Debris Flow Hazard Assessment Research Articles

Hazard Assessment of Debris Flow: A Case Study of the Huiyazi Debris Flow

The Bailong River Basin is situated at the northeastern edge of the Qinghai–Tibet Plateau and the western transition zone of the Loess Plateau, characterized by steep terrain and heavy rainfall. This area experiences frequent occurrences of debris flows, posing serious threats to towns and construction projects. Focusing on the Huaiyazigou debris flow in the Bailong River Basin, numerical simulations of debris flow processes were conducted using Digital Surface Model (DSM) data with a resolution of 5 m × 5 m for various recurrence periods. The simulation results indicate that the debris flow develops rapidly along the gully after formation, decelerating and beginning to deposit upon reaching the cement plant area near the mouth of the gully, eventually merging into the Bailong River. The primary destructive modes of debris flow disasters encompass impact and burial. When encountering buildings, their flow characteristics manifest as deposition and diversion. A debris flow hazard classification model, based on intensity and recurrence periods, was established according to Swiss and Austrian standards, dividing the hazard into low, medium, and high levels. This method generated a debris flow hazard zone map, offering guidance for risk prevention and monitoring. This research demonstrates that using high-precision Digital Surface Models (DSM) can accurately represent the digital information of debris flow gully terrains and buildings. During the simulation process, it realistically reflects the characteristics of the debris flow movement, allowing for the more precise delineation of hazard zones.

Dynamic susceptibility assessment of debris flow hazard after a strong earthquake, Wenchuan County, Sichuan, China

Dynamic susceptibility assessment of debris flow hazard after a strong earthquake, Wenchuan County, Sichuan, China

Seismically induced hillslope disturbance, sediment connectivity and mass wasting: Insights from the 2008 Wenchuan earthquake

A mega-earthquake in a mountainous region can trigger thousands of landslides. Subsequently, these loose co-seismic materials will experience the erosion-transport-sediment process. This process is closely associated with a series of cascading hazards, such as landslides, debris flows and floods. The disturbance and legacy effects of earthquakes have become the focus of attention for post-earthquake reconstruction and disaster mitigation. By combining the modeling of seismic-induced landslide magnitude with an analysis of the coseismic material sediment connectivity and transfer processes, we assessed the impacts of the 2008 Wenchuan earthquake on the mass balance and subsequent geohazard activities. The 2008 Wenchuan earthquake produced 22,785 Mt of deposit storage, 37.9 % of which (∼8636 Mt) is connected to the channels and prone to erosion and transfer by hydrodynamic forces, and the remaining 62.1 % (∼14,149 Mt) was deposited on hillslopes far from the channel network and contributed little to the sediment dynamics. Long-term field observations found a causal relationship between decreasing surface erosion rate and gradual healing of co-seismic deposits due to coarsening by progressive removal of fine grains. We evaluated the residence time of fine-grained (<0.25 mm) landslide materials using the post-earthquake sediment evacuation rate and identified three stages regarding the enhanced erosion and surface mass wasting after the 2008 Wenchuan earthquake, namely, the high activity period (within 40.6 ± 5.4 years), the low activity period (40.6 ± 5.4–107.1 ± 14.2 years), and the steady period (after 107.1 ± 14.2 years). This has important implications for the hazard assessment of landslides and debris flows in understanding and modeling the post-seismic geohazard evolution over multiple timescales.

The application of gray system-variable fuzzy sets coupling theory on the susceptibility assessment of debris flow hazards

The occurrence of debris flow hazards has significant destructive effects people’s safety and the safety of their property, so the risk assessment of debris flow hazards has great significance. The maximum amount of debris flow at one time (X1), the reserves of loose substance (X2), the watershed area (X3), the length of the ditch (X4), the relative height difference (X5), the gradient of side slope (X6), the longitudinal slope of main ditch (X7), the length ratio of replenishment section (X8), the daily maximum rainfall (X9), and Faults developed in the watershed (X10) are selected as the evaluation index at first. Then the gray system-variable fuzzy sets coupling model is introduced; secondly, the relative membership degree matrix about the fuzzy variable sets is established, and the weight coefficients considering the uncertainty of assessment indices are determined based on the entropy weight method; finally, the susceptibility level of debris flow hazards is determined using the mean ranking feature value. The conclusion is drawn that the results obtained based on the coupling technique are consistent with the current specification; its accuracy arrives at 83%, and the method is feasible for the susceptibility level assessment of debris flow hazards. Compared to the traditional variable fuzzy sets model, it avoids the uncertainty of magnitude in the standard analysis, it can ensure the objectivity and accuracy of the calculation result, and its calculation process is simple and efficient. In total, the findings of the proposed model provide an alternate way to assess the susceptibility level of debris flow hazards and improve the evaluation accuracy in the future.

An interpretable framework for the hazard assessment of debris flow based on an improved AHP-EWM method and the SHAP model: a case study of Heishuiwan gully

An interpretable framework for the hazard assessment of debris flow based on an improved AHP-EWM method and the SHAP model: a case study of Heishuiwan gully

Research on Extension Evaluation Method of Mudslide Hazard Based on Analytic Hierarchy Process–Criteria Importance through Intercriteria Correlation Combination Assignment of Game Theory Ideas

Mountain mudslides have emerged as one of the main geological dangers in the Yanshan region of China as a result of excessive rains. In light of this, a multi-step debris flow hazard assessment method combining optimal weights and a topological object metamodel is proposed based on game theory ideas. First of all, based on the geological environment research in Yanshan area, this paper determines the mudslide danger evaluation indexes according to the field investigation and remote sensing image data, then combines them with the theory of topological object element evaluation, utilizes the idea of game theory, and carries out the optimal combination of the weight coefficients derived from hierarchical analysis and the CRITIC method to obtain the final comprehensive weights of the indexes, and forms the combination-assigning topological object element of the mudslide danger topological model. The results suggest that improved weight coefficients can increase topological evaluation precision, which is more in line with objective reality than the traditional method and has some application utility.

The influence of large woody debris on post-wildfire debris flow sediment storage

Abstract. Debris flows transport large quantities of water and granular material, such as sediment and wood, and this mixture can have devastating effects on life and infrastructure. The proportion of large woody debris (LWD) incorporated into debris flows can be enhanced in forested areas recently burned by wildfire because wood recruitment into channels accelerates in burned forests. In this study, using four small watersheds in the Gila National Forest, New Mexico, which burned in the 2020 Tadpole Fire, we explored new approaches to estimate debris flow velocity based on LWD characteristics and the role of LWD in debris flow volume retention. To understand debris flow volume model predictions, we examined two models for debris flow volume estimation: (1) the current volume prediction model used in US Geological Survey debris flow hazard assessments and (2) a regional model developed to predict the sediment yield associated with debris-laden flows. We found that the regional model better matched the magnitude of the observed sediment at the terminal fan, indicating the utility of regionally calibrated parameters for debris flow volume prediction. However, large wood created sediment storage upstream from the terminal fan, and this volume was of the same magnitude as the total debris flow volume stored at the terminal fans. Using field and lidar data we found that sediment retention by LWD is largely controlled by channel reach slope and a ratio of LWD length to channel width between 0.25 and 1. Finally, we demonstrated a method for estimating debris flow velocity based on estimates of the critical velocity required to break wood, which can be used in future field studies to estimate minimum debris flow velocity values.

Hazard assessment of potential debris flow: A case study of Shaling Gully, Lingshou County, Hebei Province, China

The debris flows in the Taihang Mountain region in North China are basically triggered by rainstorms. Firstly, the debris flow susceptibility of the Shaling Gully, Lingshou County, Hebei Province, China was analyzed in this paper to evaluate its hazard and effect on the downstream proposed structures. Secondly, the maximum flow depth and velocity of the potential debris flow in Shaling Gully were numerically simulated based on the FLO-2D model, and the simulation results indicate that the flow depths under the 50-year and 100-year rainstorms will have some effect on the downstream proposed structures. With debris flow intensity classification, the hazard of potential debris flow in Shaling Gully was classified. According to the flow depths and velocities simulated by FLO-2D model, the ARCGIS10.8 software was adopted to optimize the hazard zones, and therefore the hazard zonation map was established. With consideration of simulation results under natural conditions and other factors such as gully feature, a 4 m high and 40 m wide retaining dam was designed. The numerical simulation results show that the retaining dam may decrease the debris flow hazard to a negligible level, which offers some beneficial reference to the subsequent engineering design for Shaling Gully.

Characteristics, Dynamic Analyses and Hazard Assessment of Debris Flows in Niumiangou Valley of Wenchuan County

Niumiangou valley, the epicenter of the 12 May 2008 Wenchuan earthquake (MS 8.0), became an area with frequent and dense debris flow disasters post-earthquake. Based on the in situ investigations after the earthquake on 14 August 2010 and a series of gathered data, characteristics and dynamic analyses of post-earthquake debris flows in Niumiangou valley were conducted, and then their hazard degree was assessed. Some research conclusions are obtained: (1) these post-earthquake debris flows have some typical characteristics, such as rainstorm viscous-type debris flow, happening usually between 11 p.m. and 5 a.m., broken out in the main channel as well as six branch gullies at the same time and also induced in the branches with good vegetation; (2) the dynamic parameters of Niumiangou debris flow (including volumetric weight, velocity, peak discharge, impact force, total amount of debris flow, total amount of solid materials washed out by single debris flow, maximum height of the debris flow rises and super elevation in bend) are relatively significant, and due to which it can be indicated that these debris flow disasters have great destructive power and harmfulness; (3) the hazard degree of debris flow in Niumiangou valley is very high, compared with the debris flows that occurred in the years of 2008 and 2013 in Niumiangou valley post-Wenchuan earthquake, and the comparison result shows that the hazard degree of debris flow in Niumiangou valley is relatively higher, which is consistent with the current situation. Therefore, according to these results, debris flows in Niumiangou valley are in the development phase and large-scale rainfall-induced debris flow disasters, with greater damage and stronger wallop, will easily occur in the rainy seasons of the 20 years after the earthquake.

Advancing debris flow hazard and risk assessments using debris flow modeling and radar derived rainfall intensity data

Debris flow hazard and risk assessments are critical tools in mitigating and planning for these events. Existing debris flow hazard assessments can provide a rapid view of the likelihood of debris flows in recently burned watersheds and along stream segments within the watershed. Furthermore, debris flow volumes can be predicted for these watersheds and along the stream segments. Advances in modeling and remote-sensing data can add further value to the rapid assessments. Here, modeled debris flow volumes and a more detailed understanding of rainfall conditions highlight a need to reconcile debris flow probabilities and volumes using local conditions. Modeled debris flow volumes are consistently lower than even the lowest predicted volumes from empirical models used in the debris flow hazard assessments. Watershed probability and volume relations also over predict based on our probabilities derived from rainfall intensity from Multi-Radar/Multi-Sensor System 1-hr data. Probability and volume measures need to be further considered as the conservative measures of the rapid assessments have implication for risk analyses required for planning and management decisions, and ultimately for design and cost of mitigation to manage risk.

Debris flow hazard assessment: Laboratory experiences and numerical modelling

In the last years, the study of debris flow has become very important in the research activity and in the engineering practice. The use of numerical models is able for the study of debris flow’s propagation. The study area is located in the north-east Sicilian coast and in particular in the municipality of Gioiosa Marea, severely affected by landslides occurred from 2000 to 2013. In this case study, the FLO-2D code has been used. The soil parameters has been determined by means of in situ investigations and laboratory tests. The knowledge of the physical and mechanical properties is very important to define the input parameters of the model, including the volumetric concentration associated with the soil friction angle.

Simulating two-phase debris flows in HEC-RAS at Hummingbird Creek, British Columbia, Canada

Debris flows are typically modelled as a single homogeneous surge due to lack of data to support more complex model development and due to lack of time and funding for the practitioner and the communities they aim to support. Coarse debris flows are typically characterized by a coarse front, followed by a muddy slurry, that is then followed by a hyperconcentrated flow phase with lesser sediment concentrations. Presented herein is the modelling for a debris flow hazard assessment for Hummingbird Creek, British Columbia, Canada. Model calibration best matched the observed debris flow deposit when the coarse front and hyperconcentrated flow were modelled separately in two phases allowing for separate flow rheologies to be used for the front and the tail of the debris flow, and allowing for deposition between phases. Further research is needed to understand when simulation of two-phase flow may be most representative, particularly when no calibration data is available.

Predicting burn severity for integration with post-fire debris-flow hazard assessment: a case study from the Upper Colorado River Basin, USA

Background Burn severity significantly increases the likelihood and volume of post-wildfire debris flows. Pre-fire severity predictions can expedite mitigation efforts because precipitation contributing to these hazards often occurs shortly after wildfires, leaving little time for post-fire planning and management. Aim The aim of this study was to predict burn severity using pre-fire conditions of individual wildfire events and estimate potential post-fire debris flow to unburned areas. Methods We used random forests to model dNBR from pre-fire weather, fuels, topography, and remotely sensed data. We validated our model predictions against post-fire observations and potential post-fire debris-flow hazard estimates. Key results Fuels, pre-fire weather, and topography were important predictors of burn severity, although predictor importance varied between fires. Post-fire debris-flow hazard rankings from predicted burn severity (pre-fire) were similar to hazard assessments based on observed burn severity (post-fire). Conclusion Predicted burn severity can serve as an input to post-fire debris-flow models before wildfires occur, antecedent to standard post-fire burn severity products. Assessing a larger set of fires under disparate conditions and landscapes will be needed to refine predictive models. Implications Burn severity models based on pre-fire conditions enable the prediction of fire effects and identification of potential hazards to prioritise response and mitigation.

A multi-step hazard assessment for debris-flow prone areas influenced by hydroclimatic events

Hazard assessment studies are fundamental to identifying disaster-prone areas, especially in locations with high environmental and socioeconomic vulnerability. This study proposes a multi-step debris-flow hazard assessment, based on the combination of Logistic Regression (LR) analysis, numerical simulation and rainfall back-analysis. A landslide-prone area of 84 km2 is chosen as test-site, including 20 river catchments and one of the largest petrochemical plants in Latin America. Rainfall is the main influencing factor in debris-flow initiation, as highlighted by the LR analysis, followed by soil cover and slope. The analysis also indicated the catchments more susceptible to debris flows and the simulation results show that the average runout distance in these catchments is 470 m, with an average peak flow height of 5 m and a peak velocity of 23 m s−1. Debris flows are triggered by short duration (<48 h), high-intensity (>200 mm) precipitation, with return periods that vary from 3 to 10 years. Five levels of hazard (very low to very high) are, then, proposed for the study site, based mainly on 48-h accumulated rainfall and flow properties. Industrial and residential areas in the projected debris-flow route generally exhibit the highest overall hazard levels, as many were developed in the depositional area of debris flows and near fluvial courses, where associated floods and flash floods may occur. As pointed out by recent studies, an increase in the frequency of extreme precipitation events is projected in the Serra do Mar region and when the general short return period of the debris-flow triggering rainfall is considered (<10 years), large magnitude (>105 m3) debris flows are likely to occur in the near future.

Debris Flow Hazard Assessment in District Chitral, Eastern Hindu Kush, Pakistan

The aim of this study is debris flow risk zonation using geological and hydrometeorological indicators in district Chitral, Hindu Kush Region Northwest Pakistan. The research is based on secondary data. Multi criteria Analysis (MCA) in Geographical Information System (GIS) environment was used to achieve the objective of the study. The geological and hydrometeorological parameters were analyzed by making five classes of each parameter. The classes are ranked as most favorable and least favorable with numerical weights. The weights were assigned in accordance to their importance in debris flow occurrence. Then weighted overlay analysis techniques were applied to develop composite map representing the importance of each factor. Debris flow risk zonation map was resulted into four classes very high risk zones, high risk zone, moderate zone, low risk zone. The geology of the study area is diverse with frequents earthquakes. Similarly the forest cover is decreasing due to anthropogenic activities. The area is also characterized by long cold winters with frost action. These factors are destabilizing the slope. During summer season rain storm event results high surface runoff and peak discharge in the perennial and non-perennial channels which results flood and debris flow. These events result human life loss and disruption. The main villages located in very high risk zone are Mulkoh, Mastuj, Reshun, Shegram, Terich Gol, Rogar, Asurat, Boni, Brep and Rech Tockhow. They have been frequently affected by hazard in the past decade. Out of the total area, very high risk zone is expanded over 8%, high risk zone is expanded over16%, moderate risk zone is 29% and the rest is low risk zone. This study has highlighted the risk zones which will help disaster management authorities and policy makers to reduce the risk of debris flow in future.

Debris Flow Hazard Assessment in District Chitral, Eastern Hindu Kush, Pakistan

Debris Flow Hazard Assessment in District Chitral, Eastern Hindu Kush, Pakistan

A Scalable Framework for Post Fire Debris Flow Hazard Assessment Using Satellite Precipitation Data

AbstractWildfire is a global phenomenon that has dramatic effects on erosion and flood potential. On steep slopes, burned areas are more likely to experience significant overland flow during heavy rainfall leading to post fire debris flows (PFDFs). Previous work establishes methods for PFDF hazard assessment, often relying on regional‐scale parameterizations with in‐situ rainfall measurements to categorize hazard as a function of meteorological and surface properties. We present a globally scalable approach to extend the benefit these models provide to new areas. Our new model relies on publicly available satellite‐based inputs with a global extent to provide first order hazard assessments of recently burned areas. Our results show it is possible to identify the conditions relevant for PFDF‐initiation processes across a variety of physiographic settings. Improvements to satellite‐borne rainfall intensity data and increased availability of PFDF occurrence data worldwide are expected to enhance model skill and applicability further.

Risk Assessment of Debris Flow in a Mountain-Basin Area, Western China

Debris flow risk comprehensively reflects the natural and social properties of debris flow disasters and is composed of the risk of the disaster-causing body and the vulnerability of the carrier. The Bailong River Basin (BRB) is a typical mountainous environment where regional debris flow disasters occur frequently, seriously threatening the lives of residents, infrastructure, and regional ecological security. However, there are few studies on the risk assessment of mountainous debris flow disasters in the BRB. By considering a complete catchment, based on remote sensing and GIS methods, we selected 17 influencing factors, such as area, average slope, lithology, NPP, average annual precipitation, landslide density, river density, fault density, etc. and applied a machine learning algorithm to establish a hazard assessment model. The analysis shows that the Extra Trees model is the most effective for debris flow hazard assessments, with an accuracy rate of 88%. Based on socio-economic data and debris flow disaster survey data, we established a vulnerability assessment model by applying the Contributing Weight Superposition method. We used the product of debris flow hazard and vulnerability to construct a debris flow risk assessment model. The catchments at a very high-risk were distributed mainly in the urban area of Wudu District and the northern part of Tanchang County, that is, areas with relatively dense economic activities and a high disaster frequency. These findings indicate that the assessment results provide scientific support for planning measures to prevent or reduce debris flow hazards. The proposed assessment methods can also be used to provide relevant guidance for a regional risk assessment of debris flows in the BRB and other regions.

Physical process-based runout modeling and hazard assessment of catastrophic debris flow using SPH incorporated with ArcGIS: A case study of the Hongchun gully

Catastrophic debris flows frequently occur in mountainous areas after an earthquake owing to a substantially increased amount of loosened co-seismic material. Debris flows pose a serious challenge for the reconstruction of earthquake-stricken areas because of their potential reoccurrence over the course of several years after a given earthquake event. It is therefore essential to clarify the dynamics of large-scale debris flows and accurately assess the potential hazard risks. This study selected the Hongchun gully debris flow that occurred on August 14, 2010 in the areas affected by the Wenchuan earthquake in southwestern China as a typical case to analyze the formation conditions and physical processes of catastrophic debris flows. The smoothed particle hydrodynamics (SPH) method was used to reconstruct the physical process of the Hongchun gully debris flow across 3D terrain. The SPH numerical results were integrated into the ArcGIS platform to perform further spatial analysis of the hazard intensity and identify the hazard risk level. The calculated accumulated hazard area agrees well with the field data. By introducing a frequency-magnitude empirical formula, a hazard assessment model of debris flows is proposed based on flow depth and momentum, and applied to predict the potential risk of the Hongchun gully debris flow under different recurrence periods. This work provides a new method for performing hazard assessments of debris flows, and also serves as a guide for reconstruction planning in earthquake-hit areas.

Hazard Assessment of Debris Flow Based on Infinite Irrelevance Method and Probabilistic Neural Network Coupling Model

Debris flow is one of the most harmful natural disasters, which seriously damages the ecological environment balance, human life safety and property loss. Therefore, it is necessary to predict and assess the hazard of debris flow. This paper proposes an effective model for predicting the hazard of debris flow, which is a coupled model based on the Infinite Irrelevance Method (IIM) and the Probabilistic Neural Network (PNN). Taking Xiuyan Manchu Autonomous County, Liaoning Province, China as an example, this paper selects 31 key debris flow trenches according to the geological data survey and the characteristics of debris flow disasters, and uses IIM to screen the frequency, watershed area, height difference, debris reserves, rainfall, lithology, slope, population density, NDVI, a total of 9 influencing factors as the sample data set of PNN, and randomly divided into a training set and test set, the ratio is 65% and 35%. Compared with the IIM-GRNN model, the evaluation results show that the accuracy rate of the IIM-PNN model is 91%, which is more excellent than the IIM-GRNN model with an accuracy rate of 82%. The IIM-PNN model can more effectively classify and predict the hazard of debris flow, and can be used in other regions with similar geological environmental characteristics to take measures to manage and prevent the recurrence of the disaster.