Bank erosion prediction and mitigation measures along the lower Mekong river
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Abstract
The Lower Mekong River area is a zone with plenty of natural resources and it has the highest agricultural production in Vietnam. The river passes though six provinces in the Southern patt of Vietnam, with more than 16 million in habitants in total. However, serious riverbank erosion problems occur and there is no master plan or mitigation strategy to prevent this problem. Given these conditions, the first objective of this Master of Science study was to study bank erosion prediction by means of both empirical methods and numerical methods. The second objective is to study possible mitigation measures, especially the use of revetments, bend cut-off, and permeable groynes. Based on a number of satellite images (1987, 1996, 2000), old map (1937, 1966) and the observed topography data at some locations, empirical methods to predict riverbank erosion were studied, tested and modified. It appeared not possible to derive an empirical method which in generally applicable in the Lower Mekong River. A numerical model was developed amongst others to make of riverbank erosion predictions. This model was properly calibrated and verified against data from measurements. In an early state of numerical model development, riverbank erosion prediction along the Lower Mekong River was tested with the model. In this testing, the sensitive of parameters in the bank erosion module of MIKE21 C were checked for the Tan Chau -Hong Ngu reach. To prevent (predict and mitigate) riverbank erosion is a very challenging task in river engineering. The mitigation measures were studied by a comprehensive approach, which reviewed the existing mitigation measures in the lower Mekong river, and subsequently fare an overview of possibility preventive measures in this area. Finally, one case study, notably the critical reach near Tan Chau, was taken considering three kinds of measures: a revetment, a bend cut and permeable groynes. The numerical model was used to predict (i) the scour hole in front of revetment, and (ii) the effect of the bend cut. Also the application of the permeable groynes was studied, but these appear to be less suitable for the specific conditions at Tan Chau.