Importance ofselecting the appropriate digital elevation modelinmanagement of soil and waterconservation (Case study: Taham dam, Zanjn province)

Application of digital elevation model plays an important role in studies of management and protection of soil and water resources. In this research, ASTER-GDEMand SRTM-DEM and digitized contour lines of two topographic maps at 1:50000 scale are used as input data. The change of relief was modeled by nearest neighbor(NN) and inverse distance weighting (IDW) interpolation methods for downstream of Taham dam at north west of Zanajn province.Four digital elevation models were investigated by root mean square error, mean bias error, mean absolute error and correlation coefficient indexes. 100 auxiliary heights points along with reference control points using DGPS technique and surface network basis points were determined based on several field surveys.The results show that natural neighbor model and ASTER-GDEM data are more compatible(MBE index was 1.41 and 0.238 respectively) and inverse distance weighting model and SRTM-DEM are less compatible with control and reference points (MBE index was 10.045 and 6.296 respectively). Analysis of some primary components of topography affecting the soil erosion such as slope, aspect slope, length and class of stream represents the second generation of ASTER-GDEM is more accurate than others. It is suggested that ASTER digital elevation model to be used in areas with moderate topography and semi-detailedsoil protection and erosion control surveys. Application of ASTER-GDEM increases accuracy of the survey and reduce time and cost of performance of the management program about soil and water conservation.