Search Results (608)

The increasing frequency and intensity of extreme climate events have posed more geohazards worldwide. It is therefore crucial to quantify and map risk to reduce disaster-related losses. The main objective of this study is to propose a quantitative framework to conduct risk assessment of buildings and infrastructures impacted by geohazards. A debris flow hazard in Tianjin, North China was taken as a case study. A physically based model and the Gumbel extreme value distribution were utilized to construct a range of extreme rainfall and runoff scenarios. The FLO-2D and ABAQUS software were subsequently employed to simulate the surging behavior of the debris flow and assess the structural vulnerability of buildings, respectively. Furthermore, the number of elements at risk and economic values were estimated to generate risk maps. The results revealed that variations in peak discharge in the channel evidently affected flow velocity and depth, thus elevating the debris flow intensity and the likelihood of the materials threatening buildings. The stiffness degradation of concrete was strategically used as the indicator to quantify structure vulnerability and effectively present the dynamic responses under the impacts of the debris flow. Under a 100-year return period rainfall scenario, the proportion of very high- and high-risk areas reached 31%, with the estimated economic loss approximately ¥167.7 million. This highlighted the critical role that extreme rainfall played in shaping both the spatial distribution and severity of debris flow risks. The proposed method provides a scientific basis for enhancing the resilience of mountainous regions to compound natural disasters exacerbated by climate change. Full article

To clarify the differences in and mechanisms of soil detachment before and after soil collapse, five typical granite soil layers (red soil, red soil–sandy soil, sandy soil, sandy soil–debris, and debris layers) of Benggang in Anxi County, Fujian Province, were studied via laboratory runoff scouring tests, and the detachment capabilities and influencing factors of undisturbed (original) and disturbed (colluvial deposit) soils were compared. The results showed that disturbance due to soil collapse significantly increases the soil detachment capacity by an average of 1046 times, with the greatest increase occurring in the red soil–sand soil layer (3494 times) and the smallest increase occurring in the debris layer (63 times). The undisturbed soil detachment capacity increases with increasing soil depth, whereas the disturbed soil capacity first increases but then decreases, with the sand layer having the highest capacity. Hydrodynamic fitting results revealed that undisturbed red soil has a linear relationship, red soil–sandy soil and sandy soil layers have power function relationships, and sandy soil–debris and debris layers have logarithmic relationships with flow shear stress. Disturbed red soil and red soil–sandy soil layers are linearly related, whereas the other layers are logarithmically related. Correlation analysis revealed that undisturbed soil detachment is significantly negatively correlated with clay, silt, gravel, free iron oxide, and free alumina contents and positively correlated with sand content. Disturbed soil shows similar correlations, but it has a negative correlation with organic matter instead of gravel. Structural equation modelling (SEM) path analysis revealed that undisturbed soil detachment is affected mainly by negative free alumina oxide content (path coefficient of −0.87) and flow shear stress (path coefficient of 0.14), whereas disturbed soil is controlled mainly by negative shear strength (path coefficient of −0.76) and positive flow shear stress (path coefficient of 0.49). This study elucidates the mechanism by which colluvial deposit disturbance accelerates soil detachment, providing a theoretical basis for the prevention and control of Benggang erosion in the hilly regions of southern China with red soil. Moreover, the comparative research strategy adopted in this study offers a reference for related investigations in similar erosion-prone areas. Full article

Rapid urbanization has led to increasing structural modification of river catchments through dam construction and concrete-lining of natural channels as flood management measures. These interventions can alter the natural hydrology. This necessitates assessment of their influence on hydrology at a catchment scale. However, such evaluations are particularly challenging in data-scarce regions such as the Chongwe River Catchment, where hydrometric records capturing conditions before and after structural modifications are limited. Therefore, we applied a 2D rain-on-grid approach in HEC-RAS to evaluate changes in high-flow responses to short-duration, high-intensity rainfall events in the Chongwe River Catchment in Zambia, where structural interventions have been implemented. The terrain was modified in HEC-RAS to represent 21 km of concrete drains and ten dams. Sensitivity analysis conducted on five key model parameters showed that parameters controlling surface runoff generation, particularly curve number, exerted the strongest influence on simulated peak flows, while routing-related parameters had a secondary effect. Model calibration and validation showed strong performance with R² = 0.99, NSE = 0.75 and PBIAS = −0.68% during calibration and R² = 0.95, NSE = 0.75, PBIAS = −2.49% during validation. Four scenarios were simulated to determine the hydrological effects of channel concrete-lining and dams. The results showed that concrete-lining of natural channels in the urban area increased high flows at the main outlet by approximately 4.6%, generated localized instantaneous maximum channel velocities of up to 20 m/s, increased flood depths by up to 11%, decreased lag times and expanded flood inundation widths by up to 15%. The existing dams reduced peak flows by about 28%, increased lag times, reduced flood depths by about 11%, and reduced flood inundation widths by up to 8% across the catchment. The findings demonstrate that enhancing stormwater conveyance through concrete-lining must be complemented by storage to manage high flows, while future work should explore nature-based solutions to reduce channel velocities and improve sustainable flood mitigation. Therefore, the study provides event-scale insights to support flood-risk management and infrastructure planning in rapidly urbanizing, data-scarce catchments. Full article

This article provides a comprehensive analysis of long-term changes in the minimum river flow of the southern rivers of Western Kazakhstan (Temir, Oiyil, Zhem) for the period 1940–2022, with an emphasis on summer minimum and winter low flow as key indicators of water and environmental sustainability in conditions of increasing climate variability. The study combines a typology of the climate control mechanisms of minimum flow, analysis of structural homogeneity, and assessment of the internal organization of time series based on ITA and the integral IPTA method, which allow us to reveal the hidden fluctuations and stable phase states of the hydrological regime. The calculation of the climate sensitivity index (CSI_min) showed pronounced seasonal asymmetry: summer runoff is largely controlled by atmospheric precipitation, while winter minimum runoff is determined by temperature regime and soil freezing depth. Parametric and nonparametric tests (Pettitt, ADF, SNHT) revealed significant structural shifts in the 1960s–1990s period, corresponding to large-scale climatic anomalies in the region. Summer series are characterized by phases of prolonged low water levels and negative trends in the mid-20th century, while for the winter period, a steady increase in minimum flow has been established, due to regional warming and an increase in the share of underground recharge. IPTA confirmed the presence of long-term phases with high internal heterogeneity in the summer season and a more stable winter runoff structure. The results demonstrate the high climatic sensitivity of minimum runoff and confirm the need to move from static standards to dynamically adaptable methods of water resource assessment. The proposed approach can serve as a tool for developing adaptation strategies, assessing the risk profile of basins, and improving the sustainability of water management planning in arid regions. Full article

A typical Tamarix nebkha was studied in the southern Qaidam Basin, China. K-feldspar pIRIR dating was applied to establish a reliable chronological framework, and an Undatable age–depth model was constructed. Accumulation rates (AR) declined in stages: rapid (~1.33 cm/a; ~370–260 yr BP), slower (~0.75 cm/a; ~260–130 yr BP), and slowest (~0.31 cm/a; ~130 yr BP-present). This dynamic pattern is likely influenced by a combination of regional aeolian activity variations, geomorphological evolution, and the intrinsic growth dynamics of the nebkha itself. To further understand the relationship between nebkha development and climatic conditions, a δ¹³C sequence was reconstructed using Tamarix plant remains preserved within the sediments. Based on shifts in leaf-level δ¹³C values, which indicate changes in water use efficiency, water availability over the past 370 years was inferred and divided into three main phases: relatively sufficient from 1650 to 1690, gradually decreasing during 1690–1870, and increasing again after 1870. The δ¹³C trend closely correlates with temperature variations derived from δ¹⁸O records of the Malan ice core. This suggests that in this hyper-arid region, the development of Tamarix nebkhas is primarily controlled by glacial meltwater and snowmelt runoff from the Kunlun Mountains, rather than by local precipitation. Full article

The application of two-dimensional (2D) hydrologic and hydraulic modeling tools is increasing for overland flow simulation, as they represent spatial changes in depth, velocity, and flow conditions more accurately. Recently, the US Army Corps HEC-HMS (Hydrologic Engineering Center Hydrologic Modeling System) added the capability to import an unstructured 2D mesh, which enables the routing of excess precipitation across the mesh, as a fully distributed hydrological model. In HEC-HMS, the 2D diffusion-wave component functions as a hydrologic transform representing overland flow routing. In contrast, HEC-RAS 2D (Hydrologic Engineering Center-River Analysis System), initially applied to river flow simulation, can apply either the 2D shallow-water equations or the 2D diffusion-wave option. Similarly to HEC-HMS, HEC-RAS also includes rain-on-grid (RoG) capability and infiltration algorithms, and in this fashion has some hydrological modeling capabilities. Still, while HEC-HMS is capable of representing extended-period hydrological simulations, HEC-RAS hydrological capabilities are limited to event-based simulations, as there are no provisions to represent abstractions such as evapotranspiration or groundwater/baseflow contributions together. Studies performing a direct comparison between the HEC-HMS RoG and HEC-RAS RoG approaches for representing urban hydrology remain scarce. This study aims to fill that gap by assessing their performance in Moore’s Mill Creek Watershed, in Lee County, Alabama, with a focus on continuous rainfall-runoff modeling. Both models run on the same unstructured mesh and use identical rainfall, terrain, land-use, and soil data. Model simulations are compared over an extended period to evaluate simulated depth, velocity, and flow hydrographs against field observations. The comparison shows HEC-HMS’s superior performance for extended simulation and provides practical guidance on parameter alignment, data needs, and tool selection. Full article

Urban underpasses are critical flood-prone hotspots during extreme rainfall, posing significant threats to urban resilience and infrastructure safety. However, a scale gap persists between catchment-scale hydrological models, which often oversimplify local geometry, and high-fidelity hydrodynamic models, which typically lack realistic boundary conditions. To bridge this gap, this study develops a multi-scale framework that integrates the Storm Water Management Model (SWMM) with 3D Computational Fluid Dynamics (CFD). The framework employs a unidirectional integration (one-way forcing), utilizing SWMM-simulated runoff hydrographs as dynamic inlet boundaries for a detailed CFD model of a 2.8 km underpass in Shanghai. Simulations across six design rainfall events (2- to 50-year return periods) revealed two distinct flooding mechanisms: a systemic response at the hydraulic low point, governed by cumulative inflow; and a localized response at entrance concavities, where water depth is rapidly capped by micro-topography. Informed by these mechanisms, an intensity-graded drainage strategy was developed. Simulation results show significant differences between different drainage strategies. Through this framework and optimized drainage system design, significant water accumulation within the underpass can be prevented, enhancing its flood resistance and reducing the severity of disasters. This integrated framework provides a robust tool for enhancing the flood resilience of urban underpasses and offers a basis for the design of proactive disaster mitigation systems. Full article

This study proposes a framework, the RA_WLTE_River model, for quantifying the reliability of flood-altering water-level thresholds, considering rainfall and runoff-related uncertainties. The Keelung River in northern Taiwan is selected as the study area, and associated hydrological data from 2008 to 2016 are applied in the development and application of the model. According to the results from the model development and demonstration, the average and maximum rainfall intensities, roughness coefficients, and maximum tide depths exhibit a significant contribution to the reliability quantification of the estimated water-level thresholds. In addition, empirically based water-level thresholds can achieve the goal of rainfall-induced flood early warning, with a high likelihood of nearly 0.95. Additionally, the probabilistically based water-level thresholds derived from the described reliability can efficiently ensure consistent flood early warning performance at all control points along the river. Full article

This study investigates flow resistance in thin water films on road surfaces during rainfall, which is essential for assessing aquaplaning risk. A one-dimensional surface runoff model based on the diffusion-wave approach is used to compare existing equations for the Darcy–Weisbach friction factor and Manning’s roughness coefficient. Laboratory data from three experimental cases support the analysis. The first case assesses the accuracy of existing equations and develops a new regression-based equation. The second case validates this new model for predicting water film thickness. Findings show that many existing equations poorly estimate water film thickness under high-intensity rainfall conditions relevant for aquaplaning analysis, often under- or overestimating it compared to measurements. Results indicate that flow resistance is mainly influenced by the Froude number, which is defined using the mean macro-texture depth of the pavement. The study emphasizes that accurate estimation of flow resistance parameters is critical in water film modelling, as it directly affects the reliability of traffic safety assessments. Full article

As exposed bedrocks commonly interface with the soil directly, lacking a transition layer, cracks at rock–soil interface cracks (RSI-Cracks), are well-developed, particularly following wet–dry alternation in karst critical zones. However, inadequate understanding of the influence of RSI-Cracks on multi-path runoff generation around bedrocks has hindered an in-depth comprehension of subsurface-dominated hydrological processes in karst areas. To address this gap, we developed micro-slope models replicating rock–soil interfacial configurations by building upon field investigations. Two conditions, namely, the presence and absence of RSI-Cracks, were incorporated, with rain intensity and rock surface inclination as experimental conditions. Our results indicate that RSI-Cracks significantly alter the runoff output (p < 0.05), exacerbating subsurface water leakage. Compared with that on slopes without RSI-Cracks, the proportion of surface runoff on slopes with RSI-Cracks is reduced, with a reduction range of 4 to 46%. Conversely, RSI-Cracks promote an increase in the proportion of outflow at the rock–soil interface (RSI flow), with an increase range of 7 to 38%. This is an important reason for the aggravation of subsurface water leakage through RSI-Cracks. However, there is no significant change in the water loss caused by internal soil seepage on slopes with or without RSI-Cracks. These findings provide novel insights into underground water loss, with valuable implications for the construction and improvement of hydrological models in karst areas. Full article

The enrichment laws and key controlling factors of coalbed methane (CBM) in the Xishanyao Formation of the Hedong mining area remain unclear, restricting exploration progress. Based on well data and experimental analyses, this study investigates CBM enrichment characteristics and geological controls using genetic identification diagrams. Results demonstrate that CBM exhibits a “high in northwest and low in southeast” planar distribution. Vertically, CBM content is extremely low above 360 m due to weathering oxidation and burnt zone effects, increases within the 360–950 m interval (peaking at 750–950 m), and declines from 950 to 1200 m because of limited gas contribution. Genetic analysis indicates predominantly primary biogenic gas, with a minor component of early thermogenic gas. Enrichment is controlled by structure and hydrogeology: the medium-depth range (358–936 m) on the northern syncline limb and western part of the northern monoclinal zone forms a high-efficiency enrichment zone due to compressive stress from reverse faults and high mineralization groundwater (TDS > 8000 mg/L). While the southern limb, characterized by high-angle tensile fractures and active groundwater runoff, suffers gas loss and generally low gas content (<3.5 m³/t). This study clarifies CBM enrichment laws and enrichment mechanisms, supporting exploration of low-rank CBM in the Hedong mining area. Full article

Gully is the most visible sign of land degradation, but its effects on runoff and sediment dynamics during snowmelt conditions remain poorly understood. This study monitored a typical gully in the Mollisols region of Northeast China to investigate runoff and sediment transport at the Gully Head (GH) and Gully Tail (GT) during spring snowmelt. Results showed that gully significantly influenced snow distribution, with deeper snow accumulation than on slopes. Runoff at the GH lasted 9 days, while gully connectivity extended catchment runoff by 10 additional days. Runoff temporal variation at GH and GT was broadly consistent, with GH contributing 7.4% of the total runoff at GT. Peak runoff discharge and sediment concentration occurred on the sixth day after snowmelt onset, driven by snow cover and air temperature. Gully significantly increased the sediment concentration from the upslope runoff. Runoff responses to temperature varied by melt stage, with GT showing higher sensitivity, especially under high-runoff conditions. High sediment yield was linked not to snow depth, but to late-stage snowmelt and soil thawing, when erosion sensitivity peaked. Hysteresis analysis revealed dominant clockwise loops during this phase, contrasting with figure-eight and counterclockwise patterns in other stages. These findings highlight the importance of targeting erosion control during late snowmelt when runoff intensifies and soils thaw. Full article

Rain-on-snow (ROS) events significantly impact hydrological processes in snowy regions, yet their seasonal drivers remain poorly understood, particularly in low-elevation and low-gradient catchments. This study uses an XGBoost-SHAP explainable artificial intelligence (XAI) model to analyze meteorological and watershed controls on ROS runoff in the Laurentian Great Lakes region. We used daily discharge, precipitation, temperature, and snow depth data from 2000 to 2023, available from HYSETS, to identify ROS runoff. The XGBoost model’s performance for predicting ROS runoff was higher in winter (R² = 0.65, Nash–Sutcliffe = 0.59) than in spring (R² = 0.56, Nash–Sutcliffe = 0.49), indicating greater predictability in colder months. The results reveal that rainfall and temperature dominated ROS runoff generation, jointly explaining more than 60% of total model importance, while snow depth accounted for 8–12% depending on season. Winter runoff is predominantly governed by climatic factors—rainfall, air temperature, and their interactions—with soil permeability and slope orientation playing secondary roles. In contrast, spring runoff shows increased sensitivity to land cover characteristics, particularly agricultural and shrub cover, as vegetation-driven processes become more influential. Snow depth effects shift from predominantly negative in winter, where snow acts as storage, to positive contributions in spring at shallow to moderate depths. ROS runoff responded positively to air temperatures exceeding approximately 2.5 °C in both winter and spring. Land cover influences on ROS runoff differ by vegetation type and season. Agricultural areas consistently increase runoff in both seasons, likely due to limited infiltration, whereas shrub-dominated regions exhibit stronger runoff enhancement in spring. The seasonal shift in dominant controls underscores the importance of accounting for land–climate interactions in predicting ROS runoff under future climate scenarios. These insights are essential for improving flood forecasting, managing water resources, and developing adaptive strategies. Full article

For runoff-generated debris flow continuum mechanics-based early warning models, the computational unit must satisfy the homogeneity assumption of continuum mechanics. Although traditional grid cells meet the homogeneity assumption as computational units, they segment channel geomorphological functional reaches, weaken the clustered mobilization of sediment sources, and constrain efficiency due to grid-by-grid calculations. To address these limitations, we construct a Froude number ($Fr$) calculation model constrained by key factors such as the channel cross-sectional geometry and topographic parameters. The absolute deviation of $Fr$ is used as a criterion for homogeneity within the computational unit. By combining critical shear stress theory and velocity perturbation, physical thresholds for the criteria are derived. A physical model-based method for automatically delineating homogeneous channel units (${CU}_j$) is proposed, ensuring that the geometric features and hydrodynamic parameters within ${CU}_j$ are homogeneous, while ensuring heterogeneity between adjacent ${CU}_j$. Comprehensive multi-scale validation in Yeniu Gully, a typical debris flow catchment in Wenchuan County, demonstrates that parameters such as longitudinal gradient, cross-sectional area, flow depth, and shear stress remain relatively homogeneous within each ${CU}_j$ but differ significantly between adjacent ${CU}_j$. Furthermore, the proposed method can stably characterize key channel geomorphological functional units, such as bends, confluences, abrupt width changes, longitudinal gradient changes, erosion segments, and deposition segments. Sensitivity analysis demonstrates that the method satisfies both robustness and universality under various conditions of rainfall intensity, runoff coefficient, and Manning’s roughness coefficient. Even under the most unfavorable extreme conditions, the accuracy of ${CU}_j$ delineation exceeds 88.64%, indicating high reliability and suitability for deployment in various debris flow catchments. The proposed framework for defining ${CU}_j$ resolves the conflict in traditional computational units between the “continuum model homogeneity requirement” and “geomorphological functional unit continuity,” providing a more rational and efficient computational environment for runoff-generated debris flow continuum mechanics-based early warning models. Full article

SWMM (Stormwater Management Model) is one of the most widely used computation tools in urban water resources management. Traditionally, the choice of rainfall data for calibrating the SWMM model has been arbitrary, lacking clarity on the most suitable rainfall types. In addition, the simplification in the SWMM hydrological module of the rainfall–runoff process, coupled with measurement errors, introduces a high level of uncertainty in the calibration. This study investigates the influences of rainfall types on the highly uncertain SWMM model calibration by implementing the Bayesian inference theory. A Bayesian SWMM calibration framework was established, in which an advanced DREAM(zs) (Differential Evolution Adaptive Metropolis, Version ZS) sampling method was used. The investigation focused on eight key hydrological parameters of SWMM. The impact of rainfall types was analyzed using nine rainfall intensities and three rainfall patterns. Results show that rainfall events equivalent to a one-year return period (R5, 42.70 mm total depth) or higher generally yield the most accurate parameters, with posterior distribution standard deviations reduced by 40–60% compared to low-intensity rainfalls. Notably, three parameters (impervious area percentage [Imperv], storage depth of impervious area [S-imperv], and Manning’s coefficient of impervious area [N-imperv]) demonstrated consistent accuracy irrespective of rainfall intensity, with a coefficient of variation below 0.05 for Imperv and S-imperv across all rainfall intensities. Furthermore, it was found that rainfall events with double peaks resulted in more satisfactory calibration compared to single or triple peaks, reducing the standard deviation of the Width parameter from 168.647 (single-peak) to 110.789 (double-peak). The findings from this study could offer valuable insights for selecting appropriate rainfall events before SWMM model calibration for more accurate predictions when it comes to urban non-point pollution control strategies and watershed management. Full article