THE QUANTITATIVE ESTIMATION OF THE SOIL EROSION USING USLE TYPE ROMSEM MODEL. CASE-STUDY- THE CODRULUI RIDGE AND PIEDMONT (ROMANIA)

This paper proposes a quantitative estimate of the current annual rate of soil surface erosion in the Codrului Ridge and Piedmont (due to the pluvial denudation and sheet erosion) and a spatial representation of the results by implementing GIS techniques. The database used in the application of the ROMSEM model (Romanian Soil Erosion Model) was consisting of Digital Elevation Model (DEM) with a resolution of 10 m, for computing the topographic factor (LS), soil map (with information about the type, texture, structure and degree of soil erosion), land use map, based on Corine Land Cover 2000 and corrected according to ortophotos dating from 2005, with a 0.5 m resolution, and the rainfall erosivity index map in Romania. The estimation of the surface erosion in the Codrului and Piedmont Ridge was achieved in two stages: first was assessed the potential erosion (the peak value of the erosion in an area devoid of vegetation) based on the climatic, topographic and soil factors. The effective surface erosion map was obtained in the second stage of the mathematical modeling erosion, by integrating the effect of natural or crop vegetation. The thematic map obtained was aligned to the present Romanian legislation (order no. 223 of May 28, 2002); the superficial erosion intensity map includes five classes: insignificant erosion <3 t ha(-1) yr(-1), low erosion: 3-10 t ha(-1) y(-1), moderate erosion: 10-20 t ha(-1) yr(-1); high erosion: 20-40 t ha(-1) yr(-1), very high erosion: >40 t ha(-1) yr(-1). The results obtained indicate an average annual rate of erosion of 0.575 t ha(-1) yr(-1) and a quantity of material discharged by surface erosion of 55,561 tons per year. 97.46 % of the study area has tolerable values (<3 t ha(-1) yr(-1)), revealing the low degree of human intervention, a good vegetation cover and the domination of the slopes with low inclination, less susceptible to erosion.