Abstract—Today, incorrect use of lands and land use changes, excessive grazing, no suitable using of agricultural farms, plowing on steep slopes, road construct, building construct, mine excavation etc have been caused increasing of soil erosion and sediment yield. For erosion and sediment estimation one can use statistical and empirical methods. This needs to identify land unit map and the map of effective factors. However, these empirical methods are usually time consuming and do not give accurate estimation of erosion. In this study, we applied GIS techniques to estimate erosion and sediment of Menderjan watershed at upstream Zayandehrud river in center of Iran. Erosion faces at each land unit were defined on the basis of land use, geology and land unit map using GIS. The UTM coordinates of each erosion type that showed more erosion amounts such as rills and gullies were inserted in GIS using GPS data. The frequency of erosion indicators at each land unit, land use and their sediment yield of these indices were calculated. Also using tendency analysis of sediment yield changes in watershed outlet (Menderjan hydrometric gauge station), was calculated related parameters and estimation errors. The results of this study according to implemented watershed management projects can be used for more rapid and more accurate estimation of erosion than traditional methods. These results can also be used for regional erosion assessment and can be used for remote sensing image processing. Keywords—Erosion and sedimentation, Gully, Rill, GIS, GPS, Menderjan Watershed I. INTRODUCTION HE problem of land degradation and soil loss is a major problem in the all countries. Erosion by water is a primary agent of soil degradation at the global scale, affecting 1094 million hectares, or roughly 56% of the land experiencing human induced degradation [21,12]. Soil erosion is the most important limitation for the sustainable development, optimal land and water management and development. The understanding of the most important factors on soil erosion and sediment yield are the main keys for decision making and planning. Masoud Nasri: Ph.D student of Islamic Azad university, science and research Branch, Faculty of Agriculture and Natural Resources, Department of watershed management, Tehran, Iran, Email: ps_sepahan@yahoo.com Sadat Feiznia: Professor, University of Tehran, Karaj, 3158777878, Iran, Email: sfeiz@ut.ac.ir Mohammad Jafari: Professor, University of Tehran, Karaj, 3158777878, Iran , Email: jafary@ut.ac.ir Hasan Ahmadi: - Full Professor, University of Tehran, Karaj, 3158777878, Iran In recent years, most of the regions in the world are exposed to degradation and erosion caused by increasing population and over use of land resources. Soil erosion has been recognized as the major cause of land degradation world wide. In the past decades, priority of research has been given to address agricultural issues at the plot scale and thus to rill and inter-rill erosion [24]. This is explained by an increasing concern for off-site impacts of soil erosion that can be tackled only at the catchment scale. It is now well recognized that increased exploitation of land resources in the upper parts of catchments results in increased sediment yield and elevated nutrient loads in runoff that reduce water quality and availability to downstream users. Furthermore, control of sedimentation in reservoirs requires that all the potentially significant sediment sources and sinks are known. Recent studies [27,14,5,11] indicate that gully erosion is often the main source of sediments. Gully erosion has been long neglected because it is difficult to study and to predict. In recent years, most of the regions in the world are exposed to degradation and erosion caused by increasing population and over use of land resources. Logan et al., (1982) expressed the need for quantifying soil erosion processes and factors as an essential task for investigation. Land cover, soil conservation practices, and the presence of soil erosion control measures all influence actual soil loss. Land users can modify all of these. Measuring erosion is costly and time consuming whereas results may be conditioned by single events such as rain storms [13]; Lal (1994a) called it an art rather than a science. Calibration requires soil loss data from the full range of field situations for which the model will be applied. In practice, calibration is often based on data from few runoff plots with or without use of an artificial rainfall simulator [6], and/or on data from sites in other environments and/or measured according to nonstandard techniques [15,16]. All of these limit the predictive capacity of soil erosion models [4]. Monitoring schemes based on field measurement and the estimation of the volume of rills and gullies in a time span such as several years, are necessary in order to assess erosion at the landscape scale [22]. Using Field Indices of Rill and Gully in order to Erosion Estimating and Sediment Analysis (Case Study: Menderjan Watershed in Isfahan Province, Iran) Masoud Nasri, Sadat Feiznia, Mohammad Jafari, Hasan Ahmadi T World Academy of Science, Engineering and Technology International Journal of Geological and Environmental Engineering Vol:2, No:7, 2008 69 International Scholarly and Scientific Research & Innovation 2(7) 2008 scholar.waset.org/1307-6892/10620 International Science Index, Geological and Environmental Engineering Vol:2, No:7, 2008 waset.org/Publication/10620