Characteristics and Controlling Factors of Gully Erosion (Case Study: Limited between Ahar-Meshkinshahr)

A gully is one of the most complicated linear erosion features due to multistage gully evolution under the control of the large number of factors along times. Gully initation and evolution usually results from a combination of natural and anthropogenic causes. Natural gulling processes are accelerated by intensification of farming system. Most of the times the gulling processes are triggered by inappropriate cultivation and irrigation systems, overgrazing, road building, land use changes is expected to have a greater impact on gully erosion than climate changes. The objective of this paper studies on impacts factors and control of gully erosion. In study area, gully erosion is a threshold depend processes controlled by a wide range of factors. Considering that for a given slopes (S) a critical drainage area (A) is necessary to produce sufficient runoff to concentrate and initiate gully thresholds lines. In this study, the relationship is S=0.407A4.54857 and value of S=A0.4 is from 4.04 to 21. 32 as initiate gully thresholds.These relations are suggested as indexes for estimating the location of gully generation. Finally multiple regression was used to include topographical parameters. This analysis shows that length of slope and hight diversity are relatived with length gully. Patterns and rates of gully network development as well as network geometric configuration are highly controlled by soil/lithological properties. Field observations and sample analysis of soil show that the typical gully developes on old alluvium sediments.