Contour banks have been constructed on South Australian farms for many decades to reduce the effects of water erosion on sloping, arable land.
The banks are surveyed according to the lay of the land and constructed to prevent water run-off from scouring into the topsoil, thereby creating channels that can have a severe effect on good cropping and grazing country.
In severe rain events, the banks slow run-off so that it does not have sufficient velocity to pick up soil particles – the beginning of the erosion process.
Properly designed contour banks protect productive farming country from the ill effects of flooding and help prevent soil and crop nutrients and chemicals attached to soil particles from entering natural watercourses.
Heathdon, a 1,100-hectare cropping and grazing property near Appila, has been in the Bottrall family for almost 130 years. Over almost a decade from 1949, Stewart Bottrall established contour banks on the property with the survey expertise of the then Department of Agriculture and with earthmoving equipment hired from the local Council.
The first of the banks were created in 1949 as an urgent response to severe rain events and significant loss of topsoil. Further banks were established between the period from 1955 to 1958, and they served their purpose well for almost 40 years.
However, Stewart’s son, Don, who now runs the property, recognised that with more advanced surveying designs, new contour banks could be even more effective in harnessing a natural resource while preventing erosion.
Apart from his family experience and records on the farm, Don has been a member of the West Broughton Soil Board.
His expertise and drive has been instrumental in creating a showpiece of improved contour banking techniques made possible in partnership with the Northern and Yorke Natural Resources Management Board.
With funding support from the Board, Don arranged a qualified surveyor to create a new contour plan for the farm. Having cleared the old contour banks, about 14km of new banks were established with the farm grader. They are further apart with a different alignment to the original banks, and a greater fall to prevent water from forming ponds behind the banks.
Board funding assisted in the development of new contour banks over an area of about 165 hectares which have the added benefit of being more suited to modern farm machinery.
Don believes the banks offer erosion protection beyond other control strategies, such as retaining stubble and reducing tillage to prevent topsoil run-off.
“It has been a very successful outcome and the support of the Northern and Yorke Natural Resources Management Board made the whole process easier,” he said.