Monitoring of Soil Loss from Erosion Using Geoinformatics and Geotechnical Engineering Methods

Abstract

In this study, the position of all major rill and gully erosion sites were located using hand held GPS (Global Positioning System) receiver during reconnaissance surveys. Based on severity rating and geopolitical considerations, six of the erosion gully sites were selected for monitoring. Control points were established around each of the gully sites using three Leica 500 dual frequency GPS receivers by method of DGPS (differential GPS) surveys. Detailed topographical survey of the gully sites was carried out using total stations. With the aid of SPOT satellite imageries in combination with total station data and GIS (geographic information system) location maps, contoured maps along with DEM (digital elevation model) were generated using ARCGIS 9.2 software. The morphological parameters of the gullies including depth, width, length and area of the gullies were determined. Volumetric estimate of the amount of soil loss from gully erosion was also carried out. Soil samples were recovered from the gully sites to determine their erodibility and other parameters to be used for soil loss modeling. The result of the studies was used as an indicator for determining the gully initiation point. Slope-area relationship and threshold of gully initiation was established. The minimum volume of soil loss occurred in gully No. 2 (Queen Ede). The minimum AS 2 value was 345 while the maximum was 3,267.