construction and refurbishment of earthen irrigation channel banks

Aim for crest width ofabout 2 metres on smallerchannelsClay CoreMaterialEroded BankMaterial(EBM)Inside batterstabilisationwith EBMFigure 20.12Core filled with EBMThe success of core trenching is heavily dependent on the technique and thematerial used. Use of saturated EBM from the waterway should be avoided. ReferPhoto 20-8. The EBM should be let dry as much as possible. Also all vegetationand organic material should be removed from the EBM before placing in core.Photos\refurbishment\Cohuna channelsEBM7.jpgPhoto 20-8Saturated material used to fill core. On drying core cracks andbecomes crumblyPhotos\refurbishment\Cohuna channelsEBM6.jpgPhoto 20-9Cut through channel bank showing original compacted bank with layerof silt placed over the top20.5.3 Case StudyThe Torrumbarry 3/1 and 16/1 channels were rehabilitated during 1997 in thefollowing manner:• channels were selected according to the availability of EBM• already had enough freeboard so that any works would not bring this belownormal operating ranges.• Channel was drained. When water level had dropped, the topsoil was strippedand stockpiled.• Any hollows encountered in the batter were filled with good clay fill• Eroded channel material was pulled up from the bottom of the channel onto theinside batter and crest of the channel bank. The material placed on the crest wassurplus.• In some locations the crest of the banks was later rotary-hoed as cracks up to40cm in depth formed in the EBM material as soon as it dried out.Construction and Refurbishment of Earthen Channel Banks August 2002 - Edition 1.0 20-20