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Soil erosion is a major problem around the world because of its effects on soil productivity, nutrient loss, siltation in water bodies, and degradation of water quality. By understanding the driving forces behind soil erosion, we can more easily identify erosion-prone areas within a landscape to address the problem strategically. Soil erosion models have been used to assist in this task. One of the most commonly used soil erosion models is the Universal Soil Loss Equation (USLE) and its family of models: the Revised Universal Soil Loss Equation (RUSLE), the Revised Universal Soil Loss Equation version 2 (RUSLE2), and the Modified Universal Soil Loss Equation (MUSLE). This paper reviews the different sub-factors of USLE and RUSLE, and analyses how different studies around the world have adapted the equations to local conditions. We compiled these studies and equations to serve as a reference for other researchers working with (R)USLE and related approaches. Within each sub-factor section, the strengths and limitations of the different equations are discussed, and guidance is given as to which equations may be most appropriate for particular climate types, spatial resolution, and temporal scale. We investigate some of the limitations of existing (R)USLE formulations, such as uncertainty issues given the simple empirical nature of the model and many of its sub-components; uncertainty issues around data availability; and its inability to account for soil loss from gully erosion, mass wasting events, or predicting potential sediment yields to streams. Recommendations on how to overcome some of the uncertainties associated with the model are given. Several key future directions to refine it are outlined: e.g. incorporating soil loss from other types of soil erosion, estimating soil loss at sub-annual temporal scales, and compiling consistent units for the future literature to reduce confusion and errors caused by mismatching units. The potential of combining (R)USLE with the Compound Topographic Index (CTI) and sediment delivery ratio (SDR) to account for gully erosion and sediment yield to streams respectively is discussed. Overall, the aim of this paper is to review the (R)USLE and its sub-factors, and to elucidate the caveats, limitations, and recommendations for future applications of these soil erosion models. We hope these recommendations will help researchers more robustly apply (R)USLE in a range of geoclimatic regions with varying data availability, and modelling different land cover scenarios at finer spatial and temporal scales (e.g. at the field scale with different cropping options).

Siltation is one of the main aggravating factors for floods in urbanized basins, altering flow capacity and increasing socio-environmental risks. This study evaluates the impacts of siltation on flood dynamics in the Jundiaí River Basin (São Paulo, Brazil), using hydrodynamic modeling (HEC-RAS 6.0) and the Hazard Index (HI = y × v), based on hydraulic thresholds established in the literature. Three scenarios were simulated for an extreme 100-year return period (RP) event: (1) reference condition (no siltation), (2) moderate siltation (20% reduction in depth), and (3) severe siltation (40% reduction). The results indicated three distinct hydrodynamic behavior patterns: high-energy zones (where the cross-section reduction increased velocity and erosive power), active deposition zones (locations with low velocity, v < 0.3 m/s, with lateral flood expansion), and transition areas (with unstable Hazard Index behavior). An increase in the flooded area was observed by 12% (moderate scenario) and 28% (severe scenario), with a critical rise in the HI (> 4.0 m²/s) in high hydraulic energy zones, while low-velocity areas (v < 0.3 m/s) showed lateral flood expansion. Sediment deposition was predominant in floodplains and reaches with slopes < 0.3%, corroborating literature studies. It is concluded that siltation not only expands the flooded area but also intensifies hydrodynamic risks in critical regions, demanding integrated sediment management strategies. Keywords: hazard index, hydrodynamic modeling, Jundiaí River, siltation.

To materialize the inherent opportunities of incoming sediment load, various interventions are being practiced for sediment management in rivers and delta systems. Broadly, the practiced methods can be divided into two categories: (i) management for accelerating siltation to enhance land reclamation and counterbalancing bank erosion (ii) management for de-siltation in the channels to maintain required navigational flow depth. The prerequisites for achieving the above targets at the same time are quite contradictory, as land reclamation requires more sediment, while maintaining navigational depth requires less sediment load. To address the aforementioned constraints, Bandal-like Structures (BLS), an indigenous nature-based solution, has proposed for redistributing the local flow-sediment regime to create a sediment deficit zone within the river side and a sediment surplus zone along the bankside, which can eventually be useful for the maintenance of navigational channels as well as bank stabilization. Based on research conducted over the last 20 years, this article discusses BLS's experiences in achieving both functions simultaneously. A well-documented case study of its application along a reach of the braided Jamuna River is one of many implemented BLS at various scales in the Ganges-Jamuna-Brahmaputra (GBM) system. Based on the performance of the implemented case study and existing indigenous knowledge, a hybrid approach integrating conventional and community sciences is proposed as a nature-based solution for sustainable sediment management in Bangladesh's river systems.

The loess hilly area consists of a slope–gully system, which promotes erosion; as such. it is one of the most intensely eroded areas in the world. The construction of check dams can effectively control water and soil loss of slope gullies. However, existing studies focus on the benefits of intercepting runoff and sediments at dam sites, while ignoring the change law of hydrological processes with respect to progressing dam land sedimentation. Moreover, past studies focus on the “runoff–sediment” or “flood–sediment” relationships, but rarely consider the “hydrodynamics–runoff” and “hydrodynamics–sediment” dynamics. Therefore, in this study, we developed five physical models of slope–gully systems for dam land sedimentation depths of 0, 1, 2, 3, and 4 m, in order to explore the effects of sedimentation on runoff–sediment–hydrodynamic processes. The runoff and sediment yield of the slope–gully system decreased with increasing siltation depth. The spatial and temporal distributions of the hydrodynamic parameters were different. The Reynolds number (Re), runoff energy consumption (ΔE), and runoff power (P) increased with rainfall time, whereas runoff shear stress (τ) and Froude number (Fr) did not show a significant trend over time. Re and ΔE could better describe the runoff process of the slope–gully system, while P and ΔE could better simulate the sedimentation process. Notably, our study can provide a scientific basis for establishing effective erosion prediction models to estimate the water erosion process of slope–gully systems.

The performance of urban drainage systems can be significantly compromised by siltation in pipeline networks. This study focuses on the drainage network of central Zhengzhou, analyzing operational risks under current siltation conditions. Using complex network theory, the study examines the structural characteristics and propagation mechanisms of the siltation propagation chain, quantifying node risks through indicators such as pipeline risk factors and degree centrality. Edge vulnerability is incorporated to evaluate the risk values of siltation propagation paths. The study’s findings indicate the following: (1) Despite a relatively low overall siltation risk, regular pipeline inspection and maintenance is necessary. (2) A total of 22 critical nodes, primarily located in main pipelines or confluence manholes, exhibit high risk and require priority attention. (3) Siltation propagation shows significant chain characteristics, with main pipeline and junction node failures potentially leading to systemic crises. In the central Zhengzhou stormwater network presented in this paper, high-risk factors are concentrated in a southern downstream outlet caused by an edge identified as critical that propagates siltation risks to the downstream nodes, forming a long path with elevated risk levels. This study provides crucial insights into the risk management and prevention of sedimentation and blockages in urban drainage networks, not only offering important technical references and a solid scientific basis for pipeline maintenance and network upgrades—thereby contributing to drainage system planning and the enhancement of urban flood protection capabilities—but also serving as a valuable technical reference for improving the overall resilience and operational efficiency of drainage systems.

The middle Paraíba do Sul River region represents Brazil’s most industrialized area, where the largest steel industry in the country, the National Steel Company (Companhia Siderúrgica Nacional—CSN) is located. The Light hydropower complex is located downstream from the CSN and, in the present study, four sediment cores samples were collected at the Vigário Reservoir, one of the seven reservoirs existing in this complex. The reservoir region has suffered huge transformations since its implementation and CSN construction, enhancing reservoir siltation. Despite this, bathymetric surveys are scarce, with only two carried out in seventy years, making siltation process changes along this period unknown. To obtain this information, 210Pb dating was applied. Based on porosity profiling, three cores were selected for 210Pb dating, only the core sampled near the water inflow was considered not suitable for 210Pb dating. The same results in the three sediment cores were noted, with an increasing sediment accumulation rate (SAR), from 0.6 cm y−1 originally to 2.9 cm y−1 currently. Chromium and zinc, both associated to CSN activities, presented a trend toward lower values during the last twenty years, attributed to the implementation of the ISO 14001 policy at the CSN. Chromium reached concentrations higher than the probable effect level (PEL), before 2000, although actual values were close to the threshold effect level (TEL). Mercury concentration variations were attributed to sediment granulometry changes due to land use transformations, and not to eventual illegal gold mining activities along the middle of the Paraiba do Sul River.

Han, Z.; Li, H.; Xie, H.; Yang, H.; Ouyang, Q., and Gong, S., 2022. Dredging of the Shenzhen-Zhongshan Link in the Pearl River Estuary, China: Short-term siltation mechanism for a trial trench. Journal of Coastal Research, 38(5), 988–998. Coconut Creek (Florida), ISSN 0749-0208. Understanding the short-term, particularly daily, siltation mechanism of a dredged trench is critical for immersed tunnel construction, as well as for offshore engineering and coastal management. This study explored the short-term siltation mechanism of the trial trench dredged for the Shenzhen-Zhongshan Link in the Pearl River Estuary, China. Monthly silting characteristics over a period of ∼11 months indicate that the silting intensity during the flood season was much larger than during the dry season. Local suspended sediment concentrations (SSCs) also varied on a flood–dry seasonal cycle, which were impacted by the suspended load from the Pearl River. Daily silting characteristics indicate that the silting intensity during spring tides were higher than during neap and moderate tides and that the local SSCs and flow velocities also varied on a spring–neap tidal cycle, which was dominated by periodic variations in the astronomical tide. The flow velocity deceased substantially from the surface to the bottom of the trench, and flow circulation occurred at the bottom of the trench, which aided the silting process. Seasonal changes in the sediment load from the Pearl River were the dominant cause of the changes in suspended sediment around the trench, which produced seasonal siltation changes in the trench. Daily changes in trench siltation were directly caused by the amount of sediment that entered the trench, which was affected by changes in the flow velocity and bottom SSC around the trench during the neap–spring tidal cycle. Although the high-siltation intensity during the flood season was unhelpful, the low-siltation intensity during neap and moderate tides was helpful for the construction of immersed tunnel during the flood season.

Soil loss by erosion processes is one of the largest challenges for food production and reservoir siltation around the world. Information on sediment, nutrients and pollutants is required for designing effective control strategies. The estimation of sediment sources is difficult to get using conventional techniques, but sediment fingerprinting is a potentially valuable tool. This procedure intends to develop methods that enable to identify the apportionment of sediment sources from sediment mixtures. We developed a new tool to quantify the provenance of sediments in an agroforest catchment. For the first time, the procedure for the selection of the best combination of tracers was included in the tool package. An unmixing model algorithm is applied to the sediment samples to estimate the contribution of each possible source. The operations are compiled in an R package named FingerPro, which unmixes sediment samples after selecting the optimum set of tracers. An example from a well-studied Mediterranean catchment is included in the package to test the model. The sediment source apportionments are compared with previous results of soil redistributions where 137Cs derived rates validate the unmixing results, highlighting the potential of sediment fingerprinting for quantifying the main sediment provenance. Fingerprinting techniques will allow us to better comprehend sediment transport to water ecosystems and reservoirs and its detrimental effect on the quality of the water and aquatic habitats. The FingerPro package provides further understanding of the unmixing procedure through the use of graphical and statistical tools, offering a broader and easier application of the technique.

Floods are one of the frequent natural hazards occurring in Kerala because of the remarkably high annual rate of rainfall. The objective of this study is to prepare the flood susceptibility maps of Ernakulam district by integrating remote sensing data, GIS, analytical hierarchy process (AHP), and fuzzy-analytical hierarchy process methods. Ernakulam is one of Kerala's most flood-prone districts. The development of this map can help to raise awareness about the risks of flooding. Factors such as slope angle, soil types (texture), land use/land cover, stream density, water ratio index, normalized difference built-up index, topographic wetness index, stream power index, aspect, and sediment transport index have been selected. The area of the final maps is grouped into five flood susceptible zones, ranging from very low to very high. The major reasons for flood occurrence in Ernakulam district are the combined effect of multiple factors such as excess silting, reduction of stream width due to anthropogenic activities, and changes in land cover and land-use pattern, lower slope, higher soil moisture content, lower stream capacity, and poor infiltration capacity of soils. The prepared map was validated using the receiver operating characteristic (ROC) curve method. The area under the ROC curve (AUC) values of 0.75 and 0.81 estimated by the ROC curve method for the AHP and F-AHP methods are considered acceptable and excellent, which confirms the prediction capability of the prepared maps. The very high susceptible zone constitutes around 19% of the district. This map is useful for land-use planners and policymakers to adopt strategies that will reduce the impact of flood hazards and damage in the future.

Mangrove forest is one of the most important ecological and environmental resources by effectively promoting tidal flat deposition and preventing the coastal region from typhoon. However, there have been mass loss of mangrove forests due to anthropogenic activities. It is an urgent need to explore an effective way for mangrove restoration. Here, three rows of bamboo fences with hydro-sedimentary observation set over Aegiceras corniculatum mangrove tidal flat of the Nanliu Delta, the largest delta of Beibu Gulf, China, were conducted to analyze the hydro-sedimentary variations induced by bamboo fences. Results identified that the mean horizontal velocity U m per burst (20 min) decreased by as much as 71% and 40% in comparison with those without bamboo fences in March and November, respectively, when the tidal current entering the bamboo area during flood. The maximum of mean horizontal flow velocity U m-max at bamboo area was 50%–75% of that without bamboo fences during ebb tide. The suspended sediment concentration of bamboo area suggested a maximum reduction of 57% relative to bare flat during flood, and was 80% lower than bare flat at ebb peak. Moreover, the turbulent kinetic dissipation ε at flood tide was significantly higher than that at ebb tide, while the bamboo fences greatly increased the turbulent kinetic dissipation ε by 2 to 5 times relative to bare flat, resulting in an increase of the bed elevation by inhibiting the sediment incipient motion and intercepting suspended sediment. The siltation rate at the bamboo area was 140% and 29.3% higher than that at the bare flat and the region covered with A. corniculatum , respectively. These results highlight that bamboo fences can effectively attenuate tidal current and thus promote siltation over mangrove flat, which contribute great benefit to mangrove survival.