بررسي كارايي مدل هاي EPM و MPSIAC در تعيين وضعيت فرسايش حوزه آبخيز شهرياري

Performance evaluation of EPM and MPSIAC Models for determination of Erosion Status of Shahriari Watershed

اطلاعات محدودي از دقت نقشه­­ ي فرسايش آبي به‌عنوان يكي از عوامل مهم تهديدكننده منابع خاك وجود دارد. به اين منظور، ارزيابي صحت و نحوه پراكنش طبقات فرسايش حاصل از مدل­هاي EPM و MPSIAC در مقايسه با مدل BLM به­عنوان مقادير واقعيت زميني در حوزه آبخيز شهرياري در اين پژوهش انجام شد. ابتدا آمار و اطلاعات موردنياز مدل­هاي MPSIAC، EPM و BLM براي دست‌يابي به وضعيت فرسايش حوضه­ جمع ­آوري و به كمك نرم‌افزار ARC/GIS9.3 نقشه­ هاي طبقات فرسايش تهيه و با نقشه واقعيت زميني تلاقي داده شدند. همچنين يك نقشه نقطه­ اي حاوي 1400 نقطه تصادفي براي نمونه ­برداري از نقشه­ هاي حاصل از مدل­ها تهيه و بر اساس اين نقشه، ميزان هر يك از شاخص ­هاي آماري RMSE،RRMSE ،MAE ، MBE، NSE، CD، CRM و MSE محاسبه شد. براي بررسي دقت و صحت مكاني نقشه­ هاي طبقات فرسايش حاصل از مدل­ها ماتريس خطا و ضريب توافق كاپا، صحت كلي، صحت توليدكننده و صحت كاربر تهيه شد. نتايج فرسايش حاصل از مدل­ها نشان داد كه ميانگين شدت فرسايش در مدل MPSIAC، 589 و در مدل EPM، 287 مترمكعب بر كيلومترمربع در سال برآورد شد كه وضعيت فرسايش حوضه با كمك مدل MPSIAC، زياد و مدل EPM، شرايط متوسطي را برآورد شده است. بررسي شاخص­هاي آماري فوق­الذكر نشان مي­دهد كه ميزان تطابق طبقات فرسايش مدل MPSIAC با خروجي BLM (به‌عنوان نقشه واقعيت زميني) بيشتر از مدل EPM است. همچنين نتايج ارزيابي صحت مدل­هاي MPSIAC و EPM نيز نشان داد كه مقدار ضريب كاپا در مدل MPSIAC بيشتر از مدل EPM است.

Soil erosion is one of the most important environmental issues in developing countries, including Iran that there is inaccurate information about its amount and distribution. For this purpose, the accuracy and distribution of erosion classes obtained from EPM and MPSIAC models as compared to BLM as ground truth values were evaluated in Shahriari watershed. First, the required data and information for MPSIAC, EPM and BLM models for basin erosion status was stored in a database. Then, using ARC/GIS9.3 software, erosion class maps were prepared based on each model formula and they have been intersected with the ground-truth map. Also a point map containing 1400 random points was also prepared for sampling the maps obtained from the models. Then, based on random sampling points map, each of the statistical indices of RMSE, RRMSE, MAE, MBE, NSE, CD, CRM and MSE were calculated. Also, to verify the spatial accuracy of the erosion class maps derived from the error matrix models and the Kappa coefficient of agreement, overall accuracy, producer accuracy and user accuracy. The results of the erosion of the models showed that the mean erosion intensity in MPSIAC model was 589 and in EPM model 287 m3/ km2.year that the basin erosion status is estimated to be moderate for the basin with the help of MPSIAC model and EPM model. The analysis of the above statistical indices shows that the RSME, MAE, MBE and MSE statistics in MPSIAC model have lower values. As a result, the MPSIAC model has less error than the EPM model. Overall, the results of the statistical indices showed that the MPSIAC model's erosion classes were more in line with the BLM output (as a ground truth map) than the EPM model. Also the kappa coefficient in MPSIAC is higher than in EPM model. Overall, the results show that the MPSIAC model erosion class maps overlap with the BLM model and in fact with the actual conditions of the area.