Flood Load Research Articles

Physics-based flood vulnerability assessment for steel portal framed industrial buildings

Steel portal framed industrial buildings have been widely used as warehouses, supermarkets, manufacturing workshops and storage facilities around the world. As such, these buildings make up a significant portion of the building stock. Despite this, there remains a lack of the physics-based flood vulnerability models necessary for undertaking detailed community flood risk management activities (e.g., quantitative risk assessment, cost-benefit analysis of risk reduction and resilience enhancement measures at the building level). To this end, this study developed a physics-based vulnerability assessment method for steel portal framed industrial buildings subjected to hydrostatic and hydrodynamic flood actions. Physical damage induced by flood forces to the building envelope (wall siding and fenestration) and the structural framing (steel portal frames and end wall frames) was considered. Monte Carlo simulations incorporate various flood load cases, probability models of demands and capacities as well as major failure mechanisms of different structural and non-structural components to conduct the damage assessment. The flood vulnerabilities for a prototype industrial building link the physical damage of individual building subassemblies to monetary loss ratios considering various inundation depths, flow velocities and flow directions.

Study on the mechanical characteristics and impact resistance improvement of substation masonry wall under flood load

Study on the mechanical characteristics and impact resistance improvement of substation masonry wall under flood load

Assessing elevated home slab retrofitting method for residential coastal buildings under hurricane loads

With an increase in the frequency and intensity of hurricanes in the United States, effective mitigation solutions should be considered by individuals and governments. This paper investigates the slab elevation retrofit method as a mitigation strategy for residential timber buildings to reduce structural damage and associated economic losses due to hurricane loads. More specifically, a holistic assessment was performed to compare the structural response for typical coastal residential buildings with and without slab elevation incorporated and assess the impact of this retrofitting scheme on the overall building performance. A detailed finite element model was generated for a typical archetype and was used to conduct dynamic analyses for various wind and flood load conditions. The results of the progressive failure analyses were then used to perform loss assessments based on the methodology of the HAZUS hurricane manual. Based on the results of this study, when implementing the slab elevation retrofit method, the damage and associated economic losses due to hurricane-induced loads were reduced. It was observed for all analysis cases that damage due to flood loading dominated the response and economic losses. A noticeable reduction in the recovery time (in days) was also obtained for the considered elevated structures.

Discrete element analysis on impact failure mechanism of “Zhengzhou 7.20” catastrophic flood for coal gangue railway subgrade

Limited research has been conducted on the failure mechanism of coal gangue railway subgrade structures during catastrophic flood disasters, including the impact of varying flood impact heights and load sizes. This study investigates the process and mechanism of coal gangue railway subgrade failure in the coal mining subsidence area, in conjunction with the “7.20” catastrophic flood in Zhengzhou. First, various factors such as impact forms, impact height, flow velocity, water depth, and wave height are considered, and a wave-water flow coupling calculation method is proposed to determine the catastrophic flood load acting on inclined slopes. The maximum impact load calculated is then applied to simulate the impact process of the catastrophic flood using Particle Flow Code 2D. As the flood-related parameters increase, the maximum impact load on the subgrade slope also increases, leading to the breakdown of the subgrade and causing fatal damage. Finally, the failure process of the coal gangue railway subgrade under the impact and scour of a catastrophic flood is divided into three stages: erosion weakening, potential failure surface formation, and overall failure. The main failure mechanisms of each stage are revealed. These research result findings offer valuable insights for the design of railway subgrade reinforcement under catastrophic flood conditions.

Assessing the impacts of reservoirs on downstream hydrological frequency based on a general rainfall-reservoir index

When large reservoirs are built and put into operation, the downstream hydrological processes will be altered significantly, and ecology and agricultural irrigation water of the basin will be affected to some extent. The reservoir index (RI) and the sediment trapping efficiency (TE) of reservoirs are defined to quantify the reservoir impacts on the water flow and sediment by considering the static storage capacity. However, the regulating effect of reservoirs on hydrological variables is not only related to static storage capacity, but also to dynamic reservoir operation. Thus, in this paper, a general rainfall-reservoir index (GRRI) is developed by coupling reservoir regulation indicator (RR, including RI and TE) and effective rainfall affecting the dynamic operation of reservoirs, and the GRRI is used as the covariate to carry out the nonstationary frequency analysis of flood (Q) and annual sediment load (S) at Gaochang (GC) station in Min River, Wulong (WL) station in Wu River, Ankang (AK), Huangjiagang (HJG) and Huangzhuang (HZ) station in Han River, and Cuntan (CT) station on the main stream of the upper Yangtze River. It is found that Q and S at six stations have obvious changes induced by reservoirs, the mean of Q decreases by 22.8%–60.6%, and S drops by 47.7%–89.5% after the change-point of time series. The nonstationary probability distribution models with GRRI as the covariate have better fitting effects than nonstationary models with RR as the covariate. With the incorporation of the impacts of effective rainfall, the GRRI can more accurately capture the occurrence of nonstationarity in the downstream hydrological frequency. These results might be helpful for exploring the impact mechanism of the reservoir regulation on the downstream hydrological variables as well as ecological management of basin.

Rapid Flood Mapping Using Statistical Sampling Threshold Based on Sentinel-1 Imagery in the Barito Watershed, South Kalimantan Province, Indonesia

Flood disasters occur frequently in Indonesia and can cause property damage and even death. This research aimed to provide rapid flood mapping based on remote sensing data by using a cloud platform. In this study, the Google Earth Engine cloud platform was used to quickly detect major floods in the Barito watershed in South Kalimantan province, Indonesia. The data used in this study were Sentinel-1 images before and after the flood event, and surface reflectance of Sentinel-2 images available on the Google Earth Engine platform. Flooding is detected using the threshold method. In this study, we determined the threshold using the Otsu method and statistical sampling thresholds (SST). Four SST scenarios were used in this study, combining the mean and standard deviation of the difference backscatter of Sentinel-1 images. The results of this study showed that the second SST scenario could classify floods with the highest accuracy of 73.2%. The inundation area determined by this method was 4,504.33 km2. The first, third and fourth SST scenarios and the Otsu method could reduce the flood load with an overall accuracy of 48.37%, 43.79%, 55.5% and 68.63%, respectively. The SST scenario is considered to be a reasonably good method for rapid flood detection using Sentinel-1 satellite imagery. This rapid detection method can be applied to other areas to detect flooding. This information can be quickly produced to help stakeholders determine appropriate flood management strategies.

The behavior of the historical Çobandede bridge under flood load

Determination of the structural behavior of historical monuments under different loading types is a crucial task for the preservation and conservation of these structures for transferring to future generations. In this study, the behavior of 800 years old historical Erzurum Çobandede bridge under flood load is investigated. To determine the flood load subjected to the bridge, the best probability distribution model was selected for the observed data obtained from flow gauging stations in the nearby Kağızman Basin and then flood data at different return periods were estimated with this model. The behavior of the bridge under maximum flood load is determined. It is specified that the bridge will not suffer serious damage under the possible maximum flood load in different return periods.

Flood Risk Assessment of Buildings Based on Vulnerability Curve: A Case Study in Anji County

Following the huge economic losses and building damage caused by yearly flooding in China, increased attention to flood risk management within the urban and suburban areas is required. This paper provides an example of the flood risk management of suburban buildings in Anji County. The temporal and spatial characteristics of inundation in the study area are simulated and analyzed based on a verified coupled hydrodynamic model. The vulnerability curve of local masonry buildings to flood risk is established from the theory of structural static mechanics and the empirical equation of flood load. According to the consequences of the hydrodynamic model and vulnerability curve, a flood risk assessment of suburban buildings is conducted. The results show that severe inundation will occur once the dikes are broken. In the 20-, 50-, and 100-year return periods, there are, respectively, 43, 286 and 553 buildings at extremely high risk, distributed in almost each building region. Over half involved buildings are high risk. Buildings at low-lying lands should worry about the great hydrostatic actions caused by terrible waterlogging. This approach can be popularized in urban, suburban, and rural areas, aimed at frame, masonry and even informal structure. The results can provide a scientific reference for Anji County to reduce the flood loss and enhance the flood resistance.

Multi-hazard coupling vulnerability analysis for buckling failure of vertical storage tank: Floods and hurricanes

As one of the typical multi-hazard natural disasters, floods and hurricanes have caused destructive damage to the process equipment, especially vertical storage tanks, leading to a large number of severe technological accidents in chemical industrial parks. In the present study, aiming at the buckling behavior under the coupling effect of floods and hurricanes, the wind load, flood load, and wave load are analyzed, and the limit state equation of storage tank buckling failure under the coupling effect of floods and hurricanes is established. Then, the load distribution on the tank wall is verified by FLUENT software and the rationality of FLUENT simulation is shown by laboratory experiments of vertical storage tanks. The fragility curves and surfaces are plotted by Monte Carlo Simulation under different wind speeds, considering the effects of flood velocity, flood inundation height, and liquid filling level. The results show that with the increase of wind speed, the influence of flood inundation height on the vulnerability of storage tanks gradually increases, while the influence of flood velocity and filling level on the vulnerability of storage tanks gradually decreases. Flood inundation height is the main disaster parameter affecting the vulnerability of storage tanks. Compared with the case of floods or hurricanes alone, the buckling failure probability of storage tanks under the coupling effects of floods and hurricanes increases by 17.67% and 80.50%, respectively. Moreover, the damaging effect of the coupling of floods and hurricanes is greater than that of the direct superposition effect, and the failure probability increases by 17.57%. The research aims to analyze the failure mechanism of vertical storage tanks, accident prevention, and control under the coupling effects of multiple hazards.

Use of fluid structure interaction technique for flash flood impact assessment of structural components

AbstractPrediction of the initial impact force is a major task associated with flood damage assessment of structures subjected to flash flooding especially due to dam break and levee breach. Investigation of failure modes such as overturning and sliding due to soil scouring or erosion is not relevant if the structure first fails by the massive initial dynamic impact. Therefore, a careful assessment of the initial flood impact is critical for the design of structures and during the flood damage assessment process. In most of the past flood damage studies, total flood load acting on the structures was estimated by maximum velocities and water depths obtained from the two‐dimensional hydrodynamic models or the field data. The outcome of these results has shown potential uncertainty in current methods. We present a new approach to calculate the load on structural components impacted by a dam break wave, by modelling the three‐dimensional free surface fluid–structure interaction (FSI) using the incompressible computational fluid dynamics (ICFD) techniques. Two experimental datasets available in the literature are used to validate the results. Finally, we conclude that FSI/IFCD method can be used to accurately determine the initial impact force on structural components subjected to flash floods for flood damage assessment.

Numerical Analysis and Strength Evaluation of an Exposed River Crossing Pipeline with Casing Under Flood Load

Pipelines in service always experience complicated loadings induced by operational and environmental conditions. Flood is one of the common natural hazard threats for buried steel pipelines. One exposed river crossing X70 gas pipeline induced by flood erosion was used as a prototype for this study. A mechanical model was established considering the field loading conditions. Morison equations were adopted to calculate distributional hydrodynamic loads on spanning pipe caused by flood flow. Nonlinear soil constraint on pipe was considered using discrete nonlinear soil springs. An explicit solution of bending stiffness for pipe segment with casing was derived and applied to the numerical model. The von Mises yield criterion was used as failure criteria of the X70 pipe. Stress behavior of the pipe were analyzed by a rigorous finite element model established by the general-purpose Finite-Element package ABAQUS, with 3D pipe elements and pipe-soil interaction elements simulating pipe and soil constraints on pipe, respectively. Results show that, the pipe is safe at present, as the maximum von Mises stress in pipe with the field parameters is 185.57 MPa. The critical flow velocity of the pipe is 5.8 m/s with the present spanning length. The critical spanning length of the pipe is 467 m with the present flow velocity. The failure pipe sections locate at the connection point of the bare pipe and the pipe with casing or the supporting point of the bare pipe on riverbed.

Characterization of a flood-associated deposit on the Waipaoa River shelf using radioisotopes and terrigenous organic matter abundance and composition

An ephemeral oceanic-flood deposit adjacent to a well-studied small mountainous river (SMR), the Waipaoa River in northeastern New Zealand, was characterized using multiple proxies, including radioisotopes (234Th, 7Be, and 210Pb), bulk organic carbon abundance and isotopic signature (%OC, δ13C), as well as a biomarker of terrigenous organic matter (lignin). Field sampling was conducted within two weeks after a 1-in-8 year flood that occurred between January 30 and February 6, 2010. Geochemical analyses indicated that initial deposition of fresh riverine material extended alongshore to the north and south from the river mouth. A comparison of prior- and post-flood 7Be inventories revealed that flood sediments were widely dispersed between 20 and 70m water depth, accounting for 50–80% of the estimated flood load. Surface (0–2cm) isotopic carbon values increased with distance from Poverty Bay, positively correlating with total 210Pb activities, potentially reflecting increasing marine influence with water depth. Abundances of sedimentary organic carbon (OC) were 0.18–0.76% dry weight, and the total nitrogen varied from 0.02 to 0.13%. Stable isotope signatures of carbon (δ13COC), nitrogen (δ15N), and lignin abundances (λ6) throughout the study area ranged from −23.6 to −27.7‰, 1.9 to 5.3‰, and 0.93 to 9.0mg 100mg OC−1, respectively. The spatial distribution pattern of terrigenous organic matter (OM) abundance and interclass ratios (indicative of freshness of organic matter) varied along and across-shelf. Lignin abundances were high and interclass ratios were low in the southern depocenter and inner shelf areas, suggesting that this zone had recently received vascular-plant enriched OM, minimally altered by shelf-bed mixing processes. In contrast, sediments in the northern depocenter and outer shelf also contained elevated amounts of terrigenous sedimentary OM, but this material was generally lower in lignin abundance and had higher interclass ratios (greater degradation). Collectively, these results suggest that the flood-derived sediment and fresh terrigenous OM were mostly constrained between 20 and 70m water depth, with enhanced deposition overlapping the tectonic-controlled depocenters located to the northeast and southeast of Poverty Bay.

The Study on Damage Failure of Pipeline under Flood Using Entropy Identification Method

The buried pipeline will be spanning and subject to dynamic load under flooding, which may induce a damage failure of pipeline. In this paper, a mechanical analysis model of spanning pipelines is established under different levels of flood load. The mechanical response and the information entropy based on strain energy of the pipeline are calculated through global analytical searching method. In addition, the recognition of damage failure of pipeline is achieved according to the value of strain energy entropy of pipeline under different flood levels. The study shows that the strain energy entropy varies with the change of deformation reflects the damage failure feature of pipeline well, which can be used as a new method to identify the failure of pipeline.

Investigation of piping material

The grain size distribution of the material washed out from the piping under flood load, newer investigated earlier. Using 20 samples originating from different places at Danube and Tisza rivers, the grading characteristics of these samples were investigated on the basis of some selected grain sizes and the uniformity gradients. Based on these investigations it has become possible to identify which grain size fractions are likely to be washed out, and to characterise those fractions whose washing out is not expected. Based on the grain size distribution curves it has been made possible to define the boundaries of the zone susceptible to piping. The zone limits of granular soils liquefied by earth quakes and the zone limits of the soil outwashed from piping are very similar. This apparent correspondence already formerly raised the hypothetic question of whether piping occurring during high flood can be simulated by shape to similar surface liquefaction phenomena experienced during earth quakes, as in both cases a volcanic cone is formed through the crater of which water is constantly issuing, dragging away solid particles. Recently the apparent similarity of the zones of grain size distribution curves in the two cases strongly suggest that the two phenomena should indeed be closely related.

Assessing the potential underestimation of sediment and nutrient loads to the Great Barrier Reef lagoon during floods

Much of the sediment and nutrient load to the Great Barrier Reef (GBR) lagoon happens during over bank floods, when discharge can be significantly underestimated by standard river gauges. This paper assesses the potential need for a flood load correction for 28 coastal rivers that discharge into the GBR lagoon. For each river, daily discharge was divided into flows above and below a ‘flood’ threshold to calculate the mean annual percentage flow above this threshold. Most GBR rivers potentially need a flood load correction as over 15% of their mean annual flow occurs above the minor flood level; only seven rivers need little/no correction as their flood flows were less than 5% of the mean annual flow. Improved assessment of the true load of materials to the GBR lagoon would be an important contribution to the monitoring and reporting of progress towards Reef Plan and associated marine load targets.

Modeling on flash flood disaster induced by bed load

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.

Impact of Austrian hydropower plants on the flood control safety of the Hungarian Danube reach

Statistical analysis of daily water level data from four gauging stations along the Hungarian Danube reach has been carried out with the purpose of analysing the impact of the Austrian hydropower plants on the floods of the river. Conditional probability distribution functions of annual flood load maxima and annual number of floods were generated for the periods 1957–1976 and 1977–1996. By comparing these distribution functions, it could be shown that the flood load maxima have decreased, while the number of small and medium floods have increased during the past forty years. These changes indicate a decreased rate of flood superposition resulting from the barrages constructed in this period. The significantly decreased flood load maxima indicate that the Austrian barrage system has a positive impact on the flood control safety of the Hungarian Danube reach.