construction and refurbishment of earthen irrigation channel banks

Vegetation to be encouraged on channel banks should have the following attributes:• binds the topsoil and withstands erosion throughout the year• prostrate or low growing species with widespread root system• preferably sterile, so that seed is not passed onto neighbouring land• spreads by rhizomes and/or stolons• covers the bank so that noxious weeds and other unwanted growth is reduced to aminimum• not invasive species which will be detrimental to the waterway• will regenerate naturally and provide a long-term, self-sustaining cover• must be easily controlled.• drought and disease resistant• requires little maintenance after establishment• able to establish quickly and give a good ground coverNo single grass will have all the desirable qualities and it may be necessary to use amixture of various grasses to provide continuous cover.If the area can be grazed, then a selection of locally used pasture species would beappropriate. However, stock access is not recommended practice. A non-seedingvegetation cover that spreads by runners, such as Kikuyu, has the potential tocompete with other plant species and reduce the noxious weed and fire hazardproblems on the channel reserve. Species which bind the soil with stolons orrhizomes (runners) are generally preferred to protect the bank from erosion.Vegetation species to be encouraged vary regionally. Table 17-2 lists holding grassspecies suitable for use in northern Victoria and southern New South Wales.Creeping salt bush (Atriplex semibaccata) has been used successfully to controlerosion on the faces of cuttings and embankments in arid zones, because of itsprostrate habit, rapid growth rate and ability to thrive on soils with low fertility andmoisture levels.African Star Grass (non-seeding variety) has been planted on the inside batters ofirrigation dams in northern New South Wales. It provides some protection fromwave erosion and can extend over the crest if conditions allow.In Queensland there has been little specific study into suitable vegetation for anyone irrigation area. The current procedure employed by QDNR Engineering is thatwhen a project is proposed a detailed assessment of the site conditions is carried outand forwarded to the Department of Primary Industries for a recommendation.Some of the issues to be considered when selecting vegetation for protective coverare as described in section 17.6.4.Construction and Refurbishment of Earthen Channel Banks August 2002 – Edition 1.0 17-8