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construction and refurbishment of earthen irrigation channel banks

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12. Earthen Channel DesignTable <strong>of</strong> ContentsSubjectPage No.12.1 Introduction.............................................................................................................. 12-312.2 Scope........................................................................................................................ 12-312.3 Required Life ........................................................................................................... 12-312.4 Life-Cycle Cost Considerations ............................................................................... 12-412.5 Objectives in Design................................................................................................ 12-412.6 Design Procedure ..................................................................................................... 12-512.7 Site Survey............................................................................................................... 12-712.8 Geotechnical Investigation....................................................................................... 12-712.9 Estimation <strong>of</strong> Earthworks Volumes......................................................................... 12-912.10 Hydraulic Considerations....................................................................................... 12-1012.10.1 Types <strong>of</strong> Open Channel Flow....................................................................................................... 12-1012.10.2 Channel Cross Section.................................................................................................................. 12-1112.11 Channel Velocity.................................................................................................... 12-1212.11.1 Manning’s n – Co-efficient <strong>of</strong> Roughness .................................................................................... 12-1312.11.2 Permissible Velocities .................................................................................................................. 12-1512.11.3 Maximum Velocities .................................................................................................................... 12-1612.11.4 Additional Protection against Erosion .......................................................................................... 12-1812.11.5 Minimum Velocities ..................................................................................................................... 12-1912.12 Channel Control..................................................................................................... 12-2012.12.1 Upstream Control ......................................................................................................................... 12-2212.12.1.1 Design Discharge Level........................................................................................................ 12-2212.12.1.2 Maximum Water Level......................................................................................................... 12-2312.12.1.3 Best Practice......................................................................................................................... 12-2412.13 Freeboard ............................................................................................................... 12-2412.13.1 Purpose <strong>and</strong> Philosophy................................................................................................................ 12-2412.13.2 Channel Maintenance ................................................................................................................... 12-2612.13.3 Past Practice ................................................................................................................................. 12-2612.13.4 Wind <strong>and</strong> Wave Action ................................................................................................................ 12-2612.13.4.1 Determination <strong>of</strong> the Setup (Wind tide)................................................................................ 12-2712.13.4.2 Determination <strong>of</strong> Wave Height............................................................................................. 12-2712.13.4.3 Freeboard for Wave Height .................................................................................................. 12-2812.13.4.4 Determination <strong>of</strong> Wave Runup ............................................................................................. 12-2912.13.4.5 Methods to Reduce Wave Runup ......................................................................................... 12-2912.13.4.6 Batter Protection................................................................................................................... 12-2912.13.4.7 Change <strong>of</strong> Alignment............................................................................................................ 12-3012.13.5 Minimum Freeboard Allowance ................................................................................................... 12-3012.13.6 Risk Approach.............................................................................................................................. 12-3012.13.7 Determination <strong>of</strong> Freeboard Allowance........................................................................................ 12-3012.13.8 Construction Notes ....................................................................................................................... 12-3112.13.9 Operation Notes............................................................................................................................ 12-3112.13.10 Unauthorised interference............................................................................................................. 12-3112.14 Longitudinal Sections ............................................................................................ 12-31Construction <strong>and</strong> Refurbishment <strong>of</strong> Earthen Channel Banks August 2002 - Edition 1.0 12-1

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