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Water erosion poses a significant environmental threat in the Mediterranean region, with pronounced impacts observed throughout Morocco. It impairs soil quality and disrupts both sediment transport and water availability. Contributing factors range from natural (climate, topography, and geology) to anthropogenic (land use, vegetation cover, and management). This study introduces an improved Priority Actions Program/Regional Activity Centre (PAP/RAC) model, enriched with GIS and the Caesium-137 (137Cs) technique, to investigate erosion within Morocco's Raouz basin. Enhanced with additional variables including soil types, slope length, rainfall erosion potential, slope orientation, soil moisture, and land surface temperature, the model transcends the classical approach, promoting granularity and precision in predictions. In addition to the comprehensive model, the 137Cs method, which discerns long-term soil erosion and redistribution, provides a dual-faceted validation, bolstering the robustness of this project's erosion risk evaluation. This study's outcomes underscore the gravity of the erosion hazard with significant soil depletion rates ranging from 8.1 to 20 t ha−1 yr−1, demonstrating the model's alignment with empirical data, affirming its utility. The modified PAP/RAC model concurs with the 137Cs data, demonstrating its usefulness for water erosion assessment and management in similar areas. • The modified PAP/RAC model enhances erosion prediction. •Model validated with extensive 137Cs data. •GIS integration identifies erosion hotspots. •A comparative study with global erosion data. • The model adapts to diverse Mediterranean climates. [ABSTRACT FROM AUTHOR]

Hydro-morphological threats impact the natural physical characteristics of river ecosystems, such as flow regimes, sediment transport, and channel morphology. These negative effects can occur at multiple scales, ranging from local microhabitats to geographic regions. Understanding these interactions can be useful for an integrated conservation approach and is needed for effective freshwater management. The aim of the study was to elucidate the combined effects of hydro-morphological threats on macroinvertebrates at three spatial scales: macroscale, including whole catchments, mesoscale (hydro-morphological changes in individual river sections) and the microscale, describing the microhabitat conditions of European rivers. The diversity and trophic structure of 1120 local macroinvertebrate communities in 28 catchments of various hydro-morphological disturbance levels, ranging from 0 to 2400 m asl, were analyzed. The response of macroinvertebrates to the main disturbance gradient differed between mountain and lowland communities. Random forest analysis indicated that the most important predictor of the ecological, diversity, and trophic indices was described by flow rate reduction. Generalized additive mixed models showed that decreased flow combined with river incision explained most of the variation in macroinvertebrate indices. Our results emphasize that based on multi-spatial scale analysis, hydro-morphological threats are very important factors in invertebrates biodiversity loss. Thus, to implement effective river management, we should pay more attention to the combined effects of geomorphological threats. • Hydro-morphological disturbances lead to the loss of invertebrate biodiversity. • The effects of hydro-morphological pressure were studied at various spatial scales. • Incision and flow reduction described most of the river macroinvertebrates variation. • The most favourable microhabitats for macrofauna are shallow and redeposited sites. • Efficient river management should focus on the combined effects of multiscale threats. [ABSTRACT FROM AUTHOR]

The complexity of micro-tidal inlets arises from the combined action of littoral drift and tidal range on their stability. Consequently, understanding and evaluating their stability poses a significant challenge. This study aims to shed some insight on the assessment of inlet stability by employing Delft 3D model. The stability of the inlet between the ocean and estuary relies on the balance between the longshore transport rate and the spring tidal prism. Disrupting this equilibrium results in the closure of the inlets. The movement of sediments in the surf zone is primarily driven by longshore velocity, which acts as the driving force for littoral drift, which is estimated using Delft 3D wave model. The longshore transport rate is estimated by employing empirical relationships and numerical codes based on the obtained driving force. Subsequently, the stability of the inlet is assessed based on these estimations. The spring tidal prism refers to the discharge of water flowing into the ocean from inlets and estuaries. Flow velocity is determined using Delft 3D flow model. The input data for nearshore circulation resulting from waves and currents is primarily collected through field measurements and data collected from I ndian N ational C entre for O cean I nformation S ervices (INCOIS). For the current study, Muttukadu (12°47′13″N, 80°15′01″E) inlet, Kovalam along the East Coast of the Indian Peninsula is investigated by assessing its seasonal variations. This study contributes to the management of marine biological ecology, the expansion of small-scale artisanal fishing, the promotion of water sports-related tourism, the advancement of fishing harbor development, and the execution of coastal engineering projects. • This study tackled a complex challenge in coastal and hydraulic engineering. • The study aimed to understanding nearshore wave and current dynamics and its influence on sediment accretion in tidal inlet. • The Delft 3D model was used to estimate longshore velocity, currents, and sediment transport rates. • The stability assessment of the Muttukadu estuarine inlet was performed. [ABSTRACT FROM AUTHOR]

Sediment associated carbon and nitrogen loss under rainfall, an important cause of soil quality degradation and water eutrophication, strongly depends on the intrinsic properties of original soil types. Relative to total loss, the transport behaviors of organic carbon and nitrogen among sediment size classes and response to soil types remain poorly understood. The concentrations of organic carbon (OC) and total nitrogen (TN) in different sediment size classes (>1, 0.25–1, 0.10–0.25, and <0.10 mm) and their contributions to total sediment load during rainfall erosion were determined under field plot rainfall simulation (at 90 mm h−1) on three contrasting soil types (Luvisol, Alisol and Ferralsol) with increased aggregate stability. During rainfall erosion, the concentrations of OC and TN in total and different sized sediments decreased first and then reached a steady state. The variability of OC and TN concentrations (coefficient of variations in 4.2–53.1% and 6.6–41.9%) among sediment size classes decreased from Luvisol to Ferralsol. Compared to original soils, sediments exhibited larger C/N ratios for Luvisol, and smaller values for Alisol, indicating the more selective transport of labile organic matter for weaker aggregated soils. Among sediment size classes, fine particles (<0.10 mm) accounted 69–88% of total OC and TN losses for Luvisol, and decreased to 30–39% for Ferralsol; and the main transport mechanisms of sediment associated OC and TN shifting from suspension-saltation (<0.10 mm) to rolling (>0.25 mm) with increased aggregate stability. Among original soil properties, inorganic cementing agents (including amorphous iron oxides and clay minerals) showed closer relationships with sediment OC and TN losses (|r| = 0.61–0.89, p < 0.001) than organic matter properties (|r| = 0.55–0.87, p < 0.001), further implying the important role of soil aggregate stability across soil types. This study provides an in-depth understanding on soil carbon and nitrogen losses and their divergent characteristics among soil types deserves consideration in the development of erosion model and land management in agricultural systems. • Variability of OC and TN concentrations among sediment sizes decreased from Luvisol to Ferralsol. • Suspension-saltation (<0.10 mm) dominated OC and TN losses for weak aggregated soils. • Contribution of coarse particles by rolling to OC and TN losses increased with aggregate stability. • Runoff rate, iron oxides and sediment size controlled the loss characteristics of OC and TN. [ABSTRACT FROM AUTHOR]