Soil erosion modeling using GIS and RUSLE on the Eurajoki watershed , Finland

Abstract

This thesis study applied Geographical Information System (GIS) and the Revised Universal Soil Loss Equation (RUSLE) to predict the annual average soil loss rate from the Eurajoki watershed (South-West Finland). To achieve the goals of the thesis, the RUSLE factors were calculated using the local data that was collected from National Land Survey of Finland and Finnish Metrological Institute. The soil survey data were used to develop the soil erodibility factor (K), and a digital elevation model of the catchment was used to generate the topographic factor (LS). The values of cover-management (C) factor and support practice (P) factor were collected from literature due to lack of satellite image and soil index map. Usually C and P factors determine from land cover and land use classes respectively. The rainfall–runoff erosivity (R) was derived from monthly rainfall data and Fournier index.

The results indicate that the average annual soil loss (A) within the catchment is about 5 Mg/ha/yr (5 metric ton per hectare per year). This is highly depend on R value which ranges between 299 and 307 MJ/ha.mm/h with the highest values being in the lower part of the catchment and the lowest values in the higher part of the catchment. Slopes in the catchment varied with steep slopes having higher values of slope length and mean LS factor is 1.34.

It is also important to note that the steepest slopes show high risk of soil erosion, it is therefore recommended that further study be undertaken to establish the suitable soil and water conservation measures that should be implemented in these areas as well as the whole catchment.