Gholm Reaza Rahi; A Kaviyan; K Soleimani; H Pourghasemi
Abstract
Creating a gully is a reaction to the geomorphologic conditions, this type of erosion extends over a wide range of environments, and the threshold of topography is related to the slope and drainage level and Controls the position and expansion of gullies in different uses. The slop-area equation as a ...
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Creating a gully is a reaction to the geomorphologic conditions, this type of erosion extends over a wide range of environments, and the threshold of topography is related to the slope and drainage level and Controls the position and expansion of gullies in different uses. The slop-area equation as a relationship between the slope and the upstream area of the watershed in any area will in part help predict gully erosion. The above relationship has been influenced by several factors including environmental conditions (climate, lithology, soil type), the type of land use, and the type of effective mechanisms for the creation and expansion of the gully (surface flow, sub-surface flow, dissolation, and piping), and the type of method used for extraction of slope - area is located. And this is the simplest formula used by two parameters to predict gully erosion. The results show that the value of the relationship between -0.233 and -0.205 was obtained. The equation for agricultural use was equal to Y = 5.7426X-0.205and for the pasture use equal to Y = 10.653X-0.233. In this equation, the power can be close but the coefficient of the equation is different. Gully erosion of the whole hinterland (farmland, agriculture) is expanding. The threshold of topography indicates a negative relationship between land area and slop in different kind of agricultural and rangeland. By reducing the slope, more area is needed for the development and expansion of the gully, and most of the gully is due to surface runoff.
mahvash gholami; karim soleymani; esmaeil nekoee
Abstract
Landslide is one of the major natural hazards caused financial losses, in lives and destruction of natural resources each year. The aim of this study was comparisons of three models, namely WofE, FR and DSH to the determination of the landslide prone areas in Sari-Kiasar watershed. In the first, 105 ...
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Landslide is one of the major natural hazards caused financial losses, in lives and destruction of natural resources each year. The aim of this study was comparisons of three models, namely WofE, FR and DSH to the determination of the landslide prone areas in Sari-Kiasar watershed. In the first, 105 landslides occurred in the study area were collected based on aerial photographs in the 1:25,000 scale and field studies divided into two group haphazardly to generate training 75% and testing 25% dataset. Then, 17 landslide conditioning factors including geological, geomorphological, hydrological and anthropogenic were prepared to spatial relationship with landslide occurrence in the study area. The most important factors in the occurrence of landslides in the study area were rainfall followed by slope and vegetation. The validation results as a percentage of the cumulative area under the curve (AUC) showed that the success rate of WofE, FR and DSH models are 92.05, 92.05 and 91.31 percent respectively and the prediction rate are 92.72, 92.73 and 85.44 percent respectively. The results show that in terms of the accuracy of the model used to base on success rate, three models are placed in excellent group (0.9 to 1), also in terms of the accuracy of the model used to base on prediction rate, WofE, FR models are placed in excellent group (0.9 to 1) and DSH is placed in good group (0.8 to 0.9). The results showed that the WofE and FR model have a higher prediction accuracy than of DSH model.
