Among natural disasters,flash floods are the most destructive events,causing signif-icant damage to the economy and posing a serious threat to human life and property.Comprehensive risk assessment of these sudden floo...Among natural disasters,flash floods are the most destructive events,causing signif-icant damage to the economy and posing a serious threat to human life and property.Comprehensive risk assessment of these sudden floods is a key strategy to mitigate their impact.Accurate analysis of flash flood hazards can greatly enhance prevention efforts and inform critical decision-making processes,ultimately improving our ability to protect communities from these fast-onset disasters.This study analyzed the driving forces of flash flood disaster-causing factors in Heilongjiang Province.Meanwhile,nine different categories of variables affecting the occurrence of flash floods were selected,and the degree of influence of each driving factor on flash floods was quantitatively analyzed,and the driving force analysis of the driving factors of flash floods in Hei-longjiang Province was carried out by using the geographic probe model.This paper employs an uncertainty approach,utilizing a statistical-based interval weight deter-mination technique for evaluation indices and a two-dimensional information-based interval number sorting method.These methodologies are combined to construct a comprehensive flash flood risk assessment model.On this basis,the model was implemented in six regions within China's Heilongjiang province to evaluate and prioritize flash flood risks.The resulting risk ranking for these areas was as follows:Bayan≻Shuangcheng≻Boli≻Suibin≻Hailun≻Yian.The findings demonstrate that the interval number-based evaluation method effectively handles uncertainty,providing a more reliable risk grading system.This approach,by leveraging modern scientific advances and risk quantification techniques,is crucial for improving disaster management and mitigating flash flood impacts.展开更多
Rainstorm-induced flood hazards in mountainous areas often result in complex cascading effects by interacting with environmental and human systems.However,traditional studies typically categorize them simply as clearw...Rainstorm-induced flood hazards in mountainous areas often result in complex cascading effects by interacting with environmental and human systems.However,traditional studies typically categorize them simply as clearwater floods or debris floods/flows,overlooking their evolutionary characteristics and compound impacts.This study presents a novel classification-based approach to investigate the formation and destructive mechanisms of a catastrophic composite disaster of flash flood and debris flow in the Dayao Gully(DYG)catchment in Hanyuan County,Sichuan Province,China.The event resulted in 14 fatalities,25 missing persons,and extensive infrastructure damage.Through comprehensive field investigations and multi-method analysis,three distinct disaster zones were identified with different magnitudes and impacts:(1)a clearwater flood disaster region with minimal geomorphological changes under a 5-year return period rainfall;(2)a debris flood disaster region triggered by a 30-year return period rainfall,leading to intense sediment transport with a total deposit volume of 52,511 m^(3);and(3)a sediment-induced flood disaster region characterized by significant riverbed aggradation and infrastructure destruction due to sediment-induced blockage effects.The results reveal that the cascading characteristics of this composite disaster were primarily driven by intense rainfall,enhanced sediment transport motivated by supracritical shear stress,and interactions with human infrastructure(e.g.,bridges and buildings).This classification-based approach provides a quantitative assessment of spatial characteristics of cascading flood disasters,offering new insights into their evolutionary characteristics and highlighting the necessity for targeted disaster mitigation strategies in sedimentprone mountainous regions.展开更多
The Hengduan Mountains region(HMR)is one of the most densely distributed and severe flash flood disaster-prone areas in southwest China.It is also a key area for major engineering projects and beautiful countryside co...The Hengduan Mountains region(HMR)is one of the most densely distributed and severe flash flood disaster-prone areas in southwest China.It is also a key area for major engineering projects and beautiful countryside construction in Southwest China.However,previous studies have not systematically summarized the development characteristics and formation modes of flash flood disasters in the HMR,which limits the development of theoretical and technical system for flood control.In this study,we focused on the physical processes of flash flood disasters in the HMR,including generation,movement,and disaster formation,and clarified the dominant disaster-inducing conditions(multiple humid monsoon circulation,high potential energy and high heterogenous underlying surface)and disaster development characteristics(high spatio-temporal heterogeneity,highly concentrated energy,chain and cascading effects,and clustered occurrence)of flash floods in the HMR.Based on the entire processes of flash flood disasters,three major formation modes have been summarized:the runoff generation mode of vegetation-hydrology-soil coupling dominated by high hydraulic gradient in mountainous areas,strong flow-sediment coupling movement,and serious disaster losses due to high exposure of disaster bearing objects.Finally,based on the issues in previous research,four future research challenges for flash flood disaster in the HMR were proposed.Our study provides insights into disaster prevention and reduction research,including fundamental theoretical system,precise risk assessment of regional disasters,and accurate early warning and forecasting of flash floods.展开更多
Flash flood is one of the major meteorological disasters on the Tibet Plateau(TP).Flash flood risk regionalization based on the theory of flash flood occurrence risk is the essential basis for relative risk management...Flash flood is one of the major meteorological disasters on the Tibet Plateau(TP).Flash flood risk regionalization based on the theory of flash flood occurrence risk is the essential basis for relative risk management.The flash flood risk regionalization and the high-resolution grid mountain flood risk level in TP is carried out by using ArcGIS with the indicators of rainfall,days of heavy rain,vegetation cover,slope,relative elevation difference,river network density,population density,average GDP and traffic density.The areas with high mountain flood risk are mainly located in the middle and downstream of Yarlung,the Nujiang River Valley,the Jinsha River and Lancang River Basin.Besides,the results of flash flood disaster risk regionalization were tested by using historical flash flood disaster data and calamity census data.The disasters occurred in high-risk and sub-high-risk regions are accounted for 73%.Flash floods that cause casualties and economic losses of more than 100,000 CNY(Chinese Yuan)occurred in high-risk areas.Flash flood risk assessment may provide reference for the prevention and control of geological disasters in TP,improve disaster prevention and mitigation capabilities,reduce the hazards of flash floods to social development.展开更多
In a globally warming world, subtropical regions are generally expected to become drier while the tropics and mid-high latitudes become wetter. In line with this, Southwest China, close to 25°N, is expected to be...In a globally warming world, subtropical regions are generally expected to become drier while the tropics and mid-high latitudes become wetter. In line with this, Southwest China, close to 25°N, is expected to become increasingly prone to drought if annual mean precipitation decreases. However, despite this trend, changes in the temporal distribution of moisture supply might actually result in increased extreme rainfall in the region, whose climate is characterized by distinct dry and wet seasons. Using hourly and daily gauge observations, rainfall intensity changes since 1971 are exalnined for a network of 142 locations in the region. From the analysis, dry season changes are negligible but wet season changes exhibit a significantly strong downward trend [-2.4% （10 yr）^-1], particularly during the past 15 years [-17.7% （10 yr）^-1]. However, the intensity of events during the wettest of 5% hours appears to steadily increase during the whole period [1.4% （10 yr）^-1], tying in with government statistical reports of recent droughts and flooding. If the opposing trends are a consequence of a warming climate, it is reasonable to expect the contradictory trend to continue with an enhanced risk of flash flooding in coming decades in the region concerned.展开更多
Flash floods are responsible for loss of life and considerable property damage in many countries.Flood susceptibility maps contribute to flood risk reduction in areas that are prone to this hazard if appropriately use...Flash floods are responsible for loss of life and considerable property damage in many countries.Flood susceptibility maps contribute to flood risk reduction in areas that are prone to this hazard if appropriately used by landuse planners and emergency managers.The main objective of this study is to prepare an accurate flood susceptibility map for the Haraz watershed in Iran using a novel modeling approach(DBPGA)based on Deep Belief Network(DBN)with Back Propagation(BP)algorithm optimized by the Genetic Algorithm(GA).For this task,a database comprising ten conditioning factors and 194 flood locations was created using the One-R Attribute Evaluation(ORAE)technique.Various well-known machine learning and optimization algorithms were used as benchmarks to compare the prediction accuracy of the proposed model.Statistical metrics include sensitivity,specificity accuracy,root mean square error(RMSE),and area under the receiver operatic characteristic curve(AUC)were used to assess the validity of the proposed model.The result shows that the proposed model has the highest goodness-of-fit(AUC=0.989)and prediction accuracy(AUC=0.985),and based on the validation dataset it outperforms benchmark models including LR(0.885),LMT(0.934),BLR(0.936),ADT(0.976),NBT(0.974),REPTree(0.811),ANFIS-BAT(0.944),ANFIS-CA(0.921),ANFIS-IWO(0.939),ANFIS-ICA(0.947),and ANFIS-FA(0.917).We conclude that the DBPGA model is an excellent alternative tool for predicting flash flood susceptibility for other regions prone to flash floods.展开更多
In recent years, flash flood disasters have occurred frequently in southwest China due to the increased frequency of extreme climate events. To solve this problem, great efforts have been made in studying the process ...In recent years, flash flood disasters have occurred frequently in southwest China due to the increased frequency of extreme climate events. To solve this problem, great efforts have been made in studying the process of flash flood. However, little attention was paid on bearing body of hazard, the clusters of buildings. Thus the real disaster mechanism of flash flood remains unclear.Accordingly, based on the experiments of artificial flash floods in a conceptual solid model, this paper focuses on the flood-impacted inundation characteristics of the building clusters at different locations of the gully model, in order to obtain a better understanding of the disaster process and the interaction between the flash floods and building clusters. The results showed that, in a typical smallscale flash flood gully with hot and dry climate, 1)clusters of buildings on an alluvial fan could reduce about 35% of the flooding area by blocking the diffusion of the flood to the depression areas, and could also promote the deposition in lower reaches of the river channel by blocking the overbank flow from going back into the channel, making the width-depth ratio of the channel larger. 2) The flash flood rates of disaster and hazard on the alluvial fan are generally higher than that of the inner gully. For the inner gully,buildings located on the beaches along the lower river and the transitional areas of the straight channel and channel bends can easily be affected because of their lower elevations. For the alluvial fan, buildings nearby the meanders suffer the greatest impacts because of bank collapsing and flooding. 3) The safe vertical distance from a building to the river channel is 13 m for the buildings in the inner gully under extreme floods. Below this threshold, the smaller the vertical distance is, the greater the risk exposure is. For the buildings on the alluvial fan, especially for the buildings near the concave bank of the top rush point,the horizontal distance is more important, and the safe value is 80 m under extreme floods.展开更多
Flash flood hazard mapping is a supporting component of non-structural measures for flash flood prevention. Pilot case studies are necessary to develop more practicable methods for the technical support systems of fla...Flash flood hazard mapping is a supporting component of non-structural measures for flash flood prevention. Pilot case studies are necessary to develop more practicable methods for the technical support systems of flash flood hazard mapping. In this study, the headwater catchment of the Xiapu River Basin in central China was selected as a pilot study area for flash flood hazard mapping. A conceptual distributed hydrological model was developed for flood calculation based on the framework of the Xinanjiang model, which is widely used in humid and semi-humid regions in China. The developed model employs the geomorphological unit hydrograph method, which is extremely valuable when simulating the overland flow process in ungauged catchments, as compared with the original Xinanjiang model. The model was tested in the pilot study area, and the results agree with the measured data on the whole. After calibration and validation, the model is shown to be a useful tool for flash flood calculation. A practicable method for flash flood hazard mapping using the calculated peak discharge and digital elevation model data was presented, and three levels of flood hazards were classified. The resulting flash flood hazard maps indicate that the method successfully predicts the spatial distribution of flash flood hazards, and it can meet the current requirements in China.展开更多
Flash floods are one of the most dangerous natural disasters,especially in hilly terrain,causing loss of life,property,and infrastructures and sudden disruption of traffic.These types of floods are mostly associated w...Flash floods are one of the most dangerous natural disasters,especially in hilly terrain,causing loss of life,property,and infrastructures and sudden disruption of traffic.These types of floods are mostly associated with landslides and erosion of roads within a short time.Most of Vietnamis hilly and mountainous;thus,the problem due to flash flood is severe and requires systematic studies to correctly identify flood susceptible areas for proper landuse planning and traffic management.In this study,three Machine Learning(ML)methods namely Deep Learning Neural Network(DL),Correlation-based FeatureWeighted Naive Bayes(CFWNB),and Adaboost(AB-CFWNB)were used for the development of flash flood susceptibility maps for hilly road section(115 km length)of National Highway(NH)-6 inHoa Binh province,Vietnam.In the proposedmodels,88 past flash flood events were used together with 14 flash floods affecting topographical and geo-environmental factors.The performance of themodels was evaluated using standard statisticalmeasures including Receiver Operating Characteristic(ROC)Curve,Area Under Curve(AUC)and Root Mean Square Error(RMSE).The results revealed that all the models performed well(AUC>0.80)in predicting flash flood susceptibility zones,but the performance of the DL model is the best(AUC:0.972,RMSE:0.352).Therefore,the DL model can be applied to develop an accurate flash flood susceptibility map of hilly terrain which can be used for proper planning and designing of the highways and other infrastructure facilities besides landuse management of the area.展开更多
In China,flash floods are one of the main natural disasters causing loss of life and damage to infrastructure.The threat of flash floods is exacerbated with climate change and increased human activities,such that the ...In China,flash floods are one of the main natural disasters causing loss of life and damage to infrastructure.The threat of flash floods is exacerbated with climate change and increased human activities,such that the number of disasters has shown a clear upward trend in recent years.However,due to the scarcity of instrumental data or overly short timeseries,we are still lacking critical data to understand spatio-temporal patterns and driving factors of extreme flash floods.This missing knowledge is however crucial for a proper management of these hazards,especially in remote mountain environments.In forested catchments,dendrogeomorphology allows the reconstruction of past process activity based on growth disturbances(GDs)in trees that have been affected by past flash floods.Therefore,in our study,for the first time,we reconstruct past flash floods in the Qilian Mountains,northeast Tibetan Plateau,over past centuries.To this end,we sampled 99 Qinghai spruce(Picea crassifolia)trees affected by flash floods,with a total of 194increment cores,and identified 302 GDs induced by past flash floods.These GDs have been caused by at least 21 flash floods that we are able to reconstruct over the last 170 years.The position of GDs within tree rings and the intra-seasonal dating of past events also allowed discussion of the likely synoptic situations that may have led to the triggering of flash floods in the past.Logistic regression analysis confirms that significant correlation exists between cumulative maximum 5-day August-September precipitation and reconstructed flash floods,which is corresponding to the majority of scars and related tangential rows of traumatic resin ducts(TRDs)found in the latewood portion of growth rings.These results support the idea that abundant precipitation occurring at the end of the summer season and early fall is the key factor driving flash floods in our study area.Our research not only fills the gaps regarding historical flash flood histories in the Qilian Mountains,but also provides a scientific basis for the region's response to climate change and flood prevention and reduction.展开更多
Flash floods result from a complex interaction among hydro-meteorological, hydrological, and hydraulic processes across various spatial and temporal scales. Sichuan Province suffers flash floods frequently owing to mo...Flash floods result from a complex interaction among hydro-meteorological, hydrological, and hydraulic processes across various spatial and temporal scales. Sichuan Province suffers flash floods frequently owing to mountain weather and topography. A flash flood and gravel bed load transport are two key relative problems in mountain river engineering. Bed materials are often encountered in alternate scouring and deposition in mountain fluvial processes during a flash flood. In this circumstance, CRS-1 bed load numerical model jointly with scale physical model is employed to predict water level and gravel bed scour and deposition for design of flood control dykes and flash flood disaster mitigation. A case study on the mechanism of a flash flood disaster induced by bed load transport for a hydropower station in Sichuan Province is conducted. Finally, suggestions to protect the hydropower station are proposed.展开更多
Damage to rural buildings in mountainous regions caused by flash floods accounts for a significant proportion of economic losses from disasters.The unreinforced masonry(URM)wall is the most vulnerable structural eleme...Damage to rural buildings in mountainous regions caused by flash floods accounts for a significant proportion of economic losses from disasters.The unreinforced masonry(URM)wall is the most vulnerable structural element of rural buildings exposed to flash floods.The failure of a URM wall indicates damage to rural buildings in flash floods.Based on the yield line theory of out-of-plane damage of URM walls and the virtual work method,brittle failure criteria for URM walls under the impact of flash floods were established.According to the field investigation data of the 26 June 2020 flash flood event in Damawu Gully and the corresponding simulation results of FLO-2D,the disaster-causing process was analysed,and the failure criteria were validated.Three building parameters were identified to influence the flood-resistance of URM walls,including the mortar grade,the span-to-height ratio of the wall,and the number of floors of the rural building.The results showed that the cause of the 26June disaster was the diversion of a 50-year flash flood into the residential community on the alluvial fan.The affected buildings were constructed with hollow blocks and lacked flood-resistance reinforcement.The critical failure depth of a URM wall restrained at the top by ring beams(RBs)under hydrostatic load conditions is 1.17 to 1.20 times greater than that of a URM wall without RBs,and the difference is even more pronounced when lowerstrength mortar is used.The flood-resistance of a URM wall constructed with Mb 7.5 mortar and restrained by RBs is almost as strong as that of a URM wall constructed with Mb 20 mortar and without RBs.The span-to-height ratio of a URM wall should not be greater than 1.875 in this case.However,the flood-resistance of a URM wall with RB restraint is almost independent of the span-to-height ratio.The brittle fracture energy of masonry mortar is more crucial to the flood-resistance of 4-edge restrained URM walls if L/Z>1.875.The flood-resistance of the URM wall of the first storey increases linearly with the number of floors.Single-storey rural buildings should be given priority to the use of high-grade masonry mortar and high-density blocks to improve flood-resistance.The failure criteria and the influence laws of building parameters on the flood-resistance of URM walls can provide references for flash flood mitigation and flood-resistance reinforcement of rural buildings in mountainous regions of Southwest China.展开更多
In the context of climate change and human activities,flood disasters in arid mountainous areas have become increasingly frequent,and seriously threatened the safety of people's lives and property.Rapid and accura...In the context of climate change and human activities,flood disasters in arid mountainous areas have become increasingly frequent,and seriously threatened the safety of people's lives and property.Rapid and accurate flash flood inundation modelling is an essential foundational research area,which can aid in the reduction of casualties and the minimization of disaster losses;however,this modelling is also very difficult,and models need to be urgently developed to address flash flood forecasting and warnings.The objective of this study is to construct a numerical modelling method for flash floods in drylands.Based on a 2D high-resolution flood numerical model(Flood Map-Hydro Inundation2D),we hindcasted the dynamic process of flash flooding and show the spatio-temporal characteristics of flash flood inundation for the“8·18”flash flood disaster that occurred in Datong county,Qinghai province.The results showed that the model output effectively agreed with the observed inundation after the event in terms of both spatial extent and temporal process.Extensive flooding mainly occurred between 00:00 and 01:00 on August 18,2022.Qingshan,Hejiazhuang and Longwo villages were affected most heavily.We further conducted model sensitivity analysis and found that the model was highly sensitive to both roughness and hydraulic conductivity in drylands,and the effect of hydraulic conductivity was more pronounced.Our study confirmed the good performance of our model for the simulation of flash flooding in arid areas and provides a potential method for flash flood assessment and management in arid areas.展开更多
Water depths and flow velocities decisively influence the damage caused by flash floods.Geographic Information System(GIS)is a powerful and useful tool,allowing the spatial analysis of results obtained by hydraulic mo...Water depths and flow velocities decisively influence the damage caused by flash floods.Geographic Information System(GIS)is a powerful and useful tool,allowing the spatial analysis of results obtained by hydraulic modelling,namely from the HEC-RAS/HEC-GeoRAS software.The GIS spatial analysis performed in this study seeks to explain and quantify the spatial relationships between the stream channel features and flow components during flash flood events.Despite these relationships are generically known,there are few studies exploring this subject in different geographic contexts.A 1D hydraulic model was applied in a small watershed in Portugal,providing good results in the definition of floodable areas,water depths and longitudinal velocities.No direct relationship was found between water depths and velocities in the floodable areas;however,negative strong correlations were found between the two flow components along the stream centerlines.Bed slope,channel and flood width,and roughness prove to be highly relevant on the longitudinal variations of water depths and velocities and on the location of maximum values.Increasing peak discharges and return periods(R;)can change the relationships between water depths and velocities at the same location.Results can be improved with more accurate elevation data for stream channels and floodplains.展开更多
Morphometric analysis and flash floods assessment were conducted for the watersheds of Ras En Naqb escarpment, south Jordan. The study area comprises of twelve small watersheds occupying the faulted-erosional slopes, ...Morphometric analysis and flash floods assessment were conducted for the watersheds of Ras En Naqb escarpment, south Jordan. The study area comprises of twelve small watersheds occupying the faulted-erosional slopes, and the dip slopes. The drainage network shows that dendritic and sub-dendritic patterns dominated the dip slopes, whereas trellis pattern characterized the faulted-erosional slopes. Stream orders range from fourth to sixth order. The mean bifurcation ratios vary between 4.2 and 5.38 for the dip slope basins, and between 3.5 and 5.0 for the faulted-erosional slope watersheds, indicating a noticeable influence of structural disturbances (i.e., faulting and uplifting), and rejuvenation of drainage networks. All watersheds have short basin lengths, ranging from 23.8 km to 42.2 km for the dip slope basins, and between 15.3 km and 45.4 km for the faulted-erosional slope catchments. This is indicative of high flooding susceptibility associated with heavy rainstorms of short duration. The circularity ratios range from 0.177 to 0.704 which denote that the catchments are moderately circular on the faulted-erosional slopes, and to some extent elongated on the dip slopes. The length of overland flow values ranges from 0.854 to 0.924 for the dip slope catchments, whereas L<sub>O</sub> values for the faulted-erosional slopes vary from 0.793 to 0.945 denoting steep slopes and shorter paths on both dip slope and faulted-erosional slope watersheds. Values of stream frequency range from 1.509 to 1.692 for the dip slope, and from 1.688 to 2.0 for the faulted-erosional slope catchments. F<sub>S</sub> values are also indicative of slope steepness, low infiltration rate, and high flooding potential. The watersheds of the dip slopes show lower values of form factor varying from 0.079 to 0.364, indicating elongated shape and suggesting a relatively flat hydrograph peak for longer duration. Similarly, values of D<sub>d</sub> are high for catchments on the dip slope basins (1.709 - 1.85) and the faulted-erosional slope watersheds (1.587 - 2.0) indicating highly dissected topography, high surface runoff, low infiltration rate, and consequently high flooding potential. Furthermore, high relief values exist, ranging from 388 m to 714 m for the dip slope basins, and from 421 m to 846 m for the faulted-erosional slope catchments indicting high relief and steep slopes. Morphometric analysis, and flash flood assessment suggest that ten watersheds (83.3%) are categorized under high and intermediate flooding susceptibility, and the faulted-erosional slope catchments are more hazardous in terms of flooding. Thus the protection of Ma’an, El Jafr rural Bedouin settlements, and Amman-Aqaba highway from recurrent flooding is essential to ensure sustainable future development in Ras En Naqb-Ma’an area.展开更多
The Safaga Region(SR)is part of the Red Sea mountain range in Egypt.Catastrophic flash flooding is now an inescapable event,wreaking havoc and causing massive loss of life and property.The majority of the floodwater,h...The Safaga Region(SR)is part of the Red Sea mountain range in Egypt.Catastrophic flash flooding is now an inescapable event,wreaking havoc and causing massive loss of life and property.The majority of the floodwater,however,has been wasted as runoff to the Red Sea,which,if used wisely,could meet a fraction of the water demands for a variety of applications in this area.The current work aims to use GIS techniques to integrate remote sensing data for evaluating,mitigating,and managing flash floods in SR.The data set comprised Tropical Rainfall Measuring Mission(TRMM)thematic rainfall data,1:50,000 scale topographical map sheets,geological maps,the ASTER Digital Elevation Model(ASTER GDEM),Landsat 7 Enhanced Thematic Mapper"(ETM7+),and Landsat 8 Operational Land Imager.The flash flood risk model of SR is developed using ArcGIS-10.3 geoprocessing tools integrating all the causal factors thematic maps.The final flood risk model for the SR suggests that 57%of the total basins in the SR are at high risk of flooding.Almost 38%of all basins are at moderate flood risk.The remaining 5%of basins are less prone to flooding.Flood-prone zones were identified,suitable dam-building sites were located,and extremely probable areas for water recharge were recognized.On the basis of reliable scientific data,structural and non-structural mitigation strategies that might reduce the damage susceptibility,alleviate the sensitivity of the flash flood,and best utilize its water supply were recommended.展开更多
Flash floods are a natural disaster that occurs annually, especially in the mountainous terrain and steep slopes of northern Thailand. The current flood forecasting systems and tools are available but have low accurac...Flash floods are a natural disaster that occurs annually, especially in the mountainous terrain and steep slopes of northern Thailand. The current flood forecasting systems and tools are available but have low accuracy and efficiency. The numbers of rainfall and runoff stations are less, because the access to the station area is difficult. Additionally, the operation and maintenance costs are high. Hydrological modeling of a SWAT （Soil and Water Assessment Tool） was used in this study with the application of three days weather forecast from the NWP （numerical weather prediction）, which provided temperature, relative humidity, rainfall, sunshine and wind speed. The data from NWP and SWAT were used to simulate the runoff from the Nan River in the last 10 years （2000-2010）. It was found that the simulated flow rate for the main streams using data from NWP were higher than the observations. At the N64 and Nl stations, the ratios of the maximum simulated flow rate to the observations were equal to 108% and 118%, respectively. However, for the tributaries, it was found that the simulated flow rate using NWP data was lower than the observations, but, it was still within the acceptable range of not greater than 20%,6. At N65, D090201 and D090203 stations, the ratio of the maximum simulated flow rate were 90.0%, 83.0% and 86.0%, respectively. This was due to the rainfall from the NWP model being greater than the measured rainfall. The NWP rainfall was distributed all over the area while the rainfall data from the measurements were obtained from specific points. Therefore, the rain from the NWP model is very useful especially for the watershed areas without rain gauge stations. In summary, the data from the NWP can be used with the SWAT model and provides relatively sound results despite the value for the main river being slightly higher than the observed data. Consequently, the output can be used to create a flood map for flash flood warning in the area.展开更多
Critical rainfall estimation for early warning of rainstorm-induced flash flood is an inverse rainstorm-runoff process based on warning discharge threshold for a warning station of interest in a watershed. The key asp...Critical rainfall estimation for early warning of rainstorm-induced flash flood is an inverse rainstorm-runoff process based on warning discharge threshold for a warning station of interest in a watershed. The key aspects of critical rainfall include rainfall amount and rainfall duration. Storm pattern affects highly the estimation of critical rainfall. Using hydrological modeling technique with detailed sub-basin delineation and manual for design rainstorm-runoff computation, this study first introduced basic concept and analysis methods on critical rainfall for flash flood early warning, then, investigated the responses of flash flood warning critical rainfall to storm pattern. Taking south branch of Censhui watershed in China as an example, critical rainfall in case of typical storm patterns for early warning of rainstorm-induced flash flood were estimated at 3 warning stations. This research illustrates that storm pattern plays important role in the estimation of critical rainfall and enough attention should also be paid to storm pattern when making a decision on whether a warning to be issued or not.展开更多
Southern Red Sea flooding is common. Assessing flood-prone development risks helps decrease life and property threats. It tries to improve flood awareness and advocate property owner steps to lessen risk. DEMs and top...Southern Red Sea flooding is common. Assessing flood-prone development risks helps decrease life and property threats. It tries to improve flood awareness and advocate property owner steps to lessen risk. DEMs and topography data were analyzed by RS and GIS. Fifth-through seventh-order rivers were studied. Morphometric analysis assessed the area’s flash flood danger. NEOM has 14 catchments. We determined each catchment’s area, perimeter, maximum length, total stream length, minimum and maximum elevations. It also uses remote sensing. It classifies Landsat 8 photos for land use and cover maps. Image categorization involves high-quality Landsat satellite images and secondary data, plus user experience and knowledge. This study used the wetness index, elevation, slope, stream power index, topographic roughness index, normalized difference vegetation index, sediment transport index, stream order, flow accumulation, and geological formation. Analytic hierarchy considered all earlier criteria (AHP). The geometric consistency index GCI (0.15) and the consistency ratio CR (4.3%) are calculated. The study showed five degrees of flooding risk for Wadi Zawhi and four for Wadi Surr, from very high to very low. 9.16% of Wadi Surr is vulnerable to very high flooding, 50% to high flooding, 40% to low flooding, and 0.3% to very low flooding. Wadi Zawhi’s flood risk is 0.23% high, moderate, low, or extremely low. They’re in Wadi Surr and Wadi Zawhi. Flood mapping helps prepare for emergencies. Flood-prone areas should prioritize resilience.展开更多
Critical rainfall for flash flood early warning is a converse result of precipitation-runoffprocess based on warning discharge threshold for a warning station of interest in a watershed; the key aspects of critical ra...Critical rainfall for flash flood early warning is a converse result of precipitation-runoffprocess based on warning discharge threshold for a warning station of interest in a watershed; the key aspects of critical rainfall include rainfall amount and rainfall duration Using hydrological modeling technique with detailed sub-basin delineation and manual for design precipitation-runoff computation, this study introduces basic concept and methods of analyzing critical rainfall for flash flood early warning. Taking South Branch of Censhui watershed in China as an example, typical critical rainfalls for flash flood dynamic early warning were estimated for 3 warning stations located in the watershed. This research illustrates that detailed watershed characteristics in the context of several warning stations can be modeled in-depth by further delineating the watershed into smaller sub-basins to simulate spatial distribution of various basin parameters. It further confirms that time of concentration of a watershed is an important factor to rainfall duration determination, and the antecedent soil moisture condition of a watershed has significant impact on critical rainfall for same rainfall duration.展开更多
基金Basic Scientific Research Expense Project of IWHR-Extreme rainstorm development trends and prediction techniques,Grant/Award Number:JZ0145B142024National Natural Science Foundation of China,Grant/Award Number:42271095。
文摘Among natural disasters,flash floods are the most destructive events,causing signif-icant damage to the economy and posing a serious threat to human life and property.Comprehensive risk assessment of these sudden floods is a key strategy to mitigate their impact.Accurate analysis of flash flood hazards can greatly enhance prevention efforts and inform critical decision-making processes,ultimately improving our ability to protect communities from these fast-onset disasters.This study analyzed the driving forces of flash flood disaster-causing factors in Heilongjiang Province.Meanwhile,nine different categories of variables affecting the occurrence of flash floods were selected,and the degree of influence of each driving factor on flash floods was quantitatively analyzed,and the driving force analysis of the driving factors of flash floods in Hei-longjiang Province was carried out by using the geographic probe model.This paper employs an uncertainty approach,utilizing a statistical-based interval weight deter-mination technique for evaluation indices and a two-dimensional information-based interval number sorting method.These methodologies are combined to construct a comprehensive flash flood risk assessment model.On this basis,the model was implemented in six regions within China's Heilongjiang province to evaluate and prioritize flash flood risks.The resulting risk ranking for these areas was as follows:Bayan≻Shuangcheng≻Boli≻Suibin≻Hailun≻Yian.The findings demonstrate that the interval number-based evaluation method effectively handles uncertainty,providing a more reliable risk grading system.This approach,by leveraging modern scientific advances and risk quantification techniques,is crucial for improving disaster management and mitigating flash flood impacts.
基金supported by National Natural Science Foundation of Joint Fund for Changjiang River Water Science Research(U2340201)National Natural Science Foundation of China(52239006)Natural Science Foundation of Sichuan Province(2024NSFSC0005).
文摘Rainstorm-induced flood hazards in mountainous areas often result in complex cascading effects by interacting with environmental and human systems.However,traditional studies typically categorize them simply as clearwater floods or debris floods/flows,overlooking their evolutionary characteristics and compound impacts.This study presents a novel classification-based approach to investigate the formation and destructive mechanisms of a catastrophic composite disaster of flash flood and debris flow in the Dayao Gully(DYG)catchment in Hanyuan County,Sichuan Province,China.The event resulted in 14 fatalities,25 missing persons,and extensive infrastructure damage.Through comprehensive field investigations and multi-method analysis,three distinct disaster zones were identified with different magnitudes and impacts:(1)a clearwater flood disaster region with minimal geomorphological changes under a 5-year return period rainfall;(2)a debris flood disaster region triggered by a 30-year return period rainfall,leading to intense sediment transport with a total deposit volume of 52,511 m^(3);and(3)a sediment-induced flood disaster region characterized by significant riverbed aggradation and infrastructure destruction due to sediment-induced blockage effects.The results reveal that the cascading characteristics of this composite disaster were primarily driven by intense rainfall,enhanced sediment transport motivated by supracritical shear stress,and interactions with human infrastructure(e.g.,bridges and buildings).This classification-based approach provides a quantitative assessment of spatial characteristics of cascading flood disasters,offering new insights into their evolutionary characteristics and highlighting the necessity for targeted disaster mitigation strategies in sedimentprone mountainous regions.
基金The Second Tibetan Plateau Scientific Expedition and Research Program,No.2019QZKK0903-02National Key R&D Program of China,No.2022YFC3002902National Natural Science Foundation of China,No.42201086。
文摘The Hengduan Mountains region(HMR)is one of the most densely distributed and severe flash flood disaster-prone areas in southwest China.It is also a key area for major engineering projects and beautiful countryside construction in Southwest China.However,previous studies have not systematically summarized the development characteristics and formation modes of flash flood disasters in the HMR,which limits the development of theoretical and technical system for flood control.In this study,we focused on the physical processes of flash flood disasters in the HMR,including generation,movement,and disaster formation,and clarified the dominant disaster-inducing conditions(multiple humid monsoon circulation,high potential energy and high heterogenous underlying surface)and disaster development characteristics(high spatio-temporal heterogeneity,highly concentrated energy,chain and cascading effects,and clustered occurrence)of flash floods in the HMR.Based on the entire processes of flash flood disasters,three major formation modes have been summarized:the runoff generation mode of vegetation-hydrology-soil coupling dominated by high hydraulic gradient in mountainous areas,strong flow-sediment coupling movement,and serious disaster losses due to high exposure of disaster bearing objects.Finally,based on the issues in previous research,four future research challenges for flash flood disaster in the HMR were proposed.Our study provides insights into disaster prevention and reduction research,including fundamental theoretical system,precise risk assessment of regional disasters,and accurate early warning and forecasting of flash floods.
文摘Flash flood is one of the major meteorological disasters on the Tibet Plateau(TP).Flash flood risk regionalization based on the theory of flash flood occurrence risk is the essential basis for relative risk management.The flash flood risk regionalization and the high-resolution grid mountain flood risk level in TP is carried out by using ArcGIS with the indicators of rainfall,days of heavy rain,vegetation cover,slope,relative elevation difference,river network density,population density,average GDP and traffic density.The areas with high mountain flood risk are mainly located in the middle and downstream of Yarlung,the Nujiang River Valley,the Jinsha River and Lancang River Basin.Besides,the results of flash flood disaster risk regionalization were tested by using historical flash flood disaster data and calamity census data.The disasters occurred in high-risk and sub-high-risk regions are accounted for 73%.Flash floods that cause casualties and economic losses of more than 100,000 CNY(Chinese Yuan)occurred in high-risk areas.Flash flood risk assessment may provide reference for the prevention and control of geological disasters in TP,improve disaster prevention and mitigation capabilities,reduce the hazards of flash floods to social development.
基金jointly supported by the National Key R&D Program of China(Grant Nos.2016YFE0102400 and 2017YFC1502701)the UK-China Research & Innovation Partnership Fund through the Met Office Climate Science for Service Partnership(CSSP) China as part of the Newton Fund
文摘In a globally warming world, subtropical regions are generally expected to become drier while the tropics and mid-high latitudes become wetter. In line with this, Southwest China, close to 25°N, is expected to become increasingly prone to drought if annual mean precipitation decreases. However, despite this trend, changes in the temporal distribution of moisture supply might actually result in increased extreme rainfall in the region, whose climate is characterized by distinct dry and wet seasons. Using hourly and daily gauge observations, rainfall intensity changes since 1971 are exalnined for a network of 142 locations in the region. From the analysis, dry season changes are negligible but wet season changes exhibit a significantly strong downward trend [-2.4% （10 yr）^-1], particularly during the past 15 years [-17.7% （10 yr）^-1]. However, the intensity of events during the wettest of 5% hours appears to steadily increase during the whole period [1.4% （10 yr）^-1], tying in with government statistical reports of recent droughts and flooding. If the opposing trends are a consequence of a warming climate, it is reasonable to expect the contradictory trend to continue with an enhanced risk of flash flooding in coming decades in the region concerned.
基金financial supported by the Iran National Science Foundation(INSF)through research project No.96004000the GIS research group(Ton Duc Thang University)for supports via the research project“GIS-based applications for solving realworld problems”。
文摘Flash floods are responsible for loss of life and considerable property damage in many countries.Flood susceptibility maps contribute to flood risk reduction in areas that are prone to this hazard if appropriately used by landuse planners and emergency managers.The main objective of this study is to prepare an accurate flood susceptibility map for the Haraz watershed in Iran using a novel modeling approach(DBPGA)based on Deep Belief Network(DBN)with Back Propagation(BP)algorithm optimized by the Genetic Algorithm(GA).For this task,a database comprising ten conditioning factors and 194 flood locations was created using the One-R Attribute Evaluation(ORAE)technique.Various well-known machine learning and optimization algorithms were used as benchmarks to compare the prediction accuracy of the proposed model.Statistical metrics include sensitivity,specificity accuracy,root mean square error(RMSE),and area under the receiver operatic characteristic curve(AUC)were used to assess the validity of the proposed model.The result shows that the proposed model has the highest goodness-of-fit(AUC=0.989)and prediction accuracy(AUC=0.985),and based on the validation dataset it outperforms benchmark models including LR(0.885),LMT(0.934),BLR(0.936),ADT(0.976),NBT(0.974),REPTree(0.811),ANFIS-BAT(0.944),ANFIS-CA(0.921),ANFIS-IWO(0.939),ANFIS-ICA(0.947),and ANFIS-FA(0.917).We conclude that the DBPGA model is an excellent alternative tool for predicting flash flood susceptibility for other regions prone to flash floods.
基金supported by the Specific Research of China Institute of Water Resources and Hydropower Research (Grant Nos. Fangji 1240)Chinese Ministry of Water Resources (Grant Nos. 201301058 and 20131059)the Basic Research Fund for Central Public Research Institutes (Grant No. CKSF2015010/TB)
文摘In recent years, flash flood disasters have occurred frequently in southwest China due to the increased frequency of extreme climate events. To solve this problem, great efforts have been made in studying the process of flash flood. However, little attention was paid on bearing body of hazard, the clusters of buildings. Thus the real disaster mechanism of flash flood remains unclear.Accordingly, based on the experiments of artificial flash floods in a conceptual solid model, this paper focuses on the flood-impacted inundation characteristics of the building clusters at different locations of the gully model, in order to obtain a better understanding of the disaster process and the interaction between the flash floods and building clusters. The results showed that, in a typical smallscale flash flood gully with hot and dry climate, 1)clusters of buildings on an alluvial fan could reduce about 35% of the flooding area by blocking the diffusion of the flood to the depression areas, and could also promote the deposition in lower reaches of the river channel by blocking the overbank flow from going back into the channel, making the width-depth ratio of the channel larger. 2) The flash flood rates of disaster and hazard on the alluvial fan are generally higher than that of the inner gully. For the inner gully,buildings located on the beaches along the lower river and the transitional areas of the straight channel and channel bends can easily be affected because of their lower elevations. For the alluvial fan, buildings nearby the meanders suffer the greatest impacts because of bank collapsing and flooding. 3) The safe vertical distance from a building to the river channel is 13 m for the buildings in the inner gully under extreme floods. Below this threshold, the smaller the vertical distance is, the greater the risk exposure is. For the buildings on the alluvial fan, especially for the buildings near the concave bank of the top rush point,the horizontal distance is more important, and the safe value is 80 m under extreme floods.
基金supported by the Key Project in the National Science and Technology Pillar Program during the Twelfth Five-Year Plan Period(Grant No.2012BAK10B04)the Specific Research Fund of the China Institute of Water Resources and Hydropower Research(Grant No.JZ0145B032014)
文摘Flash flood hazard mapping is a supporting component of non-structural measures for flash flood prevention. Pilot case studies are necessary to develop more practicable methods for the technical support systems of flash flood hazard mapping. In this study, the headwater catchment of the Xiapu River Basin in central China was selected as a pilot study area for flash flood hazard mapping. A conceptual distributed hydrological model was developed for flood calculation based on the framework of the Xinanjiang model, which is widely used in humid and semi-humid regions in China. The developed model employs the geomorphological unit hydrograph method, which is extremely valuable when simulating the overland flow process in ungauged catchments, as compared with the original Xinanjiang model. The model was tested in the pilot study area, and the results agree with the measured data on the whole. After calibration and validation, the model is shown to be a useful tool for flash flood calculation. A practicable method for flash flood hazard mapping using the calculated peak discharge and digital elevation model data was presented, and three levels of flood hazards were classified. The resulting flash flood hazard maps indicate that the method successfully predicts the spatial distribution of flash flood hazards, and it can meet the current requirements in China.
基金funded by Vietnam National Foundation for Science and Technology Development (NAFOSTED)under Grant No.105.08-2019.03.
文摘Flash floods are one of the most dangerous natural disasters,especially in hilly terrain,causing loss of life,property,and infrastructures and sudden disruption of traffic.These types of floods are mostly associated with landslides and erosion of roads within a short time.Most of Vietnamis hilly and mountainous;thus,the problem due to flash flood is severe and requires systematic studies to correctly identify flood susceptible areas for proper landuse planning and traffic management.In this study,three Machine Learning(ML)methods namely Deep Learning Neural Network(DL),Correlation-based FeatureWeighted Naive Bayes(CFWNB),and Adaboost(AB-CFWNB)were used for the development of flash flood susceptibility maps for hilly road section(115 km length)of National Highway(NH)-6 inHoa Binh province,Vietnam.In the proposedmodels,88 past flash flood events were used together with 14 flash floods affecting topographical and geo-environmental factors.The performance of themodels was evaluated using standard statisticalmeasures including Receiver Operating Characteristic(ROC)Curve,Area Under Curve(AUC)and Root Mean Square Error(RMSE).The results revealed that all the models performed well(AUC>0.80)in predicting flash flood susceptibility zones,but the performance of the DL model is the best(AUC:0.972,RMSE:0.352).Therefore,the DL model can be applied to develop an accurate flash flood susceptibility map of hilly terrain which can be used for proper planning and designing of the highways and other infrastructure facilities besides landuse management of the area.
基金supported by the National Natural Science Foundation of China[Grant No.41977392]the National Key R&D Program of China[Grant No.2019YFA0606602]+2 种基金the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDA20090000)Qilian Mountain National Park Qinghai Province management bureaufinanced by the China Scholarship Council。
文摘In China,flash floods are one of the main natural disasters causing loss of life and damage to infrastructure.The threat of flash floods is exacerbated with climate change and increased human activities,such that the number of disasters has shown a clear upward trend in recent years.However,due to the scarcity of instrumental data or overly short timeseries,we are still lacking critical data to understand spatio-temporal patterns and driving factors of extreme flash floods.This missing knowledge is however crucial for a proper management of these hazards,especially in remote mountain environments.In forested catchments,dendrogeomorphology allows the reconstruction of past process activity based on growth disturbances(GDs)in trees that have been affected by past flash floods.Therefore,in our study,for the first time,we reconstruct past flash floods in the Qilian Mountains,northeast Tibetan Plateau,over past centuries.To this end,we sampled 99 Qinghai spruce(Picea crassifolia)trees affected by flash floods,with a total of 194increment cores,and identified 302 GDs induced by past flash floods.These GDs have been caused by at least 21 flash floods that we are able to reconstruct over the last 170 years.The position of GDs within tree rings and the intra-seasonal dating of past events also allowed discussion of the likely synoptic situations that may have led to the triggering of flash floods in the past.Logistic regression analysis confirms that significant correlation exists between cumulative maximum 5-day August-September precipitation and reconstructed flash floods,which is corresponding to the majority of scars and related tangential rows of traumatic resin ducts(TRDs)found in the latewood portion of growth rings.These results support the idea that abundant precipitation occurring at the end of the summer season and early fall is the key factor driving flash floods in our study area.Our research not only fills the gaps regarding historical flash flood histories in the Qilian Mountains,but also provides a scientific basis for the region's response to climate change and flood prevention and reduction.
基金the key project of National Natural Science Foundation of China(No.50739002)
文摘Flash floods result from a complex interaction among hydro-meteorological, hydrological, and hydraulic processes across various spatial and temporal scales. Sichuan Province suffers flash floods frequently owing to mountain weather and topography. A flash flood and gravel bed load transport are two key relative problems in mountain river engineering. Bed materials are often encountered in alternate scouring and deposition in mountain fluvial processes during a flash flood. In this circumstance, CRS-1 bed load numerical model jointly with scale physical model is employed to predict water level and gravel bed scour and deposition for design of flood control dykes and flash flood disaster mitigation. A case study on the mechanism of a flash flood disaster induced by bed load transport for a hydropower station in Sichuan Province is conducted. Finally, suggestions to protect the hydropower station are proposed.
基金funded by the National Key R&D Program of China(Grant No.2018YFD1100401)the National Natural Science Foundation of China(Grant No.41925030)+3 种基金the National Natural Science Foundation of China(Grant No.42007270)the Sichuan Science and Technology Program(Grant No.2019YJ0009)the Youth Innovation Promotion Association CAS(2022379)the Chinese Academy of Sciences(CAS)Light of West China Program。
文摘Damage to rural buildings in mountainous regions caused by flash floods accounts for a significant proportion of economic losses from disasters.The unreinforced masonry(URM)wall is the most vulnerable structural element of rural buildings exposed to flash floods.The failure of a URM wall indicates damage to rural buildings in flash floods.Based on the yield line theory of out-of-plane damage of URM walls and the virtual work method,brittle failure criteria for URM walls under the impact of flash floods were established.According to the field investigation data of the 26 June 2020 flash flood event in Damawu Gully and the corresponding simulation results of FLO-2D,the disaster-causing process was analysed,and the failure criteria were validated.Three building parameters were identified to influence the flood-resistance of URM walls,including the mortar grade,the span-to-height ratio of the wall,and the number of floors of the rural building.The results showed that the cause of the 26June disaster was the diversion of a 50-year flash flood into the residential community on the alluvial fan.The affected buildings were constructed with hollow blocks and lacked flood-resistance reinforcement.The critical failure depth of a URM wall restrained at the top by ring beams(RBs)under hydrostatic load conditions is 1.17 to 1.20 times greater than that of a URM wall without RBs,and the difference is even more pronounced when lowerstrength mortar is used.The flood-resistance of a URM wall constructed with Mb 7.5 mortar and restrained by RBs is almost as strong as that of a URM wall constructed with Mb 20 mortar and without RBs.The span-to-height ratio of a URM wall should not be greater than 1.875 in this case.However,the flood-resistance of a URM wall with RB restraint is almost independent of the span-to-height ratio.The brittle fracture energy of masonry mortar is more crucial to the flood-resistance of 4-edge restrained URM walls if L/Z>1.875.The flood-resistance of the URM wall of the first storey increases linearly with the number of floors.Single-storey rural buildings should be given priority to the use of high-grade masonry mortar and high-density blocks to improve flood-resistance.The failure criteria and the influence laws of building parameters on the flood-resistance of URM walls can provide references for flash flood mitigation and flood-resistance reinforcement of rural buildings in mountainous regions of Southwest China.
基金National Natural Science Foundation of China,No.41871164。
文摘In the context of climate change and human activities,flood disasters in arid mountainous areas have become increasingly frequent,and seriously threatened the safety of people's lives and property.Rapid and accurate flash flood inundation modelling is an essential foundational research area,which can aid in the reduction of casualties and the minimization of disaster losses;however,this modelling is also very difficult,and models need to be urgently developed to address flash flood forecasting and warnings.The objective of this study is to construct a numerical modelling method for flash floods in drylands.Based on a 2D high-resolution flood numerical model(Flood Map-Hydro Inundation2D),we hindcasted the dynamic process of flash flooding and show the spatio-temporal characteristics of flash flood inundation for the“8·18”flash flood disaster that occurred in Datong county,Qinghai province.The results showed that the model output effectively agreed with the observed inundation after the event in terms of both spatial extent and temporal process.Extensive flooding mainly occurred between 00:00 and 01:00 on August 18,2022.Qingshan,Hejiazhuang and Longwo villages were affected most heavily.We further conducted model sensitivity analysis and found that the model was highly sensitive to both roughness and hydraulic conductivity in drylands,and the effect of hydraulic conductivity was more pronounced.Our study confirmed the good performance of our model for the simulation of flash flooding in arid areas and provides a potential method for flash flood assessment and management in arid areas.
基金Centre of Geographical Studies,No.UIDB/00295/2020,No.UIDP/00295/2020FCT–Portuguese Foundation for Science and Technology,I.P.,No.SFRH/BD/96632/2013,No.CEEIND/00268/2017Project Be Safe Slide,No.PTDC/GES-AMB/30052/2017。
文摘Water depths and flow velocities decisively influence the damage caused by flash floods.Geographic Information System(GIS)is a powerful and useful tool,allowing the spatial analysis of results obtained by hydraulic modelling,namely from the HEC-RAS/HEC-GeoRAS software.The GIS spatial analysis performed in this study seeks to explain and quantify the spatial relationships between the stream channel features and flow components during flash flood events.Despite these relationships are generically known,there are few studies exploring this subject in different geographic contexts.A 1D hydraulic model was applied in a small watershed in Portugal,providing good results in the definition of floodable areas,water depths and longitudinal velocities.No direct relationship was found between water depths and velocities in the floodable areas;however,negative strong correlations were found between the two flow components along the stream centerlines.Bed slope,channel and flood width,and roughness prove to be highly relevant on the longitudinal variations of water depths and velocities and on the location of maximum values.Increasing peak discharges and return periods(R;)can change the relationships between water depths and velocities at the same location.Results can be improved with more accurate elevation data for stream channels and floodplains.
文摘Morphometric analysis and flash floods assessment were conducted for the watersheds of Ras En Naqb escarpment, south Jordan. The study area comprises of twelve small watersheds occupying the faulted-erosional slopes, and the dip slopes. The drainage network shows that dendritic and sub-dendritic patterns dominated the dip slopes, whereas trellis pattern characterized the faulted-erosional slopes. Stream orders range from fourth to sixth order. The mean bifurcation ratios vary between 4.2 and 5.38 for the dip slope basins, and between 3.5 and 5.0 for the faulted-erosional slope watersheds, indicating a noticeable influence of structural disturbances (i.e., faulting and uplifting), and rejuvenation of drainage networks. All watersheds have short basin lengths, ranging from 23.8 km to 42.2 km for the dip slope basins, and between 15.3 km and 45.4 km for the faulted-erosional slope catchments. This is indicative of high flooding susceptibility associated with heavy rainstorms of short duration. The circularity ratios range from 0.177 to 0.704 which denote that the catchments are moderately circular on the faulted-erosional slopes, and to some extent elongated on the dip slopes. The length of overland flow values ranges from 0.854 to 0.924 for the dip slope catchments, whereas L<sub>O</sub> values for the faulted-erosional slopes vary from 0.793 to 0.945 denoting steep slopes and shorter paths on both dip slope and faulted-erosional slope watersheds. Values of stream frequency range from 1.509 to 1.692 for the dip slope, and from 1.688 to 2.0 for the faulted-erosional slope catchments. F<sub>S</sub> values are also indicative of slope steepness, low infiltration rate, and high flooding potential. The watersheds of the dip slopes show lower values of form factor varying from 0.079 to 0.364, indicating elongated shape and suggesting a relatively flat hydrograph peak for longer duration. Similarly, values of D<sub>d</sub> are high for catchments on the dip slope basins (1.709 - 1.85) and the faulted-erosional slope watersheds (1.587 - 2.0) indicating highly dissected topography, high surface runoff, low infiltration rate, and consequently high flooding potential. Furthermore, high relief values exist, ranging from 388 m to 714 m for the dip slope basins, and from 421 m to 846 m for the faulted-erosional slope catchments indicting high relief and steep slopes. Morphometric analysis, and flash flood assessment suggest that ten watersheds (83.3%) are categorized under high and intermediate flooding susceptibility, and the faulted-erosional slope catchments are more hazardous in terms of flooding. Thus the protection of Ma’an, El Jafr rural Bedouin settlements, and Amman-Aqaba highway from recurrent flooding is essential to ensure sustainable future development in Ras En Naqb-Ma’an area.
基金Open access funding provided by The Science,Technology&Innovation Funding Authority(STDF)in cooperation with The Egyptian Knowledge Bank(EKB)。
文摘The Safaga Region(SR)is part of the Red Sea mountain range in Egypt.Catastrophic flash flooding is now an inescapable event,wreaking havoc and causing massive loss of life and property.The majority of the floodwater,however,has been wasted as runoff to the Red Sea,which,if used wisely,could meet a fraction of the water demands for a variety of applications in this area.The current work aims to use GIS techniques to integrate remote sensing data for evaluating,mitigating,and managing flash floods in SR.The data set comprised Tropical Rainfall Measuring Mission(TRMM)thematic rainfall data,1:50,000 scale topographical map sheets,geological maps,the ASTER Digital Elevation Model(ASTER GDEM),Landsat 7 Enhanced Thematic Mapper"(ETM7+),and Landsat 8 Operational Land Imager.The flash flood risk model of SR is developed using ArcGIS-10.3 geoprocessing tools integrating all the causal factors thematic maps.The final flood risk model for the SR suggests that 57%of the total basins in the SR are at high risk of flooding.Almost 38%of all basins are at moderate flood risk.The remaining 5%of basins are less prone to flooding.Flood-prone zones were identified,suitable dam-building sites were located,and extremely probable areas for water recharge were recognized.On the basis of reliable scientific data,structural and non-structural mitigation strategies that might reduce the damage susceptibility,alleviate the sensitivity of the flash flood,and best utilize its water supply were recommended.
文摘Flash floods are a natural disaster that occurs annually, especially in the mountainous terrain and steep slopes of northern Thailand. The current flood forecasting systems and tools are available but have low accuracy and efficiency. The numbers of rainfall and runoff stations are less, because the access to the station area is difficult. Additionally, the operation and maintenance costs are high. Hydrological modeling of a SWAT （Soil and Water Assessment Tool） was used in this study with the application of three days weather forecast from the NWP （numerical weather prediction）, which provided temperature, relative humidity, rainfall, sunshine and wind speed. The data from NWP and SWAT were used to simulate the runoff from the Nan River in the last 10 years （2000-2010）. It was found that the simulated flow rate for the main streams using data from NWP were higher than the observations. At the N64 and Nl stations, the ratios of the maximum simulated flow rate to the observations were equal to 108% and 118%, respectively. However, for the tributaries, it was found that the simulated flow rate using NWP data was lower than the observations, but, it was still within the acceptable range of not greater than 20%,6. At N65, D090201 and D090203 stations, the ratio of the maximum simulated flow rate were 90.0%, 83.0% and 86.0%, respectively. This was due to the rainfall from the NWP model being greater than the measured rainfall. The NWP rainfall was distributed all over the area while the rainfall data from the measurements were obtained from specific points. Therefore, the rain from the NWP model is very useful especially for the watershed areas without rain gauge stations. In summary, the data from the NWP can be used with the SWAT model and provides relatively sound results despite the value for the main river being slightly higher than the observed data. Consequently, the output can be used to create a flood map for flash flood warning in the area.
文摘Critical rainfall estimation for early warning of rainstorm-induced flash flood is an inverse rainstorm-runoff process based on warning discharge threshold for a warning station of interest in a watershed. The key aspects of critical rainfall include rainfall amount and rainfall duration. Storm pattern affects highly the estimation of critical rainfall. Using hydrological modeling technique with detailed sub-basin delineation and manual for design rainstorm-runoff computation, this study first introduced basic concept and analysis methods on critical rainfall for flash flood early warning, then, investigated the responses of flash flood warning critical rainfall to storm pattern. Taking south branch of Censhui watershed in China as an example, critical rainfall in case of typical storm patterns for early warning of rainstorm-induced flash flood were estimated at 3 warning stations. This research illustrates that storm pattern plays important role in the estimation of critical rainfall and enough attention should also be paid to storm pattern when making a decision on whether a warning to be issued or not.
文摘Southern Red Sea flooding is common. Assessing flood-prone development risks helps decrease life and property threats. It tries to improve flood awareness and advocate property owner steps to lessen risk. DEMs and topography data were analyzed by RS and GIS. Fifth-through seventh-order rivers were studied. Morphometric analysis assessed the area’s flash flood danger. NEOM has 14 catchments. We determined each catchment’s area, perimeter, maximum length, total stream length, minimum and maximum elevations. It also uses remote sensing. It classifies Landsat 8 photos for land use and cover maps. Image categorization involves high-quality Landsat satellite images and secondary data, plus user experience and knowledge. This study used the wetness index, elevation, slope, stream power index, topographic roughness index, normalized difference vegetation index, sediment transport index, stream order, flow accumulation, and geological formation. Analytic hierarchy considered all earlier criteria (AHP). The geometric consistency index GCI (0.15) and the consistency ratio CR (4.3%) are calculated. The study showed five degrees of flooding risk for Wadi Zawhi and four for Wadi Surr, from very high to very low. 9.16% of Wadi Surr is vulnerable to very high flooding, 50% to high flooding, 40% to low flooding, and 0.3% to very low flooding. Wadi Zawhi’s flood risk is 0.23% high, moderate, low, or extremely low. They’re in Wadi Surr and Wadi Zawhi. Flood mapping helps prepare for emergencies. Flood-prone areas should prioritize resilience.
文摘Critical rainfall for flash flood early warning is a converse result of precipitation-runoffprocess based on warning discharge threshold for a warning station of interest in a watershed; the key aspects of critical rainfall include rainfall amount and rainfall duration Using hydrological modeling technique with detailed sub-basin delineation and manual for design precipitation-runoff computation, this study introduces basic concept and methods of analyzing critical rainfall for flash flood early warning. Taking South Branch of Censhui watershed in China as an example, typical critical rainfalls for flash flood dynamic early warning were estimated for 3 warning stations located in the watershed. This research illustrates that detailed watershed characteristics in the context of several warning stations can be modeled in-depth by further delineating the watershed into smaller sub-basins to simulate spatial distribution of various basin parameters. It further confirms that time of concentration of a watershed is an important factor to rainfall duration determination, and the antecedent soil moisture condition of a watershed has significant impact on critical rainfall for same rainfall duration.
