construction and refurbishment of earthen irrigation channel banks

Causes ofSpecific factorDeteriorationChannel • Design Standarddesign • Shape of channel cross-section• Depth, width and capacity ofchannel waterway• Bank height above naturalsurface• Bends• Channel reach length• Orientation of channel in relationto prevailing winds• Meander formationBank material • Soil type• Bank Cracking• Bank heaving and slumping• PipingConstruction • Construction technique• Construction quality control• Adjacent borrow pitsOperation• Degree of operationalsupervision• Operational practices of ControlStructures• Water level fluctuations• Channels running above designoperating level• Overtopping of banks• High water velocities• Turbulence at structures andbends• Channel filling and drawdown• Operational vehicle traffic on topof banksCauses of Specific factorDeteriorationMaintenance • Over-excavation andsteepening of batter slopes• Core-Trenching• Vegetation and weed growth• Weed control techniques• Adjacent trees• Siltation• Inadequate MaintenanceLevelsStock andverminAdjacentlandholders• Stock Access, ie. cattle• Fencing• Carp• Yabbies/fresh water crayfish• Vermin and control techniques• Impact of adjacent farmingpractices on the bank• Farm vehicle traffic on bankEnvironment • Wind/wave action• Rainfall• Channel water qualityTable 10-1Causes of Channel Bank Deterioration10.1.2 Channel designThe channel design standard has a large impact on the life of channel banks. Aninadequate design can allow the banks to be subject to a high rate of deteriorationwith a subsequent reduction in channel bank life.10.1.2.1 Design StandardThe design standard of a channel bank will vary according to the design life of anirrigation scheme. Generally private schemes have a short design life (20-30years) with a low capital cost but higher annual maintenance costs.Construction and Refurbishment of Earthen Channel Banks August 2002 - Edition 1.0 10-4