# Soil Erosion Estimates in Arid Region: A Case Study of the Koutine Catchment, Southeastern Tunisia
## 5 Conclusions  
Under the current climate variability, the study site is characterized by arid conditions and extreme inter-annual and spatial variability in total rainfall. This study conducted in the Koutine catchment showed that the arid regions of Tunisia, despite their low and variability annual rainfall, could be subject to significant rates of water erosion. The use of finer DEM resolution (12 m) as a basis of this work allows an appropriate and even an optimal level of precision for the quantification of erosion at a local scale (pixel level). We opted for the use of the modified Fournier index to determine \(R\) factor values. The superposition of the different model layers allowed us to compute the different parameters and obtain an annual rate stretching between 0 and 70 t/ha/yr with an average rate of 1 t/ha/yr. Obtained results were validated by the field measurements. The average annual soil loss in selected sites in the Koutine catchment during the monitoring period varies between 0.01 and 12.5 t/ha/yr. A maximum of 7.3 t/ha per event was registered in the upstream after a specific event. The importance of soil loss depends on the slope, and it was more than the permissible limit of 12 t/ha/yr in the upstream and 0.227 t/ha in the downstream area. It was also shown that cisterns could be used as effective soil erosion monitoring sites in dry regions. Obtained results can be used for planning purposes to develop mitigation strategies for soil erosion management. In addition, the results can be used to design water-harvesting techniques, especially in the upstream area, and eventually to decrease soil erosion.  
The developed RUSLE model is quite reliable and can be continuously updated based on future available data. Additionally, it can serve as a science-based decision supporting tool which can be extrapolated to the regional level for sustainable development of soil and water management plans.  
The following are available online at [[https://www.mdpi.com/article/10.3390/app11156763/s1](https://www.mdpi.com/article/10.3390/app11156763/s1)]([https://www.mdpi.com/article/10.3390/app11156763/s1](https://www.mdpi.com/article/10.3390/app11156763/s1)), Table S1: Particles size distribution and soil structure of samples from impluviums areas, Table S2: Particles size distribution and soil structure of samples taken from different sites in the Koutine catchment.  
Study design and organisation, M.B.Z. and M.O.; data collection and GIS analysis M.B.Z., S.J. and M.O.; RUSLE model setup and run, M.B.Z.; verification and validation of results S.J. and M.O.; writing and manuscript review, M.B.Z., S.J. and M.O. All authors have read and agreed to the published version of the manuscript.  
This research was conducted as part of the research program of the Eremelogy and Combating Desertification Laboratory (LR16 IRA01) at the Arid Regions Institute (IRA), Medenine, funded mainly by the Ministry of Higher Education and Scientific Research in Tunisia.  
Not applicable.  
Data Availability Statement: The measured and modelled soil erosion data in the study area are available upon request from the corresponding author. The original time series meteorological data are not publicly available due to restrictions of the National Insistite of Meteorology (INM) and Regional department of the Ministry of Agriculture (CRDA). Data related to land use and digital elevation model were generated from the open access portals [[https://earthexplorer.usgs.gov/](https://earthexplorer.usgs.gov/)]([https://earthexplorer.usgs.gov/](https://earthexplorer.usgs.gov/)) and [[https://www.usgs.gov/](https://www.usgs.gov/)]([https://www.usgs.gov/](https://www.usgs.gov/)) (accessed on 23 June 2021), respectively.  
We thank [PERSON], [PERSON] and [PERSON] for their technical and field assistance. We gratefully acknowledge all the colleagues who participated in managing the field trips and laboratory analysis. The comments of three anonymous reviewers improved the paper significantly.  
The authors declare no conflict of interest.  
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