Tools for Remotely Assessing the Impact of Riparian Buffers Protecting Streams from Sediment Pollution

Abstract

A software package was assembled and evaluated for assessing the potential of soil erosion due to agricultural development within the Nzoia River basin (Kenya). Google Earth Pro was used to define site characteristics. An extensive analysis of the components of the Universal Soil Loss Equation (USLE) and the US Forest Service sediment delivery ratio method was made to determine erosion potential and sediment yield respectively. The paired t-test comparison between GPS elevation and Google earth derived elevation 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 for Watkinsville (US) and Bukora (Uganda) watersheds compared to the predicted values yielded 6 % average deviation and 10.5 % average deviation respectively with R2 of 0.995. The Moore and Sergoit bridge sites located near Eldoret, Kenya were analyzed. The predicted average soil loss at Moore’s bridge site was 192 tons ha-1 yr-1 with a stream sediment yield of 1.8 tons ha-1 yr-1 while at Sergoit site is 5.3 tons ha-1 yr-1with a stream sediment yield of 0.05 tons ha-1 yr-1. It was deduced that Google Earth Pro is useful for the 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 of the region is close to that in the US, common crops of the US are in production, and the soils of the region are of the Ultisol and Oxisol classification (southeast US). Therefore, the US experience would be applicable.