Land use changes cause changes in the hydrological cycle components and increase or decrease the amount of runoff and erosion in the watershed. Some land use changes become one of the most important problems in some watersheds all over the globe as the case in Ziarat watershed in Golestan province, Iran. Therefore, investigated the impacts of optimal scenario for development of residential areas on soil loss caused by surface runoff and raindrops using the TOPSIS method and WetSpa spatial hydrological distributed model in this study. ArcGIS-based TOPSIS multi-criteria decision making model was used to forman optimal scenario of residential development. WetSpa model inputs consist of digital maps including digital elevation model, land cover and soil texture (with 30 m cell size) and continuous time series of precipitation, evaporation and air temperature over hourly step for 6 years (2007–2013). The accuracy of flow simulations for the calibration period, depending on the Nash-Sutcliffe model efficiency was 67.02% and the suspended sediment concentration and sediment yield were 63.08% and 72.22%, respectively. According to the evaluation criteria considered in this study and using TOPSIS method, 37 hectares of the total watershed area is proper for residential development, but now the residential area of this watershed is more than 141.3 hectares. The amount of soil loss due to raindrops in the whole reference period was 381.54 kg/s and the amount of soil loss due to surface runoff was 227.715 kg/s. After applying the optimal residential development scenario in the WetSpa calibrated model, the amount of soil loss due to surface runoff and raindrops was compared in the two scenarios of current residential status and optimal residential development scenario. The results showed that the amount of soil loss due to surface runoff decreased significantly, but the soil loss caused by raindrops increased. Finally, as the amount of soil loss caused by surface runoff is significantly reduced compared to the soil loss caused by raindrops, the amount of total soil loss decreased.

土地用途的变化会引起水文循环成分的变化，并增加或减少流域的径流和侵蚀量。某些土地利用变化已成为全球一些流域中最重要的问题之一，例如伊朗Golestan省的Ziarat流域。因此，本研究使用TOPSIS方法和WetSpa空间水文分布式模型研究了居民区发展的最佳方案对地表径流和雨滴造成的土壤流失的影响。基于ArcGIS的TOPSIS多标准决策模型用于确定住宅开发的最佳方案。WetSpa模型输入包含数字地图，包括数字高程模型，土地覆盖和土壤质地（单元大小为30 m）以及连续的降雨时间序列，每小时的蒸发和气温持续6年（2007-2013年）。取决于Nash-Sutcliffe模型的效率，校准期间的流量模拟精度为67.02％，悬浮泥沙浓度和泥沙产率分别为63.08％和72.22％。根据本研究中考虑的评估标准并使用TOPSIS方法，总流域面积的37公顷适合住宅开发，但现在该流域的住宅面积超过141.3公顷。在整个参考期间，雨滴造成的土壤流失量为381.54 kg / s，地表径流引起的土壤流失量为227.715 kg / s。在WetSpa校准模型中应用最佳住宅开发方案后，比较了当前居住状况和最佳居住发展情景这两种情景下由于地表径流和雨滴造成的土壤流失量。结果表明，地表径流造成的土壤流失量明显减少，而雨滴引起的土壤流失却增加。最后，由于与降雨引起的土壤流失相比，由地表径流引起的土壤流失量大大减少，因此总土壤流失量减少了。