Simulation Of Flood Events Research Articles

Identification of damage parameters during flood events applicable to multi-span bridges

During flood events, the dynamic interaction between flowing water and bridges generates random loadings that force bridges to vibrate in all six degrees of freedom. It is difficult for a structural damage detection method to select a degree of freedom, or damage feature, to accurately describe and predict damage. The methodology presented here identifies damage-sensitive features and uses them to monitor bridge health. A small-scale physical model of a multi-span highway bridge was constructed to satisfy geometrical, Cauchy, and Froude similarities, and six-dimensional hydrodynamic forces induced by simulated flood events were investigated as an input excitation in a tilting flume. It was determined that pitch, roll, and surge motions can be used as damage features during the inundated stage, while pitch, roll, surge, and heave can be used before the inundated stage. In addition, angular velocity signals exhibited more consistent damage indices than acceleration. Using the damage features, the proposed algorithm could successfully detect damage and damage severity during simulated flood stages. Identifying damage features can reduce the size of the collected data and inform emergency responders’ decisions. This case study can be used to test methods at full scale on similar structures to develop automated health-monitoring systems.

Toward Global Stochastic River Flood Modeling

AbstractGlobal flood models integrate flood maps of constant probability in space, ignoring the correlation between sites and thus potentially misestimating the risk posed by extreme events. Stochastic flood models alleviate this issue through the simulation of flood events with a realistic spatial structure, yet their proliferation at large scales has historically been inhibited by data quality and computer availability. In this paper, we show, for the first time, the efficacy of modeled river discharge reanalyses in the characterization of flood spatial dependence in the absence of a dense stream gauge network. While global hydrological models may show poor correspondence with absolute observed river flows, we find that the rate at which they can simulate the joint occurrence of relative flow exceedances at two given locations is broadly similar to when a gauge‐based statistical model is used. Evidenced over the United States, flood events simulated using observed gauge data from the U.S. Geological Survey versus those generated using modeled streamflows have similar (i) distributions of site‐to‐site correlation strength, (ii) relationships between event size and return period, and, importantly, (iii) loss distributions when incorporated into a continental‐scale flood risk model. Extremal dependence is generally quantified less accurately on larger rivers, in arid climates, in mountainous terrain, and for the rarest high‐magnitude events. However, local‐scale errors are shown to broadly cancel each other out when combined, producing an unbiased flood spatial dependence model. These findings suggest that building accurate stochastic flood models worldwide may no longer be a distant aspiration.

Data-Driven Modeling and the Influence of Objective Function Selection on Model Performance in Limited Data Regions.

The identification of unit hydrographs and component flows from rainfall, evapotranspiration and streamflow data (IHACRES) model has been proven to be an efficient yet basic model to simulate rainfall–runoff processes due to the difficulty in obtaining the comprehensive data required by physical models, especially in data-scarce, semi-arid regions. The success of a calibration process is tremendously dependent on the objective function chosen. However, objective functions have been applied largely in over daily and monthly scales and seldom over sub-daily scales. This study, therefore, implements the IHACRES model using ‘hydromad’ in R to simulate flood events with data limitations in Zhidan, a semi-arid catchment in China. We apply objective function constraints by time aggregating the commonly used Nash–Sutcliffe efficiency into daily and hourly scales to investigate the influence of objective function constraints on the model performance and the general capability of the IHACRES model to simulate flood events in the study watershed. The results of the study demonstrated the advantage of the finer time-scaled hourly objective function over its daily counterpart in simulating runoff for the selected flood events. The results also indicated that the IHACRES model performed extremely well in the Zhidan watershed, presenting the feasibility of the use of the IHACRES model to simulate flood events in data scarce, semi-arid regions.

Sensitivity of urban flood simulations to stormwater infrastructure and soil infiltration

Flooding from intense rainfall is a major hazard in many urban areas. One of the major challenges in urban flood simulations is lack of data about the location and properties of stormwater infrastructure and land cover. In this paper, we investigate the sensitivity of urban flood simulations to inputs of stormwater infrastructure and soil characteristics. We use a 2D hydrodynamic model (MIKE URBAN) to simulate flood events on the University of Alabama (UA) campus in Tuscaloosa U.S.A. Infiltration rate, soil moisture, and soil texture were measured in the field. Soil texture was found to be homogeneous across campus (sandy loam) but with a high degree of spatial and temporal variation in infiltration rate and soil moisture. Comparison between different storm event return periods (10, 25, 50, and 100 years) shows that the same flooding hotspots are persistent but with considerable variation in water depth and flood extent. To investigate the sensitivity of the simulations to stormwater infrastructure, simulations without the stormwater infrastructure input were conducted. The results show that stormwater infrastructure decreases flooding volume of RP 10, 25, 50, and 100 by factors of 20, 14, 12, and 8, respectively. This shows that urban flood simulation is highly sensitive to the inclusion of stormwater infrastructure, though with decreasing relative impact for larger events. To investigate the sensitivity of the simulations to soil characteristics, four land-cover simulations (actual, uniform, entirely pervious, entirely impervious) were compared. The results show flood simulation predictions are sensitive to both the value and spatial explicitness of the soil input data. We discuss challenges in urban flood simulation and their potential solutions in the context of emerging frameworks for national and global hyper-resolution flood forecasting and analysis.

Using radar-based quantitative precipitation data with coupled soil- and groundwater balance models for stream flow simulation in a karst area

A distributed soil water balance model, combined with a lumped karst groundwater model was developed, aiming to simulate stream discharge in karst catchments. Both modelling frameworks, which can be used separately, are presented. They were tested for the Lauchert catchment in the south-west of Germany, using radar based precipitation data, with the focus on simulating flood events. A soil water balance model with 100m grid resolution was combined with groundwater model compartments on a subcatchment base for the catchment covering 450km2. Results show good fits to observed runoff data and could be verified with soil-moisture and groundwater level observations. Specifically, spatially distributed precipitation data has proven to be very helpful for modelling local storm events, which are often not captured by station based weather data. The presented approach is a promising step towards an early warning system for floods in karst catchments.

Merging Satellite and Gauge Rainfalls for Flood Forecasting of Two Catchments Under Different Climate Conditions

As satellite rainfall data has the advantages of wide spatial coverage and high spatial and temporal resolution, it is an important means to solve the problem of flood forecasting in ungauged basins (PUB). In this paper, two catchments under different conditions, Xin’an River Basin and Wuding River Basin, were selected as the representatives of humid and arid regions, respectively, and four kinds of satellite rainfall data of TRMM 3B42RT, TRMM 3B42V7, GPM IMERG Early, and GPM IMERG Late were selected to evaluate the monitoring accuracy of rainfall processes in the two catchments on hourly scale. Then, these satellite rainfall data were respectively integrated with the gauged data. HEC-HMS (The Hydrologic Engineering Center's-Hydrologic Modeling System) model was calibrated and validated to simulate flood events in the two catchments. Then, improvement effect of the rainfall merging on flood forecasting was evaluated. According to the research results, in most cases, the Nash–Sutcliffe efficiency coefficients of the simulated streamflow from initial TRMM (Tropical Rainfall Measuring Mission) and GPM (Global Precipitation Measurement) satellite rainfall data were negative at the two catchments. By merging gauge and TRMM rainfall, the Nash–Sutcliffe efficiency coefficient is mostly around 0.7, and the correlation coefficient is as high as 0.9 for streamflow simulation in the Xin'an River basin. For the streamflow simulated by merging gauge and GPM rainfall in Wuding River basin, the Nash–Sutcliffe efficiency coefficient is about 0.8, and the correlation coefficient is more than 0.9, which indicate good flood forecasting accuracy. Generally, higher performance statistics were obtained in the Xin'an River Basin than the Wuding River Basin. Compared with the streamflow simulated by the initial satellite rainfalls, significant improvement was obtained by the merged rainfall data, which indicates a good prospect for application of satellite rainfall in hydrological forecasting. In the future, it is necessary to further improve the monitoring accuracy of satellite rainfall products and to develop the method of merging multi-source rainfall data, so as to better applications in PUB and other hydrological researches.

Evaluation of the microbial safety and quality of Louisiana strawberries after flooding

Adverse weather such as flooding affects Louisiana strawberry production. Floodwater is an ideal medium for the growth of foodborne pathogens and may cause contamination of soil, water, and fresh produce. To evaluate the microbial safety of strawberries after flooding, four flooding scenarios were investigated. Five raised beds were exposed to a simulated flood event. Treatments included High Flood High Contamination (HFHC), High Flood Low Contamination (HFLC), Low Flood High Contamination (LFHC), Low Flood Low Contamination (LFLC) and a Control (C). High flood groups (HF) were exposed to 890 L of floodwater where strawberries were fully submerged, while low flood groups (LF) were exposed to 600 L of floodwater where strawberries did not come into direct contact with the floodwater. Three strains of generic Escherichia coli were spiked into the floodwater to establish a baseline population of approximately 106 colony forming units per liter (CFU/L) (high contamination) and 102 CFU/L (low contamination). Strawberry plants in all treatments were flooded for 4 h until floodwater receded. Strawberries were harvested when mature and sampled during shelf-life at 4 °C at 0, 48, 96, and 144 h. Soil samples were collected in the field every 48 h for one week. Even though the generic E. coli was not detected (<10 CFU/g) in strawberry samples, it was detected in soil samples within 96 h after flooding. In soil samples, generic E. coli was higher in HFHC samples (1.6 log CFU/g) compared to HFLC samples (1.1 log CFU/g) at harvest. Additionally, 1.0 to 2.8 log CFU/g of coliform were present in the strawberries and soil at 0, 48, 96, and 144 h in all treatment beds.

2D numerical simulation of unsteady flows for large scale floods prediction in real time

The challenge of finding a compromise between computational time and level of accuracy and robustness has traditionally expanded the use simplified models rather than full two-dimensional (2D) models for flood simulation. This work presents a GPU accelerated 2D shallow water model for the simulation of flood events in real time. In particular, an explicit first-order finite volume scheme is detailed to control the numerical instabilities that are likely to appear when used in complex topography. The model is first validated with the benchmark test case of the Toce River (Italy) and numerical fixes are demonstrated to be necessary. The model is next applied to reproduce real events in a reach of the Ebro River (Spain) in order to compare simulation results with field data. The second case deals with a large domain (744 km2) and long flood duration (up to 20 days) allowing an analysis of the performance and speed-up achieved by different GPU devices. The high values of fit between observed and simulated results as well as the computational times achieved are encouraging to propose the use of the model as forecasting system.

Major flood events recorded in the Holocene sedimentary sequence of the uplifted Ladiko and Makrisia basins near ancient Olympia (western Peloponnese, Greece)

Detailed palaeoenvironmental studies were conducted in the Ladiko and Makrisia basins near the Alpheios River and ancient Olympia (western Peloponnese, Greece) to assess major landscape changes during the Holocene. Previous studies and literature data document that the area experienced crust uplift of minimum 13 m to 30 m since the mid-Holocene. Geological archives were sampled along a vibracore transect connecting the Ladiko and Makrisia basins. Sediment cores were analyzed using sedimento-logical, geochemical and micropalaeontological methods. Geochronological reconstruction of major landscape changes is based on a set of 24 radiocarbon dates. Geophysical studies were carried out using electrical resistivity tomography (ERT) and Direct Push-Electrical Conductivity (DP-EC) measurements to detect stratigraphic changes and subsurface bedrock structures. The stratigraphic record of the uplifted lake basins of Ladiko and Makrisia revealed two major lithostratigraphic units. Unit I, predominantly composed of clay, silt and silty fine sand, reflects prevailing low-energy sedimentary conditions typical of quiescent (fluvio-)limnic waterbodies. Unit II is made out of fine to coarse sand and documents repeated interferences of unit I associated with abrupt and temporary high-energy flood type (= heft) events. We found signals of four different heft events (H1 to H4) showing strong stratigraphic and geochronological consistencies along the vibracore transect. The following age ranges were determined: H1 – between 4360 – 4330 cal BC and 4320 – 4080 cal BC; H2 – be- tween 2830 – 2500 cal BC and 2270 – 2140 cal BC; H3 – between 1220 –1280 cal AD and 1290 –1390 cal AD; H4 – between 1640 –1800 cal AD and 1650 –1800 cal AD. Different hypotheses concerning the characteristics, potential trigger mechanisms and causes of the flood events were tested against the background of strong Holocene crust uplift and using a variety of different methodological approaches: Geomorphological and granulometric aspects, micropalaeontological contexts, geochronological data sets, numerical simulation of flooding events, local tectonic uplift, and the palaeoclimate background were taken into account. We hypothesize that, during the mid-Holocene, the study area was affected by tsunami events, namely between 4360 – 4330 cal BC and 4320 – 4080 cal BC (H1) and between 2830 – 2500 cal BC and 2270 – 2140 cal BC (H2). These ages are very well consistent with the supra-regional and regional tsunami event signal retrieved from many coastal archives in large parts of western Greece. The timing of flood events H1 and H2 is highly consistent with ages of (supra-)regional tectonic events known from literature and is not consistent with increased flood indices of palaeoclimate data available for western Greece. Tsunami inundation scenarios based on numerical simulation are highly consistent with vibracoring and geophysical (ERT, DP-EC) data. In contrast, heft events H3 and H4 are possibly related to phases of increased precipi- tation and flooding activity in the Mediterranean or to land-based geomorphological processes triggered by regional tectonic events (RTE). Neolithic, Chalcolithic as well as Early and Middle Helladic human activities documented at ancient Olympia were most probably affected by tsunami heft events H1 and H2. Sandy deposits of tsunami event H2, covering the prehistorical tumulus, seem to have been used as a higher and dry base to construct the apsidal houses in the center of the later sanctuary at Olympia. The site, already abandoned, must have again been subject to major flood events during the 13/14th cent. AD and the 17–19th cent. AD associated with heft events H3 and H4.

A simulation study on effects of suspended sediment through high riverine discharge on surface river plume and vertical water exchange

Rivers transport freshwater and suspended sediment matter (SSM) from land to coastal seas. In coastal seas termed as regions of freshwater influence (ROFIs), SSM is not only passively transported but also changes the density of ambient water and influences the physical characteristics especially in flood events, when a lot of SSM is supplied to the sea. Although the influence of SSM on the physical field in ROFIs would be significant, interactive physical processes, such as dynamics of river plumes and estuarine circulations, have hardly been investigated for hypopycnal plumes (i.e., the riverine sediment-freshwater is not denser than the seawater). In order to quantitatively estimate the interactive effects of SSM, we employ a non-hydrostatic ocean model with Lagrangian particles, which represents SSM and affects the density and buoyancy of ambient water. We use two experimental settings: (1) realistic simulations of the Tango Bay, Japan under the flooding of September 2013 and (2) idealized simulations for an open-bay ROFI. The former is conducted to assess whether the simulations could reproduce an actual event to some extent. The realistic simulations demonstrate that the choice of parameters such as SSM-particle size and composition is important for coastal simulations of flood events. The latter is conducted to understand the basic physics and to study the quantitative sensitivities of the physical processes to the riverine flux, composition, and particle size of SSM. The idealized simulations demonstrate that a large amount of riverine SSM affects the physical field in ROFIs through the following process: 1) horizontal density differences between nearshore and offshore waters are reduced as apparent density is increased close to the river mouth by riverine SSM, 2) the strength of vertical circulation is weakened by the reduced horizontal density difference, and 3) vertical water exchange between the surface and the subsurface layers decreases. The process in the control case of this study increases the relative amounts of surface freshwater in the river plume by 0.8% of the total riverine freshwater input. Sensitivity experiments with changing the parameters of SSM flux into the river, SSM composition, and SSM-particle diameter show that the percentage can be raised up to 2%. Meanwhile, the above-mentioned processes do not apply to extreme cases of small particle size and enormous SSM input wherein homopycnal (i.e., a similar density between the riverine sediment-freshwater and the ambient seawater) and hyperpycnal (i.e., the density of the riverine sediment-freshwater mixture exceeds the ambient seawater) plumes take place.

A full-scale fluvial flood modelling framework based on a high-performance integrated hydrodynamic modelling system (HiPIMS)

Full-scale fluvial flood modelling over large catchments has traditionally been carried out using coupled hydrological and hydraulic/hydrodynamic models. Such a traditional modelling approach is not well suited for the simulation of extreme floods induced by intense rainfall, which is usually featured with highly transient and dynamic rainfall-runoff and flooding process. This work aims to develop and demonstrate a modelling framework to predict the full-scale process of fluvial flooding from the source (rainfall) to impact (inundation) over a large catchment using a single high-performance hydrodynamic model driven by rainfall inputs. The modelling framework is applied to reproduce the flood event caused by the 2015 Storm Desmond in the 2500 km2 Eden Catchment at 5 m resolution. Without intensive model calibration, the predicted results compare well with field observations in terms of inundation extent and gauged water levels across the catchment. Sensitivity tests reveal that high-resolution grid is essential for accurate simulation of fluvial flood events using a 2D hydrodynamic model. Accelerated by multiple modern GPUs, the simulation is more than 2.5 times faster than real time although it involves 100 million computational cells inside the computational domain. This work provides a novel and promising approach to assess and forecast at real time the risk of extreme fluvial floods from intense rainfall.

Spatial downscaling of 3-hourly precipitation forecast data at river basin scale

This study proposes and applies a simple methodology to downscale 3-hourly precipitation data obtained from a large-scale atmospheric model to a finer resolution grid, which is compatible with the scale of the main hydrological processes occurring in a river basin. The aim was to obtain quantitative precipitation forecast data, suitable to be used as an input in rainfall–runoff models to simulate flood events. ERA-Interim forecasts of total precipitation, with 0.75° of spatial resolution, were downscaled by statistical adjustment to a data series of observed precipitation in rain gauges. The adjustment draws on the “Bias-Correction Spatial Downscaling” method, with two modifications: (1) the order in which bias correction is carried out; and (2) the fact that it is applied to the downscaling of higher frequency data (3-hourly precipitation). Relations between the forecasts and the locally observed precipitation were estimated by applying the method of histogram equalization, obtaining piecewise transfer functions with good explanatory power (adjusted R2 above of 0.99). These functions enabled the removal of the systematic bias of ERA-Interim forecasts, improving their overall fit with the observed data. This improvement proved more significant in the prediction of precipitation volumes over time, compared to the forecast of peak values. The methodology was applied to the basin of the largest fully Portuguese river (Mondego), with a grid resolution of 0.125° × 0.125°.

Evaluation of fungicides and biofungicide to control Phytophthora root rot (Phytophthora cinnamomi Rands) and ambrosia beetles (Coleoptera: Curculionidae: Scolytinae) on flowering dogwoods exposed to simulated flood events

Phytophthora root rot causes major economic losses in woody ornamental nurseries, especially in plants exposed to flooding. Ambrosia beetles, which attack stressed trees, are also important pests of woody plants. In this study, several products were evaluated for control of Phytophthora root rot and ambrosia beetles on containerized flowering dogwoods (Cornus florida L.) exposed to simulated flood events under field conditions. In two trials, preventive (7 days preflooding) or curative (1 day postflooding) sprench (combination spray and drench) treatments were applied to containerized dogwoods artificially inoculated with Phytophthora cinnamomi Rands. The plants were flooded by maintaining standing water for 1, 3, or 7 days. After the trials, plant growth data (dry shoot weight, dry root weight, plant height, plant width, caliper) were recorded, and roots were assessed for disease severity using a scale of 0–100% roots affected, as well as plated on PARPH-V8 medium to determine the percentage of Phytophthora-infected root samples. Ambrosia beetle attacks were recorded throughout the study. Longer flooding duration increased disease pressure from Phytophthora cinnamomi Rands. Preventive treatment of plants with Subdue MAXX consistently reduced disease severity at tested flooding durations of 1, 3, or 7 days. Preventively- (before flooding) or curatively- (after flooding) applied treatments of Empress Intrinsic, Orkestra Intrinsic, and Pageant Intrinsic reduced disease pressure at 1 and 3 days of flooding. Preventive RootShield Plus+ treatment reduced disease pressure on plants flooded 1 day. Longer flooding periods as well as Phytophthora cinnamomi inoculation increased ambrosia beetle attacks on flooded dogwoods, but preventively- and curatively-applied Orkestra Intrinsic as well as preventively-applied Subdue MAXX reduced ambrosia beetle attacks compared to non-treated, inoculated controls. These treatments were effective at reducing both Phytophthora and ambrosia beetle damage. These results can help nursery producers successfully manage Phytophtora root rot and also reduce the risk of ambrosia beetle attacks during flood events.

Combination of hydrologic and hydraulic modeling on flood and inundation warning: case study at Tra Khuc-Ve River basin in Vietnam

Flooding caused by historically high flows, especially in Tra Khuc-Ve River basin in the Mid-Central region in Vietnam in November 2013, which caused widespread damage. The purpose of this paper was to establish the inundation maps in the downstream part of Tra Khuc-Ve rivers by using the coupling of the hydrological and hydraulic models (MIKE SHE/MIKE 11 and MIKE 11 GIS). Calibration and validation of the hydrological model were in good agreement in terms of the vibration amplitude, absolute value, and phases. The hydraulic model results showed good agreement between observed and simulated flood events in 2012 and 2013 after calibration and validation. The rainfall forecasting from the IFS model was also used to establish six flood warning scenarios based on the alarm level III (6.5 m) and the historical level (8.76 m). The inundation maps showed the extent of flooding and the water depth in the downstream part of the study area. The simulation results of historical data showed that Tu Nghia and Son Tinh Districts were the most affected areas by inundation with over 11% affected area while Quang Ngai Town inundated 8.1%. The study results will support decision makers in planning to reduce the impacts of natural disasters in Tra Khuc-Ve River basin in the future.

Comparative Performance of Fungicides, Biofungicides, and Host Plant Defense Inducers in Suppression of Phytophthora Root Rot in Flowering Dogwood During Simulated Root Flooding Events.

During flooding events in nurseries, Phytophthora root rot caused by Phytophthora cinnamomi Rands often causes damage that leads to complete crop loss. In this study, we evaluated the efficacy of fungicides, biofungicides, and host plant defense inducers for preventive and curative control of Phytophthora root rot on flowering dogwood (Cornus florida L.) seedlings exposed to a simulated flood event of 1, 3, or 7 days. In two greenhouse trials, preventive (7 days before flooding) or curative (1 day after flooding) drench treatments were applied to dogwood seedlings artificially inoculated with P. cinnamomi. The plants were flooded by maintaining standing water for 1, 3, or 7 days. After the trials, plant growth data (total plant weight, root weight, plant height, and plant width) were recorded, and root systems were assessed for disease severity using a scale of 0 to 100% of roots affected, and subsamples were plated on PARPH-V8 medium to determine the percent recovery of the Phytophthora pathogen. Plants preventively treated with Subdue MAXX had reduced disease severity relative to the nontreated, inoculated plants (positive control) flooded 1, 3, or 7 days in both trials. Pageant Intrinsic and Segovis treatments also had lower disease severity than the positive control at all flooding durations in trial two, but not trial one. In trial one, preventive and curative treatments of Orkestra Intrinsic had reduced disease severity compared with the positive control at 1 and 3 days of flooding, whereas curative treatments of Empress Intrinsic and Tartan Stressgard also were effective at 1 and 3 days of flooding in trial one. The host plant defense inducers (Aliette 80 WDG, Signature Xtra, and Actigard) were inconsistent and ineffective at reducing disease severity when applied as preventive or curative treatments. Preventive treatments of the biofungicides RootShield Plus+ and MBI-110 had consistently lower disease severity than the positive control at 1 day of flooding but not 3 or 7 days of flooding. Potentially, growers can use information from this study to manage Phytophthora root rot during flooding or in areas of the nursery that often experience high soil moisture levels.

Subjective modeling decisions can significantly impact the simulation of flood and drought events

It is generally acknowledged in the environmental sciences that the choice of a computational model impacts the research results. In this study of a flood and drought event in the Swiss Thur basin, we show that modeling decisions during the model configuration, beyond the model choice, also impact the model results. In our carefully designed experiment we investigated four modeling decisions in ten nested basins: the spatial resolution of the model, the spatial representation of the forcing data, the calibration period, and the performance metric. The flood characteristics were mainly affected by the performance metric, whereas the drought characteristics were mainly affected by the calibration period. The results could be related to the processes that triggered the particular events studied. The impact of the modeling decisions on the simulations did, however, vary among the investigated sub-basins. In spite of the limitations of this study, our findings have important implications for the understanding and quantification of uncertainty in any hydrological or even environmental model. Modeling decisions during model configuration introduce subjectivity from the modeler. Multiple working hypotheses during model configuration can provide insights on the impact of such subjective modeling decisions.

River discharge simulation using variable parameter McCarthy–Muskingum and wavelet-support vector machine methods

In this study, an extended version of variable parameter McCarthy–Muskingum (VPMM) method originally proposed by Perumal and Price (J Hydrol 502:89–102, 2013) was compared with the widely used data-based model, namely support vector machine (SVM) and hybrid wavelet-support vector machine (WASVM) to simulate the hourly discharge in Neckar River wherein significant lateral flow contribution by intermediate catchment rainfall prevails during flood wave movement. The discharge data from the year 1999 to 2002 have been used in this study. The extended VPMM method has been used to simulate 9 flood events of the year 2002, and later the results were compared with SVM and WASVM models. The analysis of statistical and graphical results suggests that the extended VPMM method was able to predict the flood wave movement better than the SVM and WASVM models. A model complexity analysis was also conducted which suggests that the two parameter-based extended VPMM method has less complexity than the three parameter-based SVM and WASVM model. Further, the model selection criteria also give the highest values for VPMM in 7 out of 9 flood events. The simulation of flood events suggested that both the approaches were able to capture the underlying physics and reproduced the target value close to the observed hydrograph. However, the VPMM models are slightly more efficient and accurate, than the SVM and WASVM model which are based only on the antecedent discharge data. The study captures the current trend in the flood forecasting studies and showed the importance of both the approaches (physical and data-based modeling). The analysis of the study suggested that these approaches complement each other and can be used in accurate yet less computational intensive flood forecasting.

Simulation of Flood Event in Kelantan on December 2014 as revealed by the HEC-HMS

A devastating flood disaster occurred at Kuala Krai, Kelantan on December 2014. The flood disaster had given a significant destructive impact on the infrastructure and as a result, almost 1,600 homes were lost or destroyed. This extreme flood event killed 25 villages and forced 45,467 people in Kuala Krai, Kelantan to be evacuated from their homes. Continuous heavy rain for over three days from the 21st to the 23rd of December, 2014 was set a rainfall record of 1,295 mm, equivalent to the amount of rain usually seen in a span of 64 days. As a result, the water levels of three major rivers, the Sungai Galas in Dabong, the Sungai Lebir in Tualang and the Sungai Kelantan in Jambatan Gueillemard, rose above the dangerous water levels. It is essential to estimate the extent of flood inundation. The objective of this study is to simulate flood event in December 2014 by using HEC-HMS. The results show the peak discharges and inundations occurred approximately on the 25th December 2014; 18,575.7 m3/s to be almost similar magnitude as reported by DID 2014 Flood Report. These findings led to the conclusion that the HEC-HMS model is useful as a flood analysis tool.

Interaction of a Preventative Fungicide Treatment and Root Rot Pathogen on Ambrosia Beetle Attacks during a Simulated Flood Event.

Flooding can increase tree susceptibility to root rot pathogens as well as attacks by ambrosia beetles attracted to stress-induced ethanol emissions. The objective of this study was to investigate the interaction of a preventative fungicide treatment and root infection with Phytophthora cinnamomi on ambrosia beetle attacks in flood stressed trees. A fungicide (Pageant® Intrinsic®) was evaluated in two flood trials using Eastern redbud and tulip poplar trees with treatments including the fungicide with or without pathogen or no fungicide with or without pathogen. Fungicide treated trees had fewer ambrosia beetle attacks, particularly in trees without P. cinnamomi co-infection. In a follow-up experiment, ethanol content was evaluated in flooded redbuds to determine if the fungicide treatment reduced stress-induced compounds. All flood stressed trees began producing ethanol within 24 h post flooding, regardless of fungicide treatment or P. cinnamomi infection. We conclude that pre-treatments of a fungicide can provide protection from ambrosia beetle attacks during an extreme flood event, but that protection is reduced if a root rot pathogen is also present. Additionally, rejection of fungicide treated trees was not related to the absence of ethanol, as the fungicide-treated plants released ethanol in quantities similar to non-treated trees.

Simulating the Influence of Buildings on Flood Inundation in Urban Areas

Two-dimensional hydraulic modeling is fundamental to simulate flood events in urban area. Key factors to reach optimal results are detailed information about domain geometry and utility of hydrodynamic models to integrate the full or simplified Saint Venant equations in complex geometry. However, in some cases, detailed topographic datasets that represent the domain geometry are not available, so approximations—such as diffusive wave equation—is introduced whilst representing urban area with an adjusted roughness coefficient. In the present paper, different methods to represent buildings and approximation of the Saint Venant equations are tested by performing experiments on a scale physical model of urban district in laboratory. Simplified methods are tested for simulation of a real flood event which occurred in 2013 in the city of Olbia, Italy. Results show that accuracy of simulating flow depth with a detailed geometry is comparable to the one achieved with an adjusted roughness coefficient.