Chapter 9: Road drainage and the water environment

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3.8 Climate Change The impacts of climate change are uncertain. Modelling carried out by the Hadley Centre (Met Office) has looked at a number of different scenarios. These models suggest that winters will become wetter over the whole of the UK, by as much as 20 per cent by the 2050’s. A shift in the seasonal pattern of rainfall is also expected, with summer and autumn becoming much drier than at present. However, the intensity of the rainfall during summer storms is predicted to be much greater. So even though the overall amount of rain in the summer will be less, there will be more occurrences of heavy rainfall. Once constructed, the development is expected to be there for at least 100 years. (This is generally considered an appropriate time horizon for Developers to have to accommodate.) However, once an area has become developed, it is more likely to remain developed in some form or another beyond this life-span. This should be taken into account in longer-term strategies for the area. Therefore, climate change will present a Future Risk to the site in the form of greater volumes of surface water runoff from the surrounding area and from the site itself. In making an assessment of the impacts of climate change Table 5 shows the precautionary allowances that should be considered for the parameters relevant to this site. Parameter 1990 to 2025 2025 to 2055 2055 to 2085 2085 to 2115 Peak rainfall intensity +5% +10% +20% +30% Peak river flow +10% +20% Table 5: Recommended national precautionary sensitivity ranges 4 4 PPS25 – Table B2 14
3.9 Summary of Risks to Site Table 6 contains a summary of the risks to the site. Mitigation measures to address identified risks are discussed in Section 0. Flood Risk Level of Risk Actions Required 5 A14 Embankments Low None Fluvial - Main River Highways Low None Bridleway Crossing Fluvial – Ordinary Watercourse Sea/Tidal High Low None identified Mitigation measures Ensure culvert capacities are assessed/designed based on DMRB methodology. None Groundwater Medium Mitigation measures Surface Water Runoff Low Mitigation measures Artificial Drainage Systems Potentially High Further investigation – visual assessment planned by drainage design team. Infrastructure Failure Low None Table 6: Summary of risks to the M1 Junction 19 5 See Section 5 for further details. 15
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M1 Junction 19 Improvement Environm
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M1 JUNCTION 19 IMPROVEMENT ENVIRONM
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Page 50 and 51: M1 JUNCTION 19 IMPROVEMENT ENVIRONM
Page 71 and 72: Appendix A - Pollution and Spillage
Page 73: Method D - Assessment of Pollution
Page 78 and 79: Groundwater: Hydrocarbons Hydrogeol
Page 83 and 84: Non Technical Summary Skanska Const
Page 85 and 86: Contents 1 Introduction 1 1.1 Overv
Page 87 and 88: 1 Introduction 1.1 Overview Jacobs
Page 89 and 90: 2 Policy Review 2.1 Planning Contex
Page 91 and 92: When the both the ‘Flood Zone’
Page 93 and 94: 3 Flood Risk to the Proposed Develo
Page 95 and 96: 3.2 Fluvial Flooding - Ordinary Wat
Page 97 and 98: Major earthworks affecting surface
Page 99: 3.7 Flooding from Infrastructure Fa
Page 103 and 104: 4 Impacts of the Proposed Developme
Page 105 and 106: 4.6 Summary of Flood Impacts from D
Page 107 and 108: 5 Proposed Mitigation Measures 5.1
Page 109 and 110: The extents of this problem are cur
Page 111 and 112: 5.7 Summary of Recommended Mitigati
Page 113 and 114: 6 Residual Risks The level of flood
Page 115 and 116: 7 PPS25 Sequential and Exception Te
Page 117 and 118: 8 Conclusion The M1 Junction 19 Imp
Page 119 and 120: Appendix A Existing Layout, Environ
Page 127 and 128: Appendix B Contractor’s Proposals
Page 129 and 130: Appendix C Hydrogeological Assessme
Page 131 and 132: Memorandum Fairbairn House, Ashton
Page 133 and 134: Memorandum (Continued) Page 3 of 6
Page 135 and 136: Memorandum (Continued) Page 5 of 6
Page 141 and 142: Appendix D Volume Distribution for
Page 143 and 144: Floodplain compensation area - elev
Page 145: Depth Bands (m) TOTAL (m³) Area Re
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Chapter 9: Road drainage and the water environment

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