The Role of Hydrologic Processes in Formation of Gullies Based on the Area-Slope Relationship in Arid Regions of Markazi Province

Gully erosion is a serious threat to the society and environment of the study, primarily caused by surface runoff and dramatically accelerated due to rugged topography, soil properties and human induced factors. Therefore, the objective of this study was to investigate hydrologic processes affecting gully formation by topographic indexes in arid regions of the Markazi Province. Then threshold of the slope -area in the gully regions of Robattork and Pik-e Zarandie were determined. A logarithmic equation was developed using the morphometric characteristics of the gullies, the slope-area relationship at Robat-Tork was highly correlated and the b coefficient was negative. The investigations revealed surface flow with dissolution action was involved in this area. In the Pik-e Zarandie region, this correlation wasn't strong, but it was significant at the level 95%. In this region, the effect of surface flow and dissolution phenomenon on the gully formation was also evident. In addition to the importance of the climate, gully categorizing based on land use can be achieved with better models. Therefore, it is necessary to determine the indices of topographic thresholds that best reflect the conditions of the local physical environment and land cover/use.