A B S T R A C T
Erosion forms can also indicate the intensity of erosion and sediment yield in a watershed. The Qarnaweh Olya watershed in northeastern Golestan Province is covered with loess sediments, which are highly susceptible to water erosion. Human activities have also contributed to water erosion in various forms, including sheet, rill, and gully erosion. This study aims to determine the sediment yield of each erosion form and understand their impact on increasing the sediment load in the area. To achieve this, the erosion class maps in the area were initially prepared using the MPSIAC and RUSLE models. Statistical indices such as RMSE, MAE, MSE, and NSEC were employed to evaluate their accuracy, along with the baseline model BLM, which was based on factors obtained through field observations. Since the map produced by the MPSIAC model had greater overlap with the actual conditions of the area, this model was utilized to determine the degree of sediment yield in the erosion forms. Then, the relationship between erosion forms and sediment yield was analyzed using variance analysis. The results, with a confidence level of 0.99, indicate that there is a significant difference in sediment yield among the different erosion forms in the region, with each form contributing uniquely to sediment production. Therefore, models that consider the differences between these forms can provide more accurate sediment yield predictions. Additionally, the highest sediment yield was associated with gully erosion, reaching a value of 57, followed by rill and sheet erosion. These results contribute to improving the accuracy and efficiency of sediment estimation and can be useful for erosion control and targeted conservation measures in the watershed.
Extended Abstract
Introduction
Various forms of water erosion are severely intensifying the loss of nonrenewable resources, pollution, and land degradation, threatening the sustainable development of agriculture. Although most methods for assessing soil erosion rates are directly related to the forms of erosion and their intensity in an area, few studies comprehensively examine the spatial distribution of all forms of water erosion in a single study. The Qarnaweh Olya Watershed is an area extensively covered with loess sediments, and erosion in this watershed occurs in various forms as sheet, rill, and gully erosion, each playing a different role in sediment production. The Qarnaweh River, in particular, has become a large, unstable gully in some areas, with significant depth and severe erosion. Examining the forms of erosion and their sediment yield allows for the identification of critical areas and improves the accuracy and efficiency of sediment estimation. Furthermore, the type of proposed work and the implementation of conservation projects vary depending on whether the area is affected by sheet, rill, or gully erosion. Therefore, a precise and scientific understanding of the impact of these forms of erosion on sediment yield in watersheds is essential. In this context, the present study was conducted to identify the forms of water erosion in the area and analyze the specific contribution of each to sediment production in the Qarnaweh Olya Watershed.
 
Methodology
The Qarnaweh Olya Watershed is located in the east of Golestan province, in the geographical location of 55° 49¢ to 56° 02¢ and east longitude is 37° 38¢ to 37° 45¢ north latitude. A comprehensive research method was employed to achieve the study’s objectives, including field data collection, remote sensing, and Geographic Information System (GIS) analysis. After identifying various forms of water erosion in the area, including surface, gully, and rill erosion, erosion class maps were prepared using the MPSIAC and RUSLE models. To evaluate their accuracy, statistical indices such as RMSE, MAE, MSE, and NSEC were utilized, along with the base model BLM, for which all factors were obtained through field observations. Since the map produced by the MPSIAC model had a greater overlay with the BLM model and the actual conditions of the area, this model was used to determine the sediment yield of the erosion forms. Based on the relevant relationships and depending on the intensity of their effects, scores were assigned to the layers of factors influencing erosion and sediment production, including geology, soil, climate, runoff, slope, land cover, and land use. Statistical analyses, including variance analysis, were performed to evaluate the significant differences in sediment production among different erosion forms. The analysis was performed at a 99% confidence level, ensuring the reliability and validity of the results.
 
Results and discussion
The analysis of statistical indicators in this study showed that the MPSIAC model has higher efficiency than the RUSLE model. Therefore, according to the relationships related to this model, scores were assigned to the layers of influencing factors, and the degree of sedimentation from erosion forms was obtained. The results showed that sediment yield from various forms of water erosion in the area changes with different variables and is influenced by factors such as rock type, elevation, climate, runoff, slope, soil, vegetation cover, and land use. These factors affect the development of different erosion forms, from sheet erosion to gully erosion. However, among these factors, geology, runoff, and land use not only influence the formation of various erosion forms but also their intensity. Specifically, the average sediment yield from advanced gully erosion is higher in the layers associated with geological factors, runoff, and land use than in other erosion forms. In another stage of the study, the changes in their sediment yield rates were also identified based on the overlap of the sediment yield map with the erosion forms map in the area. The results indicated that from sheet erosion to gully erosion, both the intensity of erosion and the amount of sediment production increase. The highest average sediment yield in the area was found in gully erosion, with a value of 56.99. Statistical analysis confirmed that the differences in sediment production between the various erosion forms are statistically significant. The analysis of variance (ANOVA) results indicated that each erosion form has a unique impact on sediment production, influenced by the interaction of environmental and human factors. The significant contribution of gully erosion to sediment production highlights the urgent need for targeted conservation measures in the studied watershed.
 
Conclusion
This study investigated the existing forms of water erosion in the Qarnaweh Olya Watershed, including natural, sheet, rill, and gully erosion. To determine the sediment yield degree of each type of erosion, the total scores of various factors related to the MPSIAC model were used because evaluating the accuracy of the models using the baseline model BLM and comparing the results of the statistical indices RMSE, MAE, MSE, and NSEC showed that the spatial distribution map of erosion classes from this model has higher accuracy than the RUSLE model. The results showed that the highest average sediment yield among the area's water erosion forms is related to gully erosion. Therefore, gully erosion has the most significant role and contribution to the increase in sediment yield compared to other forms of erosion in the area, as it leads to greater soil loss due to the greater depth and higher volume of variable water flow. Thus, effective watershed management in the area requires special attention to controlling and reducing gully erosion. An analysis of variance was used to assess the significance of the differences between the forms of erosion in the area concerning their sediment yield. The results, with a confidence level of 0.99, indicated that the sediment yield of the erosion forms in the area differs significantly from each other, and each erosion form has a specific contribution to sediment production. Therefore, water erosion forms can be more effectively used to estimate erosion and sediment yield. Indeed, models considering the differences between these erosion forms can achieve more accurate sediment yield predictions.
 
Funding
There is no funding support.
 
Authors’ Contribution
Authors contributed equally to the conceptualization and writing of the article. All of the authors approved thecontent of the manuscript and agreed on all aspects of the work declaration of competing interest none.
 
Conflict of Interest
Authors declared no conflict of interest.
 
Acknowledgments
We are grateful to all the scientific consultants of this paper.