Chapter 9: Road drainage and the water environment

Contents
1 Introduction 1
1.1 Overview 1
1.2 Proposed Development Details 1
1.3 Previous FRA’s 2
2 Policy Review 3
2.1 Planning Context 3
2.2 Planning Policy Statement 25 (PPS25) 3
2.3 Harborough Strategic Flood Risk Assessment 5
3 Flood Risk to the Proposed Development 7
3.1 Fluvial Flooding – Main River 7
3.2 Fluvial Flooding – Ordinary Watercourses (Non-Main River) 9
3.3 Coastal and Tidally Influenced Flooding 9
3.4 Groundwater Flooding 9
3.5 Surface Water Runoff 10
3.6 Flooding from Artificial Drainage Systems 12
3.7 Flooding from Infrastructure Failure 13
3.8 Climate Change 14
3.9 Summary of Risks to Site 15
4 Impacts of the Proposed Development on Flood Risk
Elsewhere 17
4.1 Impacts on Fluvial Flood Risk 17
4.2 Impacts on Groundwater Flooding 17
4.3 Impacts on Flood Risk from Surface Water Runoff 18
4.4 Impacts on Flooding from Artificial Drainage Systems 18
4.5 Impacts on Flooding from Infrastructure Failure 18
4.6 Summary of Flood Impacts from Development 19
5 Proposed Mitigation Measures 20
5.1 Mitigation of Impacts on Fluvial Flooding 21
5.2 Mitigation of Groundwater Flood Risks 22
5.3 Mitigation of Surface Water Runoff (Overland Flows) 23
5.4 Mitigation of Flood Risks from Artificial Drainage Systems 23
5.5 Mitigation of Flood Risks from Infrastructure Failure 24
5.6 Incidental Mitigation Measures 24
5.7 Summary of Recommended Mitigation Measures 25
6 Residual Risks 27
7 PPS25 Sequential and Exception Test 29
7.1 The Sequential Test 29
7.2 The Exception Test 29
7.3 Summary 30
8 Conclusion 31