is also advised that the internal ground floor level for the commercial development within the employment area is set at a minimum of 300mm above the 1 in 100 year plus climate change flood level, incorporating flood resilience measures up to 300mm above the ground floor level of the proposed buildings. For the purposes of recommending finished ground floor levels within the area of the site set aside for residential development, the area has been divided into three sections corresponding to the locations of node references 02682, 02888u and 02945u. In compliance with the Environment Agency’s requirements it is recommended that internal ground floor levels in line with Node Reference 02945u are set at a minimum of 86.560mOD. The lowest existing ground level within this area is shown to be 86.050mAOD and as such, some land/floor raising will be required, in order to provide adequate freeboard above the 1 in 100 year plus climate change flood level in line with the development. The internal ground floor level of the proposed residential units in line with Node Reference 02888u should be set to a minimum of 85.430mOD. The lowest existing ground level within this section of the site is 85.430mAOD and as such, no land/floor raising will be required. EWE Associates Ltd Windy Ridge Barn, Thealby Lane, Winterton, Scunthorpe, North Lincolnshire DN15 9TG. t: 01724 733349 : ii Conder Developments Ltd Proposed Development, High Street, Rocester – Flood Risk Assessment Final Report RevE February 2014 Additionally, it is recommended that the internal ground floor levels of the proposed dwellings in line with Node Reference 02682 are set to a minimum level of 85.110mAOD. The lowest existing ground level within this southern section of the proposed development has been surveyed as 84.800mAOD. Therefore some land/floor raising will also be required within this part of the development in order to provide adequate freeboard above the 1 in 100 year plus climate change flood level. In order to mitigate against localised flooding which may be caused by heavy rainfall, it is also advocated that the internal ground floor levels of the proposed residential units are elevated at least 150mm above the adjacent external finished ground levels. The area of the site set aside for commercial development is in line with Node Reference 02945u and therefore the 1 in 100 year plus climate change flood level utilised for this part of the development is estimated to be 85.96mOD. In compliance with the Environment Agency’s requirements it is recommended that internal ground floor levels in line with Node Reference 02945u are set at a minimum of 86.260mOD. The lowest existing ground level within this area is shown to be 86.050mAOD and as such, some land/floor raising will be required, in order to provide adequate freeboard above the 1 in 100 year plus climate change flood level in line with the development. For the low lying areas within the commercial site, where ground levels are less than 600mm above the 1 in 100 year plus climate change flood level, it is recommended that flood proofing measures are incorporated into the commercial building design up to a level of 600mm above the 1 in 100 year plus climate change flood level, at 86.56mOD. In order to mitigate against localised flooding which may be caused by heavy rainfall, it is also advocated that the internal ground floor levels of the proposed commercial units are elevated at least 150mm above the adjacent external finished ground levels. It is concluded that there is a low risk of flooding due to overtopping of the Rivers Dove and Churnet during the 1 in 100 year and 1 in 100 year plus climate change flood events within Rocester. An additional flood risk is from increased surface water runoff following development. The implementation of mitigation measures as described above will ensure that any risk of flooding at the proposed development may be reduced to an acceptable level.
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