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[email protected] www.haycock-associates.co.uk Lower River Otter: Long term options for drainage and flood management Client Clinton Devon Estates Author Dr. N.E. Haycock Date 18th December 2009 updated 16th February 2010 Version 3 rivers soils hydrology landscapes Haycock Associates Limited. Registered in England No. 03934665 VAT No. GB 658 1644 14 Registered office: Red Roof, Wick Road, Little Comberton, Pershore, Worcestershire WR10 3EG. Haycock Table of Contents Executive Summary 1 Aims of the Report 2 Introduction 2 Background 4 Catchment Topography and Geology 4 Lower Otter Topography and Geology 6 Catchment Hydrology 8 Current Drainage Layout 10 Recorded Flood Events 12 Tidal Levels and Data and its Current Influence 16 Historical Periods and Accounts of the Lower Otter Valley 18 Hydraulic Model of the Lower Otter Valley 20 Flood Dynamics - Fluvial 20 Flood Dynamics - Tidal 25 Flood Dynamics - Drainage 29 Predicted Sea Level and Flood Regime 29 Conclusions Arising from the Simulation Flood Models. 30 Long Term Options for Drainage and Flood Management 31 Option A - Cricket Ground Bund 32 Option B - Relocation of Cricket Ground 34 Haycock Option C - South Farm Road 35 Option D - River Otter floodplain at White Bridge. 37 Option E - Southern Big Marsh (linked to option B, C and D). 38 Option F - Northern Big Marsh 40 Option K - River Otter Big Bank Reach 42 Option G - Little Bank and Swale 43 Option H - Otterton Mill and Otterton Bridge 44 Summary of Options - Table 5 47 Overview and recommendations 48 Key Documentation 49 Appendix A: Long section through the Lime Kiln Culvert (Howick and Partners, 2001).