construction and refurbishment of earthen irrigation channel banks

13/08/02 19:20However, fencing of channels tends to be a contentious issue with landholders and shouldnot be treated lightly.12.21.1 Reasons for Protective Fencing of ChannelsIt is important that the banks of a channel are protected from physical damagecaused by stock, adjacent farm operations or other unauthorised access as describedin section 12.21.1.1 to 12.21.1.4.The channel waterway should also be protected against deteriorated water quality,stock diseases and contaminants which may be passed to downstream users.12.21.1.1 Stock DamageIn Goulburn-Murray Water, livestock damage has been found to reduce channelbank life significantly. Most of the damage caused by stock on channel banks isrelated to stock using the channel as a drinking trough.stock damagePhoto 12-2Erosion of channel bank caused by stock accessStock can cause quite extensive damage to channel banks. In the heavy stockingareas of northern Victoria, new unfenced channel banks constructed from lightfriable soils can be effectively destroyed by stock within a year.Stock damage to channel banks results in material being pushed into thewaterway, steepening of channel batters, erosion, damage to structures andreduced bank life which impacts on the flow capacity of the channel as well asincreased maintenance costs.Both sheep and cattle can cause damage to earth banks. Sheep trample and grazechannel banks bare, exposing the bank material to rain and wind erosion. Cattledamage can be very serious, trampling and pugging up the banks and waterway,particularly where cattle use the channel bank to access water.Cattle cause steepening of the inside batters of channels as they walk down to thewater’s edge, which may deteriorate further due to wind and wave action. Theinstallation of stock watering troughs away from the channel bank will reduce theamount of damage that occurs.Channel banks may be used as a stock laneway, wet weather stock holding area,storage of hay and for stock feeding. Where the channel bank is used as alaneway for stock, the access track requires increased maintenance. Stock usingan access track in wet weather can render it impassable for operation andmaintenance vehicles. The crest of the channel bank can be damaged quite badlywhen used for access during wet conditions as ruts and potholes can be formed.In dispersive soils this can lead to the development of sink holes and possiblepiping failure.Construction and Refurbishment of Earthen Channel Banks August 2002 - Edition 1.0 12-53