| چکیده انگلیسی مقاله |
Introduction and Goal
One of the types of water erosion that causes erosion and sediment in watersheds and causes a lot of damage to agricultural lands, range lands and infrastructure is gully erosion. By identifying the causes of gully erosion, land managers can prevent the expansion of gullies by considering and observing effective management factors. This research was conducted with the aim of examining gully erosion in the provinces of the country, identifying the factors influencing the expansion of gully erosion, determining the area affected by gully erosion, and estimating the damages resulting from it. In addition, the extent of the expansion of gullies in the classes of different factors and the damage caused by gullies in Iran were investigated
Materials and Methods
The materials used in this research are research projects that directly and indirectly focus on the expansion of gully erosion. Initially, several of the most important factors influencing gully erosion in the watersheds of the country were examined. Then, all classified factors and their relationships with areas affected by gully erosion were analyzed. In this research, the climates of gully-affected areas were classified using the extensive Dummartin method, and the relationship between different climates and the frequency of gullies was examined and calculated. Comparison of old and new land uses in gully areas, soil texture and range of soil particle changes, EC changes, organic matter changes, SAR changes in gully areas, slope, road construction, and plowing in the slope direction as some of the most important. The effective factors were investigated in the expansion of gully erosion. Finally, the area of gully erosion occurred along with the type of damage and the estimated amount of damage has been estimated based on daily prices for the provinces.
Results and Discussion
The results of the analysis of the relationship between different climates and the frequency of gullies indicated that 32% of gullies are in semi-arid climates, 17% in dry climates, 14% in dry and hot desert climates, 14% in dry and temperate desert climates, and 9% in Mediterranean climates, 5% occurred in semi-humid climates, 4% in humid and dry cold desert climates respectively, and 1% in very humid climates. The comparison of old and new land uses in gully areas showed that 55 %of the gullies were created as a result of changing the land use of rangeland to dry farming agriculture. Silt Loam, Loam, and Sandy Loam are the dominant soil textures in gullies with 26, 23, and 20%, respectively. 14% of the studied areas have very severe restrictions in terms of salinity. The amount of organic matter in the studied areas varies from 0.02 to 2.9%. The organic matter of 94% of the gully areas was less than 2%, and the organic matter of about 6% of the areas varied from 2 to 2.9%. The results of the sodium absorption ratio study showed that the sodium absorption ratio of 24% of the gully areas was greater than 15. The slope of 70% of the gully areas was less than 12%, 16% of the gully areas were in the slope class of 12 to 25%, and 14% of the gully areas were in the slope class of more than 25%. In 38% of the gully areas, road construction and in 27% of them, plowing in the direction of the slope were identified as factors affecting gully erosion.
Conclusion and Suggestions
Based on the results of this research, the highest frequencies of gullies were observed in semi-arid climates rain fed agriculture and the soils with silty loam texture. Additionally, gullies have expanded in areas with very severe salinity limitations, very low organic matter, and high sodium absorption ratios. In some areas, road construction and plowing in the direction of the slope are also known as effective factors in gully erosion.
Based on the results of this research, the damage caused by the expansion of Iranian gully was calculated to be about 700 billion Tomans. Also, due to the onset of a long-term drought period, it is suggested that conservation plans (biological) and in some cases combined (biological and structural) be used to reduce the expansion of Iranian gullies. Also, in areas where improper agricultural practices have led to the expansion of gullies, farmers should be educated, particularly in the area of proper plowing techniques. Additionally, in the studied areas, land use change was identified as the most significant human factor affecting the occurrence of gully erosion. Therefore, it is recommended to avoid land use changes. |