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University of Mohaghegh Ardabili (2017)

Predicting the impacts of vegetation management scenarios on erosion and sediment yield using RUSLE in the Rozechai Watershed, Urmia

Haji, Khadijeh

Titre : Predicting the impacts of vegetation management scenarios on erosion and sediment yield using RUSLE in the Rozechai Watershed, Urmia.

Auteur : Haji, Khadijeh

Université de soutenance : University of Mohaghegh Ardabili

Grade : Master Thesis 2017

Résumé
Soil erosion is one of the environmental problems which can be considered as a threat for natural resources, agriculture and the environment. Thus, determining the temporal and spatial extent of soil erosion is an effective way to management of soil erosion and sediment control through watershed management. The soil erosion rate is different among various land uses have, thus, the vegetation cover have a great impact on soil conservation and erosion control. The objective of this study was to estimate and compare the rate of soil erosion in different land uses over 1985, 2000, and 2015 in Rozechai Watershed in North West Urmia using RUSLE model. Towards this attempt, the revised universal soil loss equation was used in a GIS framework and Landsat 5 and Landsat 7 satellite imagery and land use maps were prepared using TerrSet software and object-oriented classification. The input parameters of RUSLE model including R, K, LS, C and P maps were prepared and the erosion map in different management scenarios through overlaying the input layers. The twenty land use-based management scenarios have been developed considering the condition of the watershed considering improvement and degradation approaches. Results showed that the average amount of soil erosion rate is estimated to be 14.71, 16.52, and 17.22 (ton/ha/yr) in study years. According to the extent of rangelands with respect to other land uses, its decreasing trend shows a degradation process of rangelands conversion to rainfed agriculture. The values of Kappa index were 91%, 84% and 94% for the 1985, 2000, and 2015 years, respectively. The erosion amount was 17.22 (ton/ha/yr) in the base scenario (current condition). Through applying conservation practices in dry agriculture on steep lands, the scenario 6 (conservation and restoration of plowed rangelands) would reduce the erosion rate from 17.22 to 9.75 (ton/ha/yr). While the highest amount of erosion is estimated to be 30.42 (ton/ha/yr) due to severe degradation and overgrazing of the rangelands. Accordingly, the highest amount of erosion reduction is 43.37% in scenario 6 (conservation and restoration of plowed rangelands). Thus the effect of P-factor (support practice factor) was greater than C-factor (crop/vegetation and management factor) on reducing the amount of erosion. The results indicates the possibility scenario-based framework in assessment of the effects of management scenarios on erosion and prioritization of soil conservation in the study area.

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