Extended Abstract

1. Introduction

Soil erosion has adverse economic, social, and environmental consequences on productivity, income distribution, and the environment, which may play a prominent role in national and transnational economies and sustainable development. Among water, wind, and glacial erosions, the erosion caused by water every year causes extensive damage all over the world. Water erosion is divided into four groups according to its importance and formation method, which include flood erosion, channel erosion, furrow erosion, and ditch erosion. Gully erosion is a common phenomenon in the climate of different regions, especially arid and semi-arid regions, and it affects large areas with different morphological, soil-geological, and climatic conditions. Among the environmental parameters that can affect the amount of gully erosion potential are hydrological, climatic, topographical, ecological, geological, and human. Trench erosion is the most visible form of soil erosion, leading to decreased soil production capacity and restrictions on land use. It can be a danger to roads, fences, and various structures and also causes significant soil losses and precipitation production. In order to control this phenomenon, it is important to know the effective factors and land zoning in relation to it.

2. Materials and Methods

In this research, statistical models are used to zone the occurrence of gully erosion in the north of Ahvaz. First, the location of the gullies was identified through field surveys and aerial photos using Google Earth software, and 34 gully erosion points were identified. Moreover, recorded and then physiographic maps (height, slope, distance from the river, watercourse density) were prepared using DEM with a resolution of 12 meters in ArcGIS 10.8 software. The Natural Resources Department of Khuzestan Province prepared the land use map, and the Khuzestan Water and Electricity Organization prepared the geological formations map. All the maps were then converted into grid layers and classified. The frequency ratio, statistical index, and Shannon entropy methods were used to calculate the gully erosion of the studied area.

3. Results and Discussion

In the land-use frequency ratio model, the barren land index (4.10) has the most significant role in ditch erosion in North Ahvaz. By changing the land use, farmers destroy the natural vegetation and plow the soil surface because the permeability of the soil is disrupted, the runoff volume increases, and the soil loses its strength. The excess runoff from agricultural land will cause the formation and expansion of gully erosion in the region, and the lowest parameter involved in gully erosion in the mentioned model is geological formations (0.07). In the statistical index method, in the order of land-use, barren lands index (12.93), geological formations (Quaternary valley deposits and terraces) (6.85) play the most important role in ditch erosion in the north of Ahvaz. In general, the depth and width of trench erosion are different in geological formations; the trenches in the north of Ahvaz are mainly on the level of fine-grained alluvial deposits of the Quaternary era, which are the result of the destruction and erosion of desert sediment formations (salt, chalk) and new alluvium (gravel, sand, clay, silt) are formed. This causes the erosion of ditches in this area. Due to its erodibility, the depth and width of trench erosion are greater than other formations in the study area, which is consistent with the findings of Oparaku and Lwar (2018). The parameters of height, slope, and distance from the river have the least effect on ditch erosion, respectively

4. Conclusions

A large part of the ditch erosion in the studied area is influenced by the distance from the river (7.96), not having a comprehensive view of the studied area, sectional changes in waterways, and inappropriate design in The outlets of the Karun Basin have caused the concentration of Herzabs and the beginning of ditch erosion in the north of Ahvaz. Also, the influence of Quaternary valley deposits and terraces (6.85) is one of the essential factors in creating ditches. The erodibility of this formation, the failure to observe the correct principles of cultivation and crop rotation in agricultural lands, and the change of land use cause disruption of the texture and structure of the soil. Another critical parameter in creating ditch erosion north of Ahvaz is the distance from the road (4.35). The road construction operation causes the concentration of upstream runoff in the waterways under the roads and the creation of ditches downstream of the road. The erosion of the ditch in the north of Ahvaz has led to the sliding of the slopes of the Karun River bed and is emptying the roads and coastal facilities. Due to the volume of road construction (road and bridge) and construction operations, the research area has intensified in recent years. Also, the evaluation results of the models using the qualitative summation method (Qs) showed that the statistical index model has the highest summation of quality (0.36). After that, the frequency ratio (0.24) and Shannon's entropy (0.22) models have the lowest index in terms of quality summation. The influence of climatic, geological, soil, and human interference factors on each other has caused severe gully erosion in the region. Taking into account the total of the above contents of the effective factors in the creation and spread of this type of erosion, we can conclude that although many factors are effective in the creation and intensification of ditch erosion, the variety and change in the number and extent of the influence of different factors from one point to another and the different contribution of their participation in the formation and expansion of ditches in accordance with the geo-environmental conditions requires more research to investigate and analyze the factors influencing the growth and expansion.

5.  Acknowledgment & Funding

The manuscript did not receive a grant from any organization

6. Conflicts of Interest

 The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. The authors declare no conflict of interest.