WOKINGHAM BOROUGH COUNCIL FLOOD INVESTIGATION REPORTS WINTER 2013/2014 JANUARY 2016 ii WOKINGHAM BOROUGH COUNCIL FLOOD INVESTIGATION REPORTS WINTER 2013/2014 Wokingham Borough Council January 2016 – WSP | Parsons Brinckerhoff Mountbatten House Basing View Basingstoke RG21 4HJ Tel: +44(0) 1256 318 800 Fax: +44 (0) 1256 318 700 www.wspgroup.com www.pbworld.com Wokingham Borough Council Flood Investigation Reports WSP | Parsons Brinckerhoff Wokingham Borough Council Project No 70007120 January 2016 iii TABLE OF CONTENTS 1 EXECUTIVE SUMMARY ..............................................................1 2 INTRODUCTION ...........................................................................2 3 FLOOD RISK MANAGEMENT ROLES AND RESPONSIBILITIES .....................................................................6 4 TYPES OF FLOODING ................................................................7 5 INVESTIGATIONS ........................................................................9 6 RECOMMENDATIONS ............................................................... 11 7 ARBORFIELD ............................................................................. 13 8 SWALLOWFIELD ....................................................................... 18 9 SHINFIELD ................................................................................. 23 10 CHARVIL .................................................................................... 27 11 HURST ........................................................................................ 31 12 WARGRAVE ............................................................................... 37 GLOSSARY OF TERMS AND CONDITIONS ........................................... 43 Wokingham Borough Council Flood Investigation Reports WSP | Parsons Brinckerhoff Wokingham Borough Council Project No 70007120 January 2016 iv TABLE S TABLE 1-1 PARISH CONTACT DETAILS ............................................................. 9 TABLE 1-2 IMPACT OF FLOODING IN EACH PARISH...................................... 10 FIGURES FIGURE 1-1 FIGURE 70007120/1/101: WOKINGHAM BOROUGH MAIN RIVER AND ORDINARY WATERCOURSE NETWORK .................... 4 FIGURE 1-2 FIGURE 70007120/1/102: TOTAL NUMBER OF INTERNALLY FLOODED PROPERTIES BY PARISH ............................................... 5 APPENDICES A P P E N D I X A DRAWINGS APPENDIX A-1 ARBORFIELD – DRAWING NO. 70007120/01/101 APPENDIX A-2 SWALLOWFIELD – DRAWING NO. 70007120/02/101 APPENDIX A-3 SHINFIELD – DRAWING NO. 70007120/03/101 APPENDIX A-4 CHARVIL DRAWING NO. 70007120/04/101 AND 70007120/04/102 APPENDIX A-5 HURST – DRAWING NO. 70007120/05/101 AND 70007120/05/102 APPENDIX A-6 WARGRAVE – DRAWING NO. 70007120/06/101 AND 70007120/06/102 Wokingham Borough Council Flood Investigation Reports WSP | Parsons Brinckerhoff Wokingham Borough Council Project No 70007120 January 2016 1 EXECUTIVE SUMMARY The flood event of winter 2013/14 covers the period from mid-December 2013 to early March 2014, during which time a number of areas in Wokingham Borough were affected by flooding as a result of prolonged, persistent and heavy rainfall. The scale and magnitude of the majority of the flooding could not have been predicted. This report provides an investigation into the causes, mechanisms, consequences and responses associated with flooding in each of the affected areas within Wokingham Borough. Between the beginning of September and the end of November 2014 research was undertaken across the borough, comprising interviews with Flood Wardens, Parish and Town Council representatives and affected residents, site surveys and analysis of data gathered by Wokingham Borough Council during the floods. This research has enabled the production of a series of individual parish reports and maps, depicting the flooding experienced by each of the affected settlements in Wokingham Borough during the winter 2013/14 flood event. The supporting maps illustrate the affected properties, the approximate flood extents and the directions flood flows took through the town, village and / or parish. The information obtained from this investigation has highlighted the need for the initiation of a number of general, borough-wide measures. These requirements range from better targeted and more regular maintenance of both public and private drainage systems, to gathering data on the condition of features and structures which help prevent flooding. A series of location-specific recommendations have also been proposed to help mitigate the impact of future flooding in each town and village. The recommendations cut across all flood risk management authorities, with the responsibility for delivery of each measure shown within the report. Lessons have been learnt and Wokingham Borough Council is committed to ensuring work that communities are better able to mitigate and cope with future flood events. Wokingham Borough Council Flood Investigation Reports WSP | Parsons Brinckerhoff Wokingham Borough Council Project No 70007120 January 2016 2 1 INTRODUCTION 1.1 BACKGROUND 1.1.1 During winter 2013/14 much of the country was battered with heavy rain and winds, resulting in wide scale flooding. For the most part of 2013 rainfall totals were slightly below the long term average. However, from mid-December a succession of deep Atlantic low pressure systems caused torrential rain and strong winds. This extreme weather was fuelled by a powerful jet stream, causing it to continue throughout January and February. Areas in the south-east of the country received almost 2.5 times the volume of rainfall than expected over an average winter period. For the country as a whole, the winter, from the beginning of December until the end of February, was the wettest recorded in the UK since records began in 1766. 1.1.2 Between the 13th December and Christmas Day the total rainfall across Wokingham was up to 100mm in places, resulting in the River Loddon and the River Blackwater bursting their banks. The River Thames did not burst its banks in December as there was still capacity in the river system at this time. 1.1.3 Several dry days between Christmas and New Year allowed river levels to subside. This was followed by a second period of heavy rainfall around New Year and the first week of 2014, with rainfall totals between the 30th December and the 8th January averaging 90mm. Levels on the River Loddon rose again on New Year’s Day but they did not exceed those reached over the Christmas period. Widespread property flooding was not repeated. 1.1.4 At the end of January, levels in the rivers began to slowly fall. However, heavy and sustained rainfall at the end of January and during the first week of February caused levels to rise once again. The unrelenting rainfall throughout January and February resulted in water levels on the Lower Thames reaching their highest level for more than 65 years. 1.1.5 The worst affected areas were those located close to the major rivers in the borough; the River Loddon, the River Thames and the River Blackwater. The river and groundwater levels in the catchments were high throughout the period. The repeated storms generated maximum levels on these rivers and other tributaries of the River Thames in Wokingham. This resulted in even more water being added to an already inundated Thames floodplain. The location of these rivers is illustrated in figure 70007120/1/101. 1.1.6 Figure 70007120/1/102 illustrates the areas affected by flooding during the winter 2013/14 flood event based on the total number of properties that suffered internal and/or external flooding across Wokingham. 1.2 PARISH FLOOD INVESTIGATION REPORTS 1.2.1 From a review of the reported flooding incidents a number of parishes were identified where property flooding had occurred. The Parish reports provide an account of how the flooding occurred, the impact of the flooding and potential measures to reduce the likelihood and/or impact of future flooding events. Wokingham Borough Council Flood Investigation Reports WSP | Parsons Brinckerhoff Wokingham Borough Council Project No 70007120 January 2016 3 1.2.2 It should be noted that much of the following record has depended upon anecdotal evidence from members of the public and potential solutions at this stage have been based upon site observations only. Prior to taking any recommendations forward, a feasibility study will be undertaken to verify the cause and effect of the flooding and the viability of solutions. For example, in cases where enlarging culverts has been discussed, this has been done in the context of relieving upstream flooding; no assessments have been made at this stage into the viability of these culverts (in terms of other services, ground conditions etc.) or into the downstream impacts of the resulting increased flow. In order to carry out works to erect or alter a culvert, consent from the Lead Local Flood Authority is required under Section 21 of the Land Drainage Act 1991. 1.2.3 The information contained in this document has been compiled for the guidance of Wokingham Borough Council Officers, as well as local residents, to provide information to the affected Parish Councils. Wokingham Borough Council does not accept any liability for any inaccuracies in the information contained in this document. Wokingham Borough Council Flood Investigation Reports WSP | Parsons Brinckerhoff Wokingham Borough Council Project No 70007120 January 2016 4 Figure 1-1 Figure 70007120/1/101: Wokingham Borough Main River and Ordinary Watercourse Network Wokingham Borough Council Flood