construction and refurbishment of earthen irrigation channel banks

ProtectiveCoverMaterialGravel Refer Specification,section 17.5.1.Sand Refer Specification,section 17.5.2.TopsoilwithVegetationCoverChemicaltreatment ofmaterialavailable onsiteRefer Specification,section 17.5.3.The addition of lime,gypsum, and/or fertiliserto improve the soilstructure and chemicalcomposition.Application Advantages Disadvantages Notes1. Provides stable, long-lastingprotection.2. Useful if crest is to be used asan access track1. May allow vegetation growth.2. River sand is often readilyavailable near irrigation areas.Normally obtainable from newchannel site or borrow pit.Can use excess material whichmight otherwise have to bedisposed of.Can be expensive if a suitablematerial is not available locallyMay be washed or blown away if novegetation is established.1. Not suitable for crest where it isto be an access track.2. Treatment is limited to certainperiods of the year when grassescan be successfully established.3. Mineral status of the soil may notbe adequate for vigorous growth.4. Growth can be stunted by lack ofmoisture.5. Slashing or vegetation controlmay be required1. Cost2. Difficult to mix well on-site.In G-MW in Victoria, acrushed rock containingcalcium carbonate is usedwhich reduces crackingand dispersion in mediumto heavy claysNeed a suitable climate togrow grass all year.Table 17-1 Protective Cover MaterialsConstruction and Refurbishment of Earthen Channel Banks August 2002 – Edition 1.0 17-4