Gully Erosion Classification in Kermanshah Province using Relative Similarity Analysis with Morphometric and Soil Auxiliary Variables

Gully erosion is one of the main sources of soil loss in watersheds and also one of the main causes of sediment storage in dam reservoirs and river alluvium. In addition, human activities can exacerbate this erosion, which has very worrying consequences. Therefore, the present study was conducted to determine the environmental thresholds of gully erosion and also the morphoclimatic classification of these areas in Kermanshah province.

To do this, first by collecting information from relevant authorities and also using aerial photographs 1: 20,000 and 1: 50,000, the main gully of the province that were visible on the pictures and then this information using field operations and specifying them on corrected on topographic map. Climatic zones of gully in the province were identified using existing maps based on the modified Domarten method. Then, in each climate, one to three gully were identified as targets, and in each of them, a representative gully was identified and two replications were identified, and the field identification of these gully was completed by field operations and field visits. These characteristics included location, land type, dimensions at the head of the gully and at intervals of 25, 50 and 75% of the top, length, profile and general plan of the gully. In addition, soil sampling was performed in the above sections and some physical and chemical properties of soil were measured in the laboratory. The classical statistical method of cluster analysis was also used to classify gully.

The results of this study showed that there are differences in the important morphometric characteristics and topographic threshold of the studied gully in different gully in the province and in different climates, which are mainly due to the climate, type of formation, topography and vegetation of this area. Classification of gully based on the classification method showed that with a similarity level of 97.5%, three general classes can be identified for gully.

gully areas in arid desert climates (warm regions) of the province in one class, gully zones located in the middle altitudes and cold semi-arid climate in the second class and gully zones in cold semi-arid climates to the Mediterranean colds are in the third class similar to gully. The active gully of the province are mainly located in the hill and plain lands. The results of this study show a picture of effective and influential factors in creating gully, based on which it is possible to apply how to control them in future planning and management of officials.