Investigation of mechanisms of erosion and sediment studies in Afjeh and Lavarak sub-basins using experimental models and compare them with geostatic methods

Afjeh and Lavarak sub-basins each with area of 4651,95 and 10557,2 hectare are located at south border of central Alborz at north-eastern of Tehran. Various formations basically contains Shaly, Sandstone, Conglomerate and tuff lithology, covered this region more than igneous rocks. In Afjeh sub-basin, Barout formation with the age of Cambrian and in Lavarak sub-basin, Mila formation with the age of middle and late Cambrian, are the oldest available stones and the newer stone units belong to Quaternary period in each of them. The purpose of this research is to compare MPSIAC and EPM models in calculation of sediments supply and soil erosion, using GIS techniques. To achieve the goals, effects of lithology, soil texture and geological conditions on sediment production were considered by sedimentological and petrographic studies. Finally with use geostatisticaloperations, two models were compared. The results show that the most values of erosion are in Shaly, Marly, weathered tuff and alluvial deposits Parts of sub watersheds correlated with sensitive formations such as Karaj and Quaternary sediments. Based on map of MPSIAC model more than 75% of the total sub watersheds area was classified at class IV of erosion category with high sedimentation. Sub-basin’s erosion were calculated as 769.3 and 583.21 m2/km3 per year in Afjeh and Lavarak sub-basins by MPSIAC and 701. and 543.2 m2/km3 per year by EPM models, respectively. The results of statistical compare of erosion of MPSIAC and EPM models show that, there is no significant different between erosion estimate by MPSIAC model and real erosion measure, but the erosion estimate by EPM model have a significant different. So MPSIAC model may have better performance.