Ndomba, Preksedis M.; Mtalo, Felix W.; Killingtveit, A.
Description:
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.