Search Results (180)

A novel polyurethane (W-OH), namely an eco-friendly hydrophilic polymer, has been widely applied in the field of soil erosion. However, recent research has not revealed the process and mechanisms through which W-OH application influences the soil detachment by concentrated overland flow (hereinafter referred to as soil detachment). In this study, the effects of the W-OH concentration on the physical and mechanical properties and the detachment capacity of colluvial deposit slope soil were investigated, and the impact of the relationship between the flow discharge and the W-OH concentration on the soil detachment capacity was examined under the experimental conditions. The results indicated that W-OH application significantly increased the large-particle content in the soil samples, enhanced the strength properties of the soil samples, reduced their separation capacity, and increased their stability. The structural equation modelling results revealed that W-OH application influences the soil detachment capacity primarily by affecting the shear strength, which exerts a significant negative effect on the detachment capacity (path coefficient = −0.57, p < 0.001). The soil detachment capacity prediction equation, which is based on the flow discharge and W-OH concentration, exhibited satisfactory accuracy (Nash–Sutcliffe efficiency (NSE) = 0.964) and can be used to predict the soil detachment capacity with high precision under similar experimental conditions. In addition, at a W-OH concentration above 1.53%, the impact on the soil detachment capacity is greater than that of the flow discharge. This study focused on investigating the process and mechanisms through which W-OH application reduces soil erosion on colluvial deposit slopes, thereby providing reference data for the management of Benggang erosion. Full article

Gravel coverage on slopes influences overland flow and soil erosion. However, the effect of different gravel sizes on the soil erosion process remains underexplored. In this study, a runoff scour test was performed to examine the effects of gravel coverage on the hydrodynamic characteristics of slope runoff and sediment transport capacity (T_c). The slope gradient varied from 18% to 84%, the unit flow discharge ranged from 0.27 × 10⁻³ to 1.11 × 10⁻³ m² s⁻¹, and gravel coverage was adjusted from 0% to 90%. The results reveal that water depth, shear stress, and stream power increased with gravel coverage. However, once coverage exceeded 20%, flow velocity and unit stream power decreased and stabilized. As gravel coverage increased, the hydraulic regimes transitioned from laminar to turbulent flow and shifted from supercritical to subcritical. Consequently, T_c first increased and then decreased with the increase in gravel coverage, reaching a peak at 20% coverage (1.66 kg m⁻¹ s⁻¹). Moreover, the degree of coverage indirectly influenced T_c through grain shear stress. The new equations, based on the Box–Lucas function, incorporated slope, grain shear stress, and flow velocity, thereby effectively simulating T_c for runoff on gravel-covered slopes (R² = 0.94, NSE = 0.94). These findings provide a basis for modeling soil erosion on gravel-covered slopes. Full article

The mechanism of soil detachment on steep slopes is obviously different from that on gentle slopes. However, the slope effect of soil detachment remains unclear. The objective of this study was to quantify the slope effect of soil detachment capacity at the varying hydrodynamic characteristics. In this study, the soil detachment capacity (Dc) on clay loam and hydrodynamic characteristics were measured by conducting the runoff scouring experiments at 10 slope gradients (1.7–57.7%) and 5 unit flow discharges (0.022–0.089 m²·min⁻¹). The results showed that the relationships between Dc and hydrodynamic parameters were affected by slope gradient. Based on the optimal functional relationship, the hydrodynamic characteristics (flow velocity, flow shear stress, stream power, unit stream power, and unit energy) calculated by maximum and minimum Dc in this study changed by 19.91–95138.10%, and the Dc calculated by the maximum and minimum hydrodynamic characteristics could differ by up to nine orders of magnitude. Overall, the power function of hydrodynamic parameters was superior to the linear function in different slope gradients. The stream power was the best predictor for Dc compared with other hydrodynamic parameters. For all combinations of slope gradients, the adjusted coefficient of determination (Adj. R²) of the power relationship between Dc and stream power was 9.41–27.40% higher than it was between Dc and other hydrodynamic parameters. The coefficient and index of power function for different hydrodynamic parameters showed a trend change with increasing slope gradient, indicating that there was a slope effect on Dc. Further analysis found that Dc could be well predicted using a power combination equation of slope gradient, flow velocity, and flow depth (Adj. R² = 0.96). This study helps to better understand the mechanism of soil detachment and emphasizes that the slope effect should be considered when establishing a soil detachment equation. Full article

The Wadi Haily basin in southwest Saudi Arabia, which runs along the Red Sea coast, serves as an ideal natural laboratory for understanding flash flood dynamics in this region. However, limited morphometric and hydrological data are currently available in this area. This study aims to analyze key morphometric effective parameters to examine and assess flash flood risk potential within the basin. Using remote sensing, GIS, geological, and topographical datasets, this research combines advanced modeling and GIS tools to produce detailed flood hazard maps and risk assessments. This study examines 15 sub-basins of varying sizes, characterized by primary stream orders ranging from 4th to 8th. Based on morphometric analysis, the basins are categorized by flood susceptibility: four basins have a low flood risk, five exhibit moderate risk, and six are highly susceptible to flooding. Key findings indicate that the study area features a vast drainage area, high grid cell values of the drainage frequency, moderate drainage density, elongated basin shapes, low infiltration rates, and long overland flow distances, all suggesting a heightened flood hazard. Additional indicators include high values in gradient ratios, slopes, ruggedness numbers, relief ratios, and basin relief, reinforcing the basin’s flash flood vulnerability. This study provides a comprehensive morphological framework that can support strategic flood management and hazard mitigation planning for the Wadi Haily region. Full article

Ice jamming is the primary mechanism that can generate overland flooding and recharge the isolated basins of the Peace–Athabasca Delta (PAD), a valuable ecosystem of international importance and the ancient homeland of the Indigenous Peoples of the region. Focusing on the regulated Peace River and the Peace Sector of the delta, which has been experiencing a drying trend in between rare ice-jam floods over the last ~50 years, this study describes recent notable breakup events, associated observational data, and numerical applications to determine river discharge during the breakup events. Synthesis and interpretation of this material provide a new physical understanding that can inform the ongoing development of a protocol for strategic flow releases toward enhancing basin recharge in years when major ice jams are likely to form near the PAD. Additionally, several recommendations are made for future monitoring activities and improvements in proposed antecedent criteria for early identification of “promising” breakup events. Full article

A one-dimensional numerical overland flow model based on the cascade plane theory was developed to estimate rainfall-induced runoff and soil erosion on converging and diverging plane surfaces. The model includes three components: (i) soil infiltration using Horton’s infiltration equation, (ii) overland flow using the kinematic wave approximation of the one-dimensional Saint-Venant shallow water equations for a cascade of planes, and (iii) soil erosion based on the sediment transport continuity equation. The model’s performance was evaluated by comparing numerical results with laboratory data from experiments using a rainfall simulator and a soil flume. Four independent experiments were conducted on converging and diverging surfaces under varying slope and rainfall conditions. Overall, the numerically simulated hydrographs and sediment graphs closely matched the laboratory results, showing the efficiency of the model for the tested controlled laboratory conditions. The model was then used to numerically explore the impact of different plane soil surface geometries on runoff and soil loss. Seven geometries were studied: one rectangular, three diverging, and three converging. A constant soil surface area, the rainfall intensity, and the slope gradient were maintained in all simulations. Results showed that increasing convergence angles led to a higher peak and total soil loss, while decreasing divergence angles reduced them. Full article

Time-lapse ground-penetrating radar (GPR) surveys, combined with automated infiltration experiments, provide a non-invasive approach for investigating the distribution of infiltrated water within the soil medium and creating three-dimensional images of the wetting bulb. This study developed and validated an experimental protocol aimed at quantifying and visualizing water distribution fluxes in layered soils under both unsaturated and saturated conditions. The 3D images of the wetting bulb significantly enhanced the interpretation of infiltration data, enabling a detailed analysis of water movement through the layered system. We used the infiltrometer data and the Beerkan Estimation of Soil Transfer parameters (BEST) method to determine soil capacitive indicators and evaluate the physical quality of the upper soil layer. The field survey involved conducting time-lapse GPR surveys alongside infiltration experiments between GPR repetitions. These experiments included both tension and ponding tests, designed to sequentially activate the soil matrix and the full pore network. The results showed that the soil under study exhibited significant soil aeration and macroporosity (represented by AC and p_MAC), while indicators related to microporosity (such as PAWC and RFC) were notably low. The RFC value of 0.55 m³ m⁻³ indicated the soil’s limited capacity to retain water relative to its total pore volume. The PAWC value of 0.10 m³ m⁻³ indicated a scarcity of micropores ranging from 0.2 to 30 μm in diameter, which typically hold water accessible to plant roots within the total porosity. The saturated soil hydraulic conductivity, K_s, values ranged from 192.2 to 1031.0 mm h⁻¹, with a mean of 424.4 mm h⁻¹, which was 7.9 times higher than the corresponding unsaturated hydraulic conductivity measured at a pressure head of h = −30 mm (K₋₃₀). The results indicated that the upper soil layer supports root proliferation and effectively drains excess water to the underlying limestone layer. However, this layer has limited capacity to store and supply water to plant roots and acts as a restrictive barrier, promoting non-uniform downward water movement, as revealed by the 3D GPR images. The observed difference in hydraulic conductivity between the two layers suggests that surface ponding and overland flow are generated through a saturation excess mechanism. Water percolating through the soil can accumulate above the limestone layer, creating a shallow perched water table. During extreme rainfall events, this water table may rise, leading to the complete saturation of the soil profile. Full article

This study investigated the impact of thinning and felled logs (random- and contour-felled logs) on overland flow, soil erosion, and litter erosion in a Japanese cypress forest plantation (2400 tree ha⁻¹) with low ground cover, from 2018 to 2023 in central Japan. Monthly measurements of overland flow and soil and litter erosion were carried out using small-sized traps across three plots (two treatments and one control). In early 2020, a 40% thinning (tree ha⁻¹) was conducted in the two treatment plots. Overland flow increased in the plot with random-felled logs during the first year post-thinning (from 139.1 to 422.0 L m⁻¹), while it remained stable in the plot with contour-felled logs (from 341.8 to 337.1 L m⁻¹). A paired-plot analysis showed no change in overland flow in the contour-felled logs plot compared to the control plot from the pre- to post-thinning periods (pre-thinning Y = 0.41X − 0.69, post-thinning Y = 0.5X + 5.46, ANCOVA: p > 0.05). However, exposure to direct rainfall on uncovered ground areas post-thinning led to increased soil and litter erosion in both treatment plots. These findings suggest that thinning combined with contour-felled logs effectively stabilizes overland flow. Therefore, thinning with contour-felled logs can be considered a viable method for mitigating overland flow in monoculture plantations with low ground cover. Full article

To provide accurate and efficient forecasting of fluvial flooding assessment in the river basin, the present study links the well-known CA-based urban inundation modeling (2D-OFM-CA) with a one-dimensional river flow model (1D-RFM) as a coupled 1D-2D river–overland modeling. Rules to delineate the geometric linking between the 1D-RFM and 2D-OFM-CA along embankments are developed. The corresponding exchanged water volume across an embankment is then computed by using the free and submerged weir flow formulas. The applicability of the proposed coupled model on fluvial flooding assessment is then assessed and compared with a well-recognized commercial software (HEC-RAS model) through an idealized fluvial case and an extensively studied real-scale fluvial case in the Severn River Basin. Based on the simulated results concerning the numerical accuracy, the coupled model is found to give similar results in the aspects of the river flow and overland flow modeling in both two study cases, which demonstrates the effectiveness of the linking methodology between the 1D-RFM and 2D-OFM-CA. From the viewpoint of numerical efficiency, the coupled model is 47% and 41% faster than the HEC-RAS model in the two cases, respectively. The above results indicate that the coupled model can reach almost the same accuracy as the HEC-RAS model with an obvious reduction in its computational time. Hence, it is concluded that the coupled model has considerable potential to be an effective alternative for fluvial flooding assessment in the river basin. Full article

We developed a spatiotemporal mapping approach utilizing multiple techniques for distinguishing and mapping known reclaimed mine sites from “unreclaimed” mine sites in a historic uranium mining district along the South Texas Coastal Plains. Lidar laser scanning penetrates the vegetation canopy to expose anthropogenic modifications to the landscape. The Lidar analysis (bare earth elevation surface, slope, topographic contours, topographic textures, and overland-flow hydrography) revealed mine features. Visual interpretation of Landsat imagery and time-series analysis augmented the Lidar analysis revealing the temporal life cycle of mining. The combination of bare earth texture with time-lapse and time-series analyses revealed areas of disturbance for reclaimed mines. The spatiotemporal mapping approach proved to be most useful in identifying and characterizing the known mine pit and pile features, reclamation status, and areas of disturbance due to mining. Two mine waste volume estimation methods resulted in a 21% difference indicating that although the approach helps to map mine features and areas of mining disturbance for the purposes of mine land inventory, additional information is needed to improve the estimation of buried mine waste at reclaimed mine sites. Full article

There has been an increase in the frequency of hazards associated with meteorological and hydrological phenomena. One of them is flash floods occurring episodically in areas of concentrated runoff—valleys without permanent drainage. In the opinion of residents and local authorities, these are potentially safe areas—they are not threatened by floods and are therefore often occupied by buildings. The importance of addressing flash floods in land use planning is essential for sustainable development and disaster risk reduction. The objective of this research was to assess the level of the hazard and to evaluate its presence in land use planning activities. This manuscript fills a research gap, as to date flash flood threats have not been analyzed for individual buildings located in catchments of dry valleys in temperate climates. More than 12,000 first-order catchments were analyzed. The study covered an upland area located in East Poland, which is characterized by high population density and dispersed rural settlement. Within the 10 municipalities, buildings located on potential episodic runoff lines were identified. Qualitative assessment was applied to ascertain the susceptibility of catchments to flash floods. Such criteria as slopes, size, shape of the catchment area, and land cover, among others, were used. Between 10 and 20% of the buildings were located on episodic runoff lines, and about 900 sub-catchments were highly or very highly susceptible to flash floods. The way to reduce the negative effects of these phenomena is to undertake proper land use planning based on knowledge of geohazards, including flash floods. However, an analysis of available planning documents shows that phenomena of this type are not completely taken into account in spatial management processes. Full article

Hydrodynamic models are often used to obtain insights into potential dike breaches, because dike breaches can have severe consequences. However, their high computational cost makes them unsuitable for real-time flood forecasting. Machine learning models are a promising alternative, as they offer reasonable accuracy at a significant reduction in computation time. In this study, we explore the effectiveness of a Long Short-Term Memory (LSTM) neural network in fast flood modelling for a dike breach in the Netherlands, using training data from a 1D–2D hydrodynamic model. The LSTM uses the outflow hydrograph of the dike breach as input and produces water depths on all grid cells in the hinterland for all time steps as output. The results show that the LSTM accurately reflects the behaviour of overland flow: from fast rising and high water depths near the breach to slowly rising and lower water depths further away. The water depth prediction is very accurate (MAE = 0.045 m, RMSE = 0.13 m), and the inundation extent closely matches that of the hydrodynamic model throughout the flood event (Critical Success Index = 94%). We conclude that machine learning techniques are suitable for fast modelling of the complex dynamics of dike breach floods. Full article

Wildfires significantly influence the environmental distribution of various elements through their fire-induced input and mobilization, yet little is known about their effects on the forest floor in Siberian forests. The present study evaluated the effects of spring wildfires of various severities on the levels of major and minor (Ca, Al, Fe, S, Mg, K, Na, Mn, P, Ti, Ba, and Sr) trace and ultra-trace (B, Co, Cr, Cu, Ni, Se, V, Zn, Pb, As, La, Sn, Sc, Sb, Be, Bi, Hg, Li, Mo, and Cd) elements in the forest floors of Siberian forests. The forest floor (Oi layer) samples were collected immediately following wildfires in Scots pine (Pinus sylvestris L.), larch (Larix sibirica Ledeb.), spruce (Picea obovata Ledeb.), and birch (Betula pendula Roth) forests. Total concentrations of elements were determined using inductively coupled plasma–optical emission spectroscopy. All fires resulted in a decrease in organic matter content and an increase in mineral material content and pH values in the forest floor. The concentrations of most elements studied in a burned layer of forest floor were statistically significantly higher than in unburned precursors. Sb and Sn showed no statistically significant changes. The forest floor in the birch forest showed a higher increase in mineral material content after the fire and higher levels of most elements studied than the burned coniferous forest floors. Ca was a predominant element in both unburned and burned samples in all forests studied. Our study highlighted the role of wildfires in Siberia in enhancing the levels of geochemical elements in forest floor and the effect of forest type and fire severity on ash characteristics. The increased concentrations of elements represent a potential source of surface water contamination with toxic and eutrophying elements if wildfire ash is transported with overland flow. Full article

The concept of watersheds, also called catchments, is fundamental to both flood mitigation and water resource management, as it greatly aids in the calculation of overland flow attributes. Watershed boundaries are typically determined by elevation, as water adheres to the geological characteristics of watersheds under natural circumstances and does not cross watershed boundaries. However, advances in human development have caused elevation and land usage changes, and boundaries between adjacent watersheds in downstream areas with flat terrain have become unclear and unstable. This study chose the Kaoping River watershed and Donggang River watershed as the study area, to investigate the cross-watershed runoff phenomenon under different return period rainfall. Based on land use surveys of the study area, the area in proximity to the boundary between the two watersheds was highly developed, with land primarily used for agriculture, buildings, and transportation. As the study area was highly developed, cross-watershed runoff was observed, even in the 2-year return period rainfall simulation case. The size and depth of the areas where cross-watershed runoff occurred became stable in the simulation cases, with return periods of 25 years or greater due to the surrounding high-elevation terrain obstructing further surface runoff development. Thus, when planning for flood mitigation, cross-watershed runoff from adjacent watersheds must also be considered, in addition to normal surface runoff. Full article

Soil erosion by water on agricultural hillslopes leads to numerous environmental problems including reservoir sedimentation, loss of agricultural land, declines in drinking water quality, and requires deep understanding of underlying physical processes for better mitigation. It is imperative to accurately predict soil erosion caused by overland flow processes so that soil conservation efforts can be undertaken proactively before large-scale sedimentation problems arise. Soil detachment is often described by the excess shear stress equation that contains two physical soil erodibility parameters, erodibility coefficient, and critical shear stress. These parameters are normally assumed to be constant but can change across varying soil texture classes as well as during surface runoff events due to changes in soil cohesion and potential dependency on soil moisture content. These changes may significantly affect soil erosion rates at the field and watershed scale. In this study, the erodibility parameters of three soil types (sandy loam, clay loam, and silty clay loam) were analyzed using a laboratory mini-Jet Erosion Test (JET) to determine the effect of soil sample infiltration and moisture condition. Results from the experiments depicted a dynamic relationship between the soil erodibility parameters and amount of infiltrated mass of water. Data analysis displayed that for soils of different texture critical shear stress exhibited local minimum with higher values for very dry and saturated soils, while erodibility coefficient tended to increase with the increase of mass of soil water. Utilizing these dynamic soil erodibility parameters did not result in a significant difference in soil erosion rates when compared to using the averaged soil erodibility parameters taken from the experiment but the range of potential erosion rates increases with the increase of applied sheer stress to soil surface. The erosion rates with the experiment-based coefficients were found to be higher than with the baseline WEPP-based coefficients. These results highlight the importance of evaluating the effect of intrastorm dependent factors during surface runoff events, such as antecedent soil moisture content, time to peak from the start of runoff, soil cohesion, etc., on soil erodibility parameters to accurately calculate erosion rates, especially for initially dry soils or during earlier stages of surface runoff when critical shear stresses were highly affected. Further assessment of such factors with JET or other laboratory and field tests is recommended. Full article