Tools for Remotely Assessing Riparian Buffers Protecting Streams from Sediment Pollution in Nzoia Basin, Kenya

摘要

A software package was assembled and evaluated for assessing soil erosion potential due to agricultural developments in Nzoia River basin (Kenya). Google Earth Pro was used to define site characteristics. Extensive analysis of components of UniversalSoil Loss Equation (USLE) and the US environmental protection agency (USEPA) sediment delivery ratio method was made to determine erosion potential and sediment yield respectively. A paired t-test comparison between GPS and Google Earth derived elevations showed difference between the elevations but the error margin was within the GPS unit's error margin of 5 meters. The ground truth results obtained from measured data often small watersheds yielded mean absolute error of 0.76 tons ha~(-1) yr~(-1) withR~2 of 0.95. With regard to the field of application of the tools described in this study, the accuracy levels are acceptable. The Moore and Sergoit bridge sites located near Eldoret, Kenya were analyzed. The predicted average soil loss and sediment yield at Moore's bridge site was 192 and 1.8 tons ha~(-1) yr~(-1) respectively while at Sergoit site was 5.3 and 0.05 tons ha~(-1) yr~(-1) respectively. It was deduced that Google Earth Pro is useful for initial surveys in extracting site topographic and land use patterns. The Preliminary results suggested that agricultural pollution is not a threat in this particular region but would become as more riparian zones are cleared. Also, the rainfall energy, crops grown, and soils of the region are similar to those of southeast US. Therefore, the US experience would be applicable.