A PROPOSED APPROACH OF SEDIMENT SOURCES AND EROSION PROCESSES IDENTIFICATION AT LARGE CATCHMENTS

Abstract

In the subject of identifying sediment sources and erosion processes at catchment level researchers have proposed various methods. Most of the techniques have been applied in isolation. A few workers have combined some methods but still they could not ascertain their findings. As a result they recommended more sophisticated methods in order to compare the results. Little however has been done to correlate suspended sediment concentrations using spatial and temporal hydrological variables like rainfall and surface runoff at reasonable time step such as daily time series. In this study selected methods by previous workers are used and compared. The hydrological variables mapping technique has complemented the results of various renowned sediment sources identification techniques. The introduced method gives not only probable sources and processes but also it additionally identifies location based sediment sources using rainfall stations as pointers. The combined results from both methods indicate that either clay soil land plots or agricultural areas are potential sediment source areas. The result is comparable to previous researchers' findings in the Pangani River basin that mapped the erosion zones using simple empirical and complex physics-based mathematical models. Although, the methods adopted in this study lacked high-resolution data, the authors believe that the methods and modifications applied give a quick, reliable and more insight to future sediment yield modelling efforts at a catchment level. For instance, a distributed watershed sediment yield model would be appropriate based on high spatial and temporal variation of the hydrological variables as reported in this study. Also, the results suggest that Sediment yield model that simulates sheet erosion might be an ideal tool since the major source areas of the transported sediment are topsoils or sheet erosion.