چکیده:
Gully erosion is widespread process of land degradation in dryland regions and has attracted the interest of a large number of researches. Although much research has carried out on soil erosion in arid and semi arid regions of Iran, few studies have been conducted to understand the threshold conditions of gully incipient. This study was conducted on gullying mechanism and topographic threshold conditions of gullies in an arid region of Iran. Since the dynamics of gully development channel initiation and extension are controlled by a variety of processes and factors, the data
collection and analysis consist of field studies to the determine predominance process responsible for incipient gullying and Digital Model Elevation (DEM) analysis to examine slope-area relationship. Soil attributes (EC and SAR) and landuse practices were known as major factors to initiate piping and the potential of this process to initiate gully is very significant for bank gullies. It seems that topography and soil attributes are the major factors determining the effective process for incipient gullying in our study area. In the other hand all of gullies occurred in
the main drainage streams and consequently are the main processes for landscape evolution. Correlation analysis showed an inverse linear relationship in log-log plot of upslope area and local slope dataset related to permanent gully heads. However for dataset associated with landsliding the S-A relation was not significant. Results of S-A relation can be used to determine vulnerable areas to gullying.
خلاصه ماشینی:
"Since the dynamics of gully development channel initiation and extension are controlled by a variety of processes and factors, the data collection and analysis consist of field studies to the determine predominance process responsible for incipient gullying and Digital Model Elevation (DEM) analysis to examine slope-area relationship.
In the second stage the entire environment data of upland area of gullies were, including: land use, ground cover, and gully head slope collected and finally in each site a soil profile was dug and soil samples were taken from different horizons to determine soil attributes.
In contrast to hillslope gullies that are formes due to critical flow shear stress at the soil surface, they are formed because of runoff overfalling from littoral bank area and tunnel or piping erosion caused by hydraulic gradients occur in dispersive materials (Poesen et al.
They separated their data based on dominance process into overland flow, landsliding and seepage erosion but they found that in all dataset, landscape and process an inverse relationship between area and slope is consistent with the form of Acr ∝ S-2.
In other words they concluded that the AS2 is the best indicator for predicting channel head location on the landscape and the form of Acr ∝ S-2 relationship is not affected by other environment factors such as soil and climate conditions and dominance process for gullying (Montgomery and Dietrich 1994).
The further analysis of these data was based on the (S=αA-β) relationship and the results revealed the following conclusions: 1-Dominance process for incipient gullying is controlled by soil material characteristics and topography of the landscape."