Assessment of potential erosion and monitoring of gully dynamics in the Upper Ouergha (Central Rif, Morocco)

The land in the Aoulai watershed in the Rif mountain area of northern Morocco has been deteriorating continually due to several different forms of erosion. The Aoulai watershed is essentially characterized by the domination of weak resistance of the rocky formations and its sensitiveness to other major internal factors that result in a conspicuous impetus for both mass movements and water erosion.Water erosion is seen as the most damaging phenomenon for nature in northern Morocco because it acts as an obstacle to the natural balances and seems to have greater effect on the slopes, through the influence of both human and natural factors. To assess and examine the erosion phenomenon, we have chosen to conduct a qualitative assessment of water erosion in the Aoulai watershed using the PAP-RAC (Priority Actions Programme/Regional Activity Centre) Guidelines. This is the methodology that is most widely applied and implemented both for determining and identifying the areas at risk of erosion and for supporting projects to reduce the degradation that has become a major threat to hydraulic structures including dams, irrigation pipes and other infrastructure elements, which are damaged by the erosion phenomenon in the Central Rif mountains of northern Morocco.

The human impact, combined with the geomorphological, lithological, and climatic specificities of northern Morocco, makes the soils highly vulnerable to the risk of water erosion. The primary purpose of this research is to map and assess the soil water erosion vulnerability in the Boussekour watershed, located in the Rif Mountain chain in northern Morocco, by applying the erosion potential method (EPM) developed by Gavrilović. It is an approach that involves integrating, within a Geographic Information System (GIS) environment, six parameters involved in the erosive phenomenon: temperature, rainfall, slope, soil erodibility, current erosion, and soil protection. The input data necessary for applying this model were derived from satellite images, digital elevation models (DEMs), granulometric and physico-chemical analyses of soil samples, and local rainfall data. Results show that the high erosion class (from 20 to 40 Mg∙ha−1∙yr−1) is prevalent and acts on 45% of the watershed, while the low (from 5 to 10 Mg∙ha−1∙yr−1) and very low (from 0 to 5 Mg∙ha−1∙yr−1) erosion classes account for just 6.98% and 1.44% of the area, respectively. This result demonstrates that the Boussekour watershed is profoundly threatened by soil water erosion, and an effort ought to be made to promote operative soil conservation efforts.

The present article aims to evaluate soil losses due to water erosion and to contribute to the knowledge about the impact of vegetation cover on the Isser watershed that is located in northwestern Algeria. For this purpose, two predictive models were used, namely the Priority Actions Program by the Regional Activity Center (PAP/RAC) model and the revised universal soil loss equation (RUSLE) model, using the geographic information system (GIS). To illustrate the level of protection in that watershed, it was decided to use two approaches for the estimation of factor C; the first one is the classical method and the second consists of calculating the normalized difference vegetation index (NDVI) during two periods (dry and wet). The map of erosive states, which was obtained from using by the PAP/RAC model, shows the areas that are potentially most vulnerable to erosion and which cover more than 60% of the total area of the basin. The results for vegetation cover (factor C) by the conventional method during the dry period present an average land loss equal to 14 (t ha−1 year−1), whereas this rate decreases to 7.9 (t ha−1 year−1) during the wet period. According to the NDVI approach, the factor C results for the dry season are 25.53 (t ha−1 year−1) with an annual land loss of up to 3 million tons. This study provided the qualitative and quantitative estimates needed for the development of the environmental management; it also helps to control the different impacts on that watershed.

The purpose of this study is to quantify soil surface erosion using the Universal Soil Loss Equation in GIS environment and to assess its impact on soil humus reserve. The quantifying of soil surface erosion was performed by integrating in GIS the thematic raster representations of the erosion control parameters which exhibit spatial variability within the limi ts of the study region (Dobrovăţ Basin, The Central Moldavian Plateau, eastern Romania). Soil erodibility was computed according to ICPA (1987) standards, on the basis of soil type, texture and erosion degree, using a soil map of the basin at scale 1: 5000. Slope length was derived from a 20m resolution digital elevation model using SAGA-GIS software, while slope factor was determined according to the Romanian methodology by raising the slope values at the power of 1.5. Finally, the vegetation factor was computed on the basis of the normalized difference vegetation index derived from a 2001 Landsat image, using the equation proposed by Van der Knijff et al. (1999). Subsequently, we derived the potential soil erosion, controlled exclusively by soil-relief factors and the effective soil erosion, by integrating the effect of vegetation. The potential soil erosion show a mean value of 15.6 t/ha yr and a standard deviation of 16.6 t/ha yr. The integration of the vegetation effect decreases the mean value to 5.4 t/ha yr and the standard deviation to 6.7 t/ha yr. Most of the basin’s surface (48.7%) falls into the reduced erosion risk class (2-8 t/ha yr), while the high and very high erosion risk classes group 7.3% of the basin. The assessment of the erosion impact on soil carbon stock was performed by coupling the USLE model with a Hénin -Dupuis mono-compartmental humus evolution model. The simulation was performed for the first 20cm of the soil profile, using a database of 224 soil profiles. The results of the simulation show that 76% of the soil profiles display a regressive evolution of the humus reserve under the impact of the soil erosion. The mean humus loss for these profiles is 36.3 t/ha for 100 years of simulation.

A pragmatic approach for soil erosion risk assessment within policy hierarchies

Erosion following fire has the potential to affect water quality, alter soil profiles and detrimentally affect human infrastructure. There is a clear need for environmental assessments to have regard for erosion concerns from prescribed burning. This study focussed on 10 prescribed burns conducted in the Southern Mount Lofty Ranges. Generalised additive modelling was used to determine the main significant environmental variables influencing the presence of sediment movement at 505 field-assessed sites. Sediment movement after the 10 prescribed burns was minor. Fire severity was a highly significant environmental determinant for the presence of sediment movement after prescribed burning. To predict erosion concerns, a suite of environmental variables is more reliable than focusing solely on slope steepness, as occurred before this study. These results indicate that erosion assessments need to consider a range of environmental variables to assess potential erosion and that land managers and scientists need to incorporate spatial sampling designs into erosion assessments.

Multi-criteria decision analysis for monitoring and evaluating soil erosion risk in forest fire-affected areas.

Australia’s metalliferous abandoned mine sites (MAMSs), pose tangible threats to the environment and human health. To address these concerns, our study utilised state-of-the-art handheld XRF technology to conduct a real-time assessment of the Mole River arsenic mine site. The data revealed notably elevated levels of arsenic and manganese, with the southeast corner of the site identified as a contaminant hotspot. We used a tiered risk assessment approach to compare the detected contaminant concentrations to the Australian health investigation levels (tier 1). This led us to a broader examination of erosion vulnerabilities and the potential migration of contaminants (tier 2). Further, a hydrological assessment (tier 3) identified significant erosion in southern regions, indicating the potential for contaminants to be transported off-site through surface water runoff to Sam’s Creek and Mole River. The proximity of a reservoir to these runoff pathways brought forth additional challenges, especially during heavy rainfall events. Subsequent laboratory analysis of water samples reinforced our findings, as they confirmed heightened arsenic concentrations in Mole River downstream, accentuating the potential risks to ecosystems and human health. By integrating the XRF contour map and erosion assessment with the RUSLE model, valuable insights are gained into critical hotspots with high contamination and erosion potential. By directing rehabilitation efforts towards critical hotspots, resources can be allocated more efficiently and cost-effectively.

تعتبر التعرية الـمائية من أكثر الاخطار البيئية تهديدا لاستقرار الأوساط الطبيعية عبر العالم، وخاصة بالمجالات الجافة وشبه الجافة، ومنها جبال الريف بالـمغرب، حيث تعرف اقتلاع كميات مهمة من التربة خاصة المواد الدقيقة منها، مما يؤدي إلى تدهور خصوبة التربة بالمجالات الزراعية، وبالتالي تراجع كميات إنتاجيتها. تتطلب معالجة هذه الظاهرة اتباع مناهج ومقاربات عدة؛ منها التقييم الكمي للتعرية المائية اعتمادا على المعادلة العالمية لفقدان التربة، والتي تعمل على تكميم التعرية الغشائية انطلاقا من دراسة العوامل الطبيعية والبشرية المسؤولة عن هذه الدينامية، لتحديد كمية الأتربة المفقودة حسب مختلف العوامل، بواسطة نظم المعلومات الجغرافية وتقنيات الاستشعار عن بعد. أظهرت النتائج المتوصل إليها بحوض واد برون، أن كميات الأتربة المفقودة بلغت في المتوسط 29,4 طن/هـ/سنة، مع وجود تباين مجالي من نطاق لآخر داخل الحوض، وذلك تبعا لاختلاف العوامل المسؤولة عن فقدان التربة بالمجال. نهدف من خلال هذه الدراسة إلى تصنيف الحوض حسب درجات خطر تدهور التربة، لتحديد المجالات التي تستدعي تدخلا عاجلا من طرف الجهات المعنية، من أجل تسهيل اتخاذ القرارات المناسبة لمحاربة ظاهرة التعرية المائية واستصلاح المجالات المتضررة منها.

The negative impact of maritime traffic in terms of shore erosion in sheltered coastal fairways can be mitigated by sustainable fairway management. Mitigation measures include regulating the ship traffic in terms of speed, routes, or size of ships, but can also involve erosion protection along a fairway. For effective shoreline management of a fairway, it is essential to predict ship waves, to identify sites with potential erosion problems, and to investigate the effectiveness of different measures before implementing them. Several attempts have been made to develop site-specific criteria for managing ship waves. However, few available generic models consider primary waves generated by large ships in confined fairways. Therefore, a tool for supporting decisions in fairway management was developed. The decision support tool is based on simplified formulas for ship- and wind-wave prediction, combined in a framework that enables automatic, rapid assessments on large spatial and temporal scales. Moreover, the tool requires only readily available input data, such as data on AIS, bathymetry, shoreline geometry, wind, fairway centreline, and grain size. The output from the model includes ship and wind wave heights and potential erosion sites. The decision support tool was applied to the Furusund Fairway, Sweden, by simulating one year of ship traffic to validate its capability of identifying potential erosion sites. The simulation demonstrated that the tool was capable of identifying known erosion sites in the fairway. Additionally, scenarios with different speed regulation strategies for the Furusund Fairway were investigated using the decision support tool. Overall, it is concluded that the developed tool enables rapid assessment of ship waves, wind waves, and potential erosion over large areas in fairways.

Mapping Potential Soil Erosion Risk Areas in Abia State, Nigeria Using Geographic Information System (GIS) and Remote Sensing (RS) The study used Geographic Information System (GIS) to integrate data from Remote Sensing (RS) to map out areas that are prone to erosion in Abia State, Nigeria. This was done using the index model and weighted overlay of ArcGIS software. The result showed that about 0.18% (2.325 ha) of the study area, covering the northern part (Abriba and Nkporo areas) and Ikwuano areas is under very high potential erosion risk, while 0.92% (11.475 ha) is under high erosion risk. The high erosion risk areas in the north are all located on the top of the escarpment running from Isuochi, through Isuikwuato, Ohafia and down to Arochukwu.Also 20.98% (262.54 ha) of the study area, covering the following Local Government Areas - Umuahia South, IsialaNgwa North, IsialaNgwa South, Osisioma, Obingwa, Aba North and Aba South is under moderately high erosion risk, while 34.51% (431.82 ha) is under moderate erosion risk and 43.49% (543 ha) covering the Ukwa/ Ngwa area, whose topography is gentle to no slope falls under low potential erosion risk. The study showed that using RS and GIS technologies for erosion risk/hazard mapping, based on the methodology used, resulted in effective and accurate assessment of soil erosion in considerable short time and at a low cost for large study areas or watersheds. It is recommended that Government Agencies and private should explore the advantages offered by RS and GIS in delineating erosion prone areas for planning and design of structures.

<p>A quantitative assessment of the potential soil erosion on arable land in the European part of Russia (EPR) was carried out. The total area of arable land of the EPR is about 650,000 km<sup>2</sup>. The majority of the population of Russia lives here - about 95 million people. The level of generalization of work is regional and corresponds to a scale of 1: 500,000.</p><p>As a research method, mathematical modeling based on modified for Russia’s natural conditions USLE equation for calculating potential soil loss from erosion. Another leading method for assessing soil erosion and presenting results is GIS. A raster model of data presentation was used in the calculations, including a model of slope angles, slope lengths, soil erodibility, erosive rainfall potential, water reserves in snow, intra-annual redistribution of rainfall, and land use types.</p><p>New data have been obtained on the value of soil erosion losses during melt and storm runoff periods and total annual losses. An electronic map of soil erosion losses on arable lands of the European part of Russia has been compiled, which allows determining spatial features of soil erosion rates.</p><p>The average soil erosion losses, taking into account the soil-protective coefficients of agricultural crops for the study area, are 4.04 t / ha per year. In annual soil losses due to erosion, storm 3.78 prevails, soil loss from melt water is almost an order of magnitude less - t / ha 0.26. About half of the territory is located in conditions under which the soil loss does not exceed 0.5 t / ha per year.</p><p>The rate of potential soil erosion on arable land in the European part of Russia naturally decreases in the direction from the taiga-forest to the steppe landscape zone. The band of maximum potential soil erosion of the west-east sub-latitudinal strike is clearly distinguished, confined to the subzone of mixed and broad-leaved forests with very high plowing. A comparative analysis of our data and data obtained in the mid-1980s showed a reduction in soil loss from water erosion in all landscape zones. In addition, a comparative analysis of the data obtained by us and the data for the European Union was carried out, which showed that the soil losses on the EPR are slightly higher.</p>

Soil erosion is an important global phenomenon that can cause many impacts, like morphometry and hydrology alteration, land degradation and landslides. Moreover, soil loss has a significant effect on agricultural production by removing the most valuable and productive top soil's profile, leading to a reduction in yields, which requires a high production budget. The detrimental impact of soil erosion has reached alarming levels due to the exacerbation of global warming and drought, particularly in the arid climates prevalent in Tunisia and Algeria and other regions of North Africa. The influence of these environmental factors has been especially evident in the catchment of Mellegue, where profound vegetation loss and drastic changes in land use and cover, including the expansion of urban areas and altered agricultural practices, have played a significant role in accelerating water-induced soil loss between 2002 and 2018. The ramifications of these developments on the fragile ecosystems of the region cannot be overlooked. Accordingly, this study aimed to compare soil losses between 2002 and 2018 in the catchment of Mellegue, which is a large cross-border basin commonly shared by Tunisian-Algerian countries. The assessment and mapping of soil erosion risk were carried out by employing the Revised Universal Soil Loss Equation (RUSLE). This widely recognised equation provided valuable insights into the potential for erosion. Additionally, changes in land use and land cover during the same period were thoroughly analysed to identify any factors that may have contributed to the observed risk. By integrating these various elements, a comprehensive understanding of soil erosion dynamics was achieved, facilitating informed decision-making for effective land management and conservation efforts. It requires diverse factors that are integrated into the erosion process, such as topography, soil erodibility, rainfall erosivity, anti-erosion cultivation practice and vegetation cover. The computation of the various equation factors was applied in a GIS environment, using ArcGIS desktop 10.4. The results show that the catchment has undergone significant soil water erosion where it exhibits the appearance of approximately 14,000 new areas vulnerable to erosion by water in 2018 compared to 2002. Average erosion risk has also increased from 1.58 t/ha/year in 2002 to 1.78 in 2018, leading to an increase in total estimated soil loss of 54,000 t/ha in 2018 compared to around 25,500 t/ha in 2002. Maps of erosion risk show that highly eroded areas are more frequent downstream of the basin. These maps can be helpful for decision-makers to make better sustainable management plans and for land use preservation.

Comparison of EPM and PSIAC models in GIS for erosion and sediment yield assessment in a semi-arid environment: Afzar Catchment, Fars Province, Iran

A GIS-based assessment of the potential soil erosion and flood hazard zones in Ekiti State, Southwestern Nigeria using integrated RUSLE and HAND models