Channel planform dynamics of an alluvial tropical river



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Texas A&M University


The meandering stream has been well studied in temperate environments but the same level of research has not been achieved for meandering streams in tropical areas. The overall objective of this research was to gain an increased understanding of meandering planform dynamics in humid tropical rivers. The objective was pursued by examining the rate of change of channel pattern and results indicate that migration rate and the range of radius of curvature to width ratio where maximum migration occurs is similar to those reported for humid temperate rivers. In summary, as regards to these aspects, the results suggest that the representative humid tropical river is no more dynamic than its temperate counterparts. A second objective was to document the response and recovery of a humid tropical river system to an extreme flood event. As a result, the trend of shorter recovery times following a major perturbation was demonstrated, and suggests that in the long term, a large flood such as a 100-year event apparently plays a relatively minor role as a formative event in shaping the overall humid tropical landscape. A third objective was to develop an empirical model for predicting bend migration rates in humid tropical rivers, resulting in empirical relationships that indicate that meander migration has a high degree of correlation with the number of bankfull discharge events under all scenarios, and that model correlation can be enhanced when the silt-clay composition of the banks, and the radius of curvature to width ratio are included as independent variables. The resulting equations were tested to predict maximum meander migration distance, and predictions produced very satisfactory results. In addition to increasing basic understanding of meander processes in tropical areas and for developing fluvial geomorphological theory, the results of this research have potentially important benefits to society. Because property and structures are often threatened by channel movement, there is a need for improved predictive capability of deformation of stream channels, and the results can therefore be useful to engineers and other professionals in delineating channel hazard zones.