construction and refurbishment of earthen irrigation channel banks

13/08/02 19:20The disadvantages of fencing channels includes:- capital cost- loss of stock access to water- loss of grazing area- grass growth on the channel may become a fire hazard and habitat for vermin.However these disadvantages can be overcome as described in Table 12-14.Disadvantages of FencingThe additional direct costassociated with constructionand maintenance of thefence.Vegetation can become afire hazard and allow thegrowth of noxious weedswithin the fenced channeltenure. High vegetationcover may provide a habitatfor vermin which may alsoburrow into the bank.Loss of stock grazing areaand access to waterRestricted plant access formaintenanceManagement of Disadvantages of FencingWhere longitudinal fencing is not constructed, it is often necessaryto install cross-fences where property boundaries cross the channeltenure. Cross-fences require the installation of a flow hurdleacross the channel waterway, which are expensive to install andmaintain.To prevent vegetation growth from becoming excessive,encouraging vermin and becoming a fire risk, light stocking orother measures as described in Section 17, Protective Cover mayreduce the problem. In Goulburn-Murray Water, grazing by lightanimals such as juvenile cows and sheep is allowed for shortperiods after permission is granted by the Area Manager, understrict guidelines.Landowners can provide water for their stock by stock troughs ordams on their properties.Provide sufficient space between bank and fenceTable 12-14Management of Disadvantages of Fencing12.21.3 Location of Protective FenceWhere a fence is located too close to a channel bank there can be insufficient roomfor effective maintenance and access by plant and equipment. Therefore thedesigner should delineate sufficient room for maintenance activities and plantaccess between the fence and bank.The fence should be placed on the boundary of the channel tenure, with at least 1metre from the outside toe of the channel bank. If space is available, a distance of 2to 3 metres from the bank toe to the fence line is recommended for smallerdistribution channels and up to 5 to 6 metres for larger channels.12.21.4 Use of Stock Grids versus GatesStock grids are sometimes used instead of gates at access points such as crossroads.Their main advantage is that operators do not need to open gates.The disadvantages of stock grids are:- stock grids are not absolutely stock proof and stock could be injured if forcedover the grid- gates would be required in any case to allow stock access for controlled grazingConstruction and Refurbishment of Earthen Channel Banks August 2002 - Edition 1.0 12-57