construction and refurbishment of earthen irrigation channel banks

13/08/02 19:20As with the damage to the inside batter, the outside batter may be eroded by stockwalking up and down the bank. In time, the phreatic surface may be breachedcausing leaks through the bank.Light stocking rates may be acceptable in some irrigation areas in order to reducevegetation growth which may become a fire hazard and habitat for noxious weedsand vermin.12.21.1.2 Damage due to adjacent land use practiceAdjacent farm operations may also increase maintenance costs and adverselyeffect the life of an earthen channel bank as follows:- using the bank as a farm access track for stock and vehicles- using bank as a headland around crops- locating farm irrigation channels immediately adjacent to the authority’schannel bank, so only one farm bank is required.- ‘borrowing’ of earth from the back of bank for farm use- storage of farming equipment or use as a rubbish dump- encroachment of channel tenure for croppingThe phreatic surface of the bank may be breached if earth from the outside batteris removed or if a farm channel is located nearby. This will cause the bank tobegin leaking which may lead to a piping failure of the channel bank.12.21.1.3 Unauthorised public accessUnauthorised access which may impact on channel bank includes:- Potholes and ruts on the crest and outside batters caused by vehicles- Dumping of rubbish which may impede access for operations and maintenance12.21.1.4 Waterway contaminationThe potential adverse environmental and water quality impacts caused by stockand other unauthorised access are:- contamination through the deposition of animal faeces directly into thewaterway- increased turbidity and nutrients (Nitrogen and Phosphorus) in the channelwater- increased possibility of toxic blue-green algae- spread of bacterial and viral diseases; eg Johnes Disease- spread of parasite eggs and cysts; eg Liver fluke- dead stock in channel causing general health risks- increased weed growth- chemical pollutants, such as spills from farm chemicals.- increased health risks to other farms and downstream water users12.21.2 Advantages and Disadvantages of Protective FencingConstruction and Refurbishment of Earthen Channel Banks August 2002 - Edition 1.0 12-54