The Mekong River in the Mekong Delta is an actively bifurcating system of river channels. Erosion of river banks is associated with rapid channel migration. Where bank erosion threatens infrastructure or urban or agricultural development, various agencies have employed bank treatments in an attempt to limit erosion. Most commonly these treatments involve replacing the natural interface between land and water with a concrete revetment barrier.
This paper reports on an alternative approach to erosion control funded by AusAID over 2 km of river bank in 2001. The purpose of the erosion control work was to reduce the risks posed by channel migration to a major AusAID funded bridge over the Mekong River at My Thuan near Vinh Long. Recent observation (March 2013) suggests that the bank which had been migrating at between 6 and 35 m/yr prior to treatment is now stable.
The treatment comprised a series of 12 separate lines of submerged concrete piles extending out from the river bank approximately 100 m. The dimensions and layout of these groynes including the spacing between groynes and the spacing of piles within the groynes were determined following physical modelling at the Vietnamese Institute of Water Resources Research in Hanoi. The modelling tested the velocity reduction through the pile fields against velocity criteria to stop scour of sediment on the bed of the river.
Echo sounders, divers and Acoustic Doppler Current Profilers were used to monitor the performance of the prototype during and post construction but no monitoring has been undertaken since 2004. Recent observation attests to the success of the approach and also suggests low aesthetic and environmental impact compared to areas of concrete bank revetment upstream and downstream.
A program of monitoring has now been developed to test the success of the approach and to demonstrate its benefits.