Inland Flooding Research Articles

Development of flood inundation maps as an initial assessment for flood disaster mitigation - a case study of selagan river basin

Flood is a natural disaster that often occurs in Bengkulu Province. One of which occurred at the Selagan River Basin which caused in several sub-districts in Mukomuko District to be flooded. Goverment must be fast and precise in resolving future flooding problems in the Selagan River Basin. In solving the problem, initial assessment data is certainly needed, one of which is a flood inundation map, so that later the infrastructure that is built is right to solve the flooding problem that occurred in the Selagan River basin. This study was conducted to model section of the Selagan River for flood inundation forecasting with the help of digital elevation model (DEM) Data, hydrological data, river characteristics data, geographical information system(GIS). Those data is used to create a flood inundation model that is built with hydrodynamic modules which consist of rainfall runoff module, flood routing and inland flooding by using the MIKE software. Simulations of flood inundation that has been made are compared using inundation observation data at flood locations, so the results of flood inundation maps occur at this time can be a preliminary assessment for flood mitigation in the future.

Evaluation of Real-Time Water Level Prediction Technology Using Statistical Models for Reducing Urban Flood Risk

The frequency of localized short-term torrential rains that exceed the planned rainfall is increasing along with inundation damage due to inland flooding. Stepwise inundation measures utilizing existing stock and disaster prevention/mitigation for excessive rainfall are required. In this study, we describe the results of empirical research using a statistical model constructed based on rainfall and water level observation data as a highly accurate water level prediction method suitable for real-time prediction. This is aimed at application in flood control activities and operation support of pump facilities. By comparing and verifying the prediction accuracy between the water level prediction model and the statistical model by Convolutional Neural Network (CNN), which is generally used as an image recognition technology, the usefulness of the statistical model was confirmed. Further improvement in accuracy and widespread use of these water level prediction models are expected.

Demonstration of Stormwater Management Technology by Short-Term Rainfall Prediction and Real-Time Runoff Analysis System Using Small X-Band Radar

We developed a system that combines urban area rainfall radar (small X-band, dual-polarization radar), short-term rainfall prediction model, and real-time runoff analysis technology, and the demonstration study was conducted on the drainage districts in Fukui City and Toyama City. We demonstrated the effectiveness of the flood damage, by providing the real-time information on rainfall prediction, water level in sewerage pipes, and inland flood prediction to the operators of drainage pump of stormwater storage pipes, and residents in flood-prone areas. During the study for about two years, it was confirmed that the accuracy of the radar rainfall observation was comparable to that of the X-band dual-polarization Doppler weather radar managed by the Ministry of Land, Infrastructure, Transport and Tourism. In the operation of the drainage pump for the Tsukimiminori Stormwater Storage Pipe in Fukui City, we were able to secure the storage capacity for the next rainfall based on the forecast information by maximizing the drainage capacity of the discharge destination. In addition, it was also confirmed that the residents themselves could secure the lead time for setting up water-stop sandbags and moving their vehicles to higher ground.

Impact of Climate Change on Flood Hazard at Airports on Pacific Islands: A Case Study of Faleolo International Airport, Samoa

Climate change is believed to have increased the intensity and frequency of heavy rainfall, and also to have caused sea level rises over this century and beyond. There is widespread concern that small-island nations are particularly vulnerable to increasing risk of inland flood due to such climate change. Understanding the impact of climate change on flood hazard is of great importance for these countries for the development of better protection and adaptation strategies. This study conducted a case study focusing on the impact of climate change on flood hazard at Faleolo International Airport (FIA), Samoa. FIA is a typical small islands airport, located on the lowland along the coast fronted by a fringing reef. Annual maximum daily rainfalls for different return periods were first estimated for the present and future climate around FIA. The estimated rainfalls were input as the forcing of a two-dimensional flood inundation model to investigate the flooding behavior and effectiveness of probable drainage systems. Results showed that a part of the runway can be inundated under heavy rainfall. Construction of drainage pipes significantly contributes to reducing the flood hazard level. Sensitivity analysis showed that the astronomical tide level has relatively little influence on the performance of the drainage system, while the combination of sea level rise and the sea level anomaly induced by stormy waves on the fringing reef could have non-negligible impacts on the drainage system. Location of the drainage pipe is also important to effectively mitigate flooding. The time-concentration of torrential rainfall may also significantly impact the overall performance of the drainage system.

Scenario Analysis of Sluice Gate Operations for Evaluating Inland Flood Damage

Typhoon Hagibis, which hit Japan directly on October 12, 2019, caused great damage, including the flooding of rivers, across various parts of Japan. The Tama River, which flows north of Kawasaki City, also experienced flooding which exceeded the designed high water level; although it did not cause fluvial flooding, river water flowed into the urban areas through the sewerage system, causing unprecedented inundation damage. This damage was reproduced with the inland flood simulation model. Furthermore, we performed simulations in which the water level, precipitation, and sluice gate operation of the Tama River differed from actual conditions, and compared them with the actual damage. Based on these results, we examined methods for reducing inundation damage, such as improving the operation method of sluice gates, and confirmed their effects.

Hurricane Scenario Generation for Uncertainty Modeling of Coastal and Inland Flooding

Hurricanes often induce catastrophic flooding due to both storm surge near the coast, and pluvial and fluvial flooding further inland. In an effort to contribute to uncertainty quantification of impending flood events, we propose a probabilistic scenario generation scheme for hurricane flooding using state-of-art hydrological models to forecast both inland and coastal flooding. The hurricane scenario generation scheme incorporates locational uncertainty in hurricane landfall locations. For an impending hurricane, we develop a method to generate multiple scenarios by the predicated landfall location and adjusting corresponding meteorological characteristics such as precipitation. By combining inland and coastal flooding models, we seek to provide a comprehensive understanding of potential flood scenarios for an impending hurricane. To demonstrate the modeling approach, we use real-world data from the Southeast Texas region in our case study.

Assessment of Flood Forecast Products for a Coupled Tributary-Coastal Model

Compound flooding, resulting from a combination of riverine and coastal processes, is a complex but important hazard to resolve along urbanized shorelines in the vicinity of river mouths. However, inland flooding models rarely consider oceanographic conditions, and vice versa for coastal flood models. Here, we describe the development of an operational, integrated coastal-watershed flooding model to address this issue of compound flooding in a highly urbanized estuarine environment, San Francisco Bay (CA, USA), where the surrounding communities are susceptible to flooding along the bay shoreline and inland rivers and creeks that drain to the bay. The integrated tributary-coastal forecast model (Hydro-Coastal Storm Modeling System, or Hydro-CoSMoS) was developed to provide water managers and other users with flood forecast information beyond what is currently available. Results presented here are focused on the interaction of the Napa River watershed and the San Pablo Bay at the northern end of San Francisco Bay. This paper describes the modeling setup, the scenario used in a tabletop exercise (TTE), and the assessment of the various flood forecast information products. Hydro-CoSMoS successfully demonstrated the capability to provide watershed and coastal flood information at scales and locations where no such information is currently available and was also successful in showing how tributary flows could be used to inform the coastal storm model during a flooding scenario. The TTE provided valuable feedback on how to guide continued model development and to inform what model outputs and formats are most useful to end-users.

Strengthening of elevated home slabs on grade with external fiber-reinforced polymer (FRP) laminate

Concrete slab on grade homes are being increasingly elevated above the base flood elevation for mitigation of coastal and inland flooding. This is typically accomplished through placing additional beam and pier supports under a raised slab home. In this process, the slab support conditions are changed from uniform soil support to beam supports. This may lead to unanticipated stress/strain changes, concrete cracks and slab failure. This paper presents a numerical parametric study of such elevated slabs with non-linear finite element approach. The models were calibrated with data obtained from full-scale testing of two concrete slabs under uniform floor load, one of which was retrofitted with external carbon fiber reinforced polymer (CFRP) laminates at critical locations. The slabs were supported by typical wide-flange steel beams over hollow square concrete block masonry piers. The results showed that typical elevated slabs can behave in a brittle manner with low ductility and sudden explosive collapse. A single layer of a uniaxial CFRP application at the negative moment locations increased the floor load capacity by about 30% and more than three times the minimum building code specified live load. Increased beam spacing and lower slab thickness decreased the slab load capacity, as expected.

Adequately reflecting the severity of tropical cyclones using the new Tropical Cyclone Severity Scale

For decades, meteorologists and governments have been warning communities in coastal areas for an imminent tropical cyclone (TC) using the Saffir-Simpson Hurricane Wind Scale (SSHWS). The SSHWS categorizes a TC based on its maximum wind speed, and is used in defining evacuation strategies and humanitarian response. However, the SSHWS considers only the wind hazard of a TC, whereas a TC can also cause severe conditions through its high storm surges and extreme rainfall, triggering coastal and inland flooding. Consequently, the SSHWS fails to mirror the TC’s total severity. This becomes evident when looking at past events such as Hurricane Harvey (2017), which was classified as a Tropical Storm while it caused widespread flooding in the Houston (TX) area, with precipitation totals exceeding 1.5 m. Without including storm surge and rainfall information, adequate risk communication with the SSHWS can be challenging, as the public can (mistakenly) perceive a low-category TC as a low-risk TC. To overcome this, we propose the new Tropical Cyclone Severity Scale (TCSS) that includes all three major TC hazards in its classification. The new scale preserves the categorization as used in the SSHWS, to maintain familiarity amongst the general public. In addition, we extend the scale with a Category 6, to support communication about the most extreme TCs with multiple hazards. The TCSS is designed to be applied on a local-scale, hereby supporting local-scale risk communication efforts and evacuation strategies prior to a TC landfall. The scale can be used for risk communication on both the total TC risk and on the categories of the separate hazards, which can be valuable especially in cases when one hazard is the predominant risk factor, such as excess rainfall triggering flooding.

Perceptions of nature-based solutions for Urban Water challenges: Insights from Australian researchers and practitioners

Nature-Based Solutions (NBS) have recently gained traction as integrated approaches that can address societal challenges by simultaneously providing human well-being and biodiversity benefits. Among the benefits of NBS, their capacity to address urban water challenges – such as inland and coastal flooding –while providing ecological benefits has been a recent area of focus globally. While interventions that are labelled ‘Nature-Based Solutions’ have been widely integrated into policy and practice in Europe, the term has not been extensively adopted in Australian policy and praxis. This research examines how Australian water professionals from research and practice understand, conceptualise and use the concept, ‘Nature-Based Solutions’ (NBS) in addressing urban water challenges. We interviewed 27 water professionals in research and practice with diverse disciplinary backgrounds across four Australian states and asked them to provide their definition of NBS. The results show that alternative terminologies such as Green Infrastructure and Water Sensitive Urban Design are predominantly used. We present the participants’ perspectives on the adoption of this term in Australia, and discuss the value and contributions of NBS as an umbrella concept. We conclude by providing insights on the potentials and limitations of the term, and propose ways to move beyond a focus on terminology and definitions towards facilitating the uptake and implementation of NBS in our cities.

Numerical Comparisons of Flow Properties Between Indivisual and Comprehensive Consideration of River Inundation and Inland Flooding

Numerical Comparisons of Flow Properties Between Indivisual and Comprehensive Consideration of River Inundation and Inland Flooding

Rivers in the sky, flooding on the ground: the role of atmospheric rivers in inland flooding in central Europe

Abstract. The role of large-scale atmospheric circulation and atmospheric rivers (ARs) in producing extreme flooding and heavy rainfall events in the lower part of the Rhine catchment area is examined in this study. Analysis of the largest 10 floods in the lower Rhine, between 1817 and 2015, shows that all these extreme flood peaks have been preceded up to 7 d in advance by intense moisture transport from the tropical North Atlantic basin in the form of narrow bands also known as atmospheric rivers. Most of the ARs associated with these flood events are embedded in the trailing fronts of the extratropical cyclones. The typical large-scale atmospheric circulation leading to heavy rainfall and flooding in the lower Rhine is characterized by a low pressure center south of Greenland, which migrates toward Europe, and a stable high pressure center over the northern part of Africa and the southern part of Europe and projects on the positive phase of the North Atlantic Oscillation. On the days preceding the flood peaks, lower (upper) level convergence (divergence) is observed over the analyzed region, which indicates strong vertical motions and heavy rainfall. Vertically integrated water vapor transport (IVT) exceeds 600 kg m−1 s−1 for the largest floods, marking these as very strong ARs. The results presented in this study offer new insights regarding the importance of moisture transport as a driver of extreme flooding in the lower part of the Rhine catchment area, and we show, for the first time, that ARs are a useful tool for the identification of potentially damaging floods in inland Europe.

Constructing Hurricane Florence’s Flooding: Comparing Local and National News

ABSTRACT This study examines local and national news coverage of hurricane-related flooding, including storm surge and coastal flooding during the weather event and subsequent inland flooding. Understanding the nature of media messaging regarding flooding related to hurricanes is crucial to not only identifying implications for broader social dynamics in an age of accelerating climate change, but also to provide insight for local and national journalists tasked with covering hurricanes. Using the case study of coverage of Hurricane Florence, this analysis assesses how hurricane news coverage may be potentially motivating or demotivating audiences to pursue behaviors such as preparing for hurricanes, evacuating if need be, helping neighbors with fewer resources, and aiding in recovery efforts. We find that news constructions did vary between local and national coverage in terms of threat and efficacy messaging and flood frames, and these changed over time. Findings are discussed in terms of implications for covering hurricanes in an age of accelerating climate change.

Objective approach for rainstorm based on dual-factor feature extraction and generalized regression neural network

Rainstorm often causes inland flooding and mudslides that threaten lives and properties. In this study, rainstorm is used as a forecasting object, and an interpretation prediction model for rainstorm based on the European Center for medium-range weather forecasting (ECMWF) numerical prediction model is constructed through the generalized regression neural network method. Model inputs are forecasted through principal component analysis, and dual-factor feature extraction is performed on the primary predictors to obtain new irrelevant variables and optimize network structures. The experimental forecast results of the 24 h aging test using an independent sample of large-scale rainstorm in Guangxi, China from 2012 to 2016, the actual forecast results of selected rainstorm cases with great influence on Guangxi, and different influencing systems show that the new prediction scheme is sophisticated. Thus, the scheme has a certain universal applicability. The results of the comparative analysis between the new program and ECMWF show that the forecasting ability of the new method is more accurate than that of the direct numerical forecasting model. The threat score of the new forecast model for 5 years has a 58.4% increase relative to that of the ECMWF. The forecasting skills are positive and good and can thus improve the rainstorm forecasting ability of ECMWF and provide a better guidance for forecasters.

Performance evaluation of potential inland flood management options through a three-way linked hydrodynamic modelling framework for a coastal urban watershed

Abstract This study proposes a novel comprehensive hydrodynamic flood modelling framework over Mithi river watershed in Mumbai, India, a coastal urban area, to reduce the inundation extent by incorporation of different inland hydraulic scenarios. First, the study addresses the issue of data scarcity by adapting alternate robust techniques to estimate design rainfall, tidal elevation and discharge, the key inputs for a flood model. Following that, a three-way linked flood model has been developed in the MIKE FLOOD platform, considering river, stormwater, overland flow and tidal influence to generate flood inundation and subsequently hazard maps for various inland hydraulic scenarios, by incorporating different feasible cross-sections and lining materials. The flood inundation and hazard maps have been derived for 10-, 50- and 200-year return periods of design rainfall, discharge and tide to identify the best possible flood-reducing hydraulic scenario. It is observed that a ‘trapezoidal river cross-section lined with concrete’ relatively maximizes the reduction in flooding extent. The proposed framework can be implemented as an effective flood mitigation strategy in data-scarce, densely populated and space-constrained areas.

A Proposed Simultaneous Calculation Method for Flood by River Water, Inland Flood, and Storm Surge at Tidal Rivers of Metropolitan Cities: A Case Study of Katabira River in Japan

All metropolitan cities in Japan are located in low-lying areas that surround ports. Accordingly, significant floods that occur in these cities will trigger the simultaneous occurrence of flooding by river water and inland flooding. However, existing studies have focused on the impact of flooding by river water, inland flooding, and high tide in tidal rivers, and disaster mitigation measures focused on detailed flooding processes in such flooding areas have not been conducted thus far. This study focused on a tidal river, i.e., Katabira River of Yokohama city, one of Japan’s metropolitan cities, to construct a simultaneous occurrence model of flooding by river water and inland flooding, including the impact of a high tide. Numerical analysis was conducted using this model, and the results show that the flooded area significantly changed from 0.004 to 0.149 km2 according to the tide level of the estuary. Moreover, by simultaneously solving the calculation of flooding by river water and inland flooding, we found that there was a difference of 50 min between the occurrences of these floods. Therefore, we found that there is a possibility that, if evacuation is not conducted at the time of occurrence of inland flooding, evacuation during subsequent river-water flooding may not be possible. Based on these results, our proposed method was found to be useful for tidal rivers of metropolitan cities.

Rohingya refugee flooding and changes of the physical and social landscape in Ukhiya, Bangladesh

Bangladesh has been dealing with one of the world’s largest refugee emergencies along its border with Myanmar (especially in the rough wooded zone of Ukhiya sub-district, Cox’s Bazar) due to a massive influx of Rohingya refugees, particularly since 25 August 2017. Resulting high impacts threaten the viability of local plantation as well as natural forests (societal and ecological assets). This research aims to evaluate the impact of the influx on the physical landscape in the Ukhiya sub-district as well as changes of socio-cultural landscape. The study was relied on both geo-spatial and survey data analysis. We argue that Rohingya flooding has a significant impact on changes of physical and socio-cultural landscape of the area in and around Rohingya camps. Results from the normalized difference vegetation index analysis identified that during 2015–2018 the forestry adjacent to the Kutupalong camps (Ukhiya sub-district) declined by 11.23 km2. Forestry cover fell from approximately 68.9% of all land to 2.72%; the decline representing about 15.2% of the entire forested area. Furthermore, the highest elevated area of Kutupalong camps (estimated to be 41 m) is likewise affected by anthropogenic activities, for instance, wholesale cutting into the slope, and street and stair construction which is gradually rising the potentiality of landslide and inland flood in several camps. Out of which 27.76% settlements, 0.35% and 9.61% settlements are at risk of landslide and flood, respectively, in the Kutupalong RC and Kutupalong extension campsite. A large proportion of Rohingyas also used wood for fuel; wood used originates from the adjacent forest and is the primary explanation for forestry consumption in Ukhiya sub-district. Its forests and elevation will never return to their original condition if the consumption of forestry assets proceeds unabated. It is argued, that these research findings may inspire locals, national, and global aid agencies to contribute to the introduction of forestry management and environmental protection.

Groundwater Regulation and the Development of Alternative Source Waters to Prevent Subsidence, Houston Region, Texas, USA

Abstract. Since the development of the coastal areas near present-day Houston, Texas, USA, subsidence has been a significant public policy concern. Subsidence in this area is caused by the extraction of groundwater from the Coastal Lowlands aquifer system, locally referred to as the Gulf Coast Aquifer. Concerns associated with subsidence in the Houston area include coastal inundation from storm surge, inland flooding, and critical infrastructure damage. The Houston area receives about 126 cm of precipitation each year, making flooding a critical issue in the region. The Houston area is the 4th largest city in the United States with a population of about 6.89 million (2017) and has a total water demand of about 4 Mm3 per day (2017). In the 1950s the City of Houston began the development of several reservoirs to provide water for the rapidly growing city. In 1975, following decades of subsidence totaling over 3 m, the Harris-Galveston Subsidence District (District) began regulating the use of groundwater and shifting the primary water supply for the region from groundwater to treated surface water to cease on-going and prevent future subsidence. Leveraging the alternative resources developed by the City of Houston in the 1950s, the District's regulatory framework focuses on spatial prioritization and the systematic conversion to alternative source waters. The District's regulatory plan includes three planning areas. Currently, the regional water authorities and the City of Houston are developing nearly five billion dollars (USD) in infrastructure to produce and deliver an additional 1.2 Mm3 per day of treated surface water to Houston and the surrounding communities. Resource development, public engagement, and political foresight have resulted in a reasonable approach to shift source waters and implement a plan to dramatically reduce and stop subsidence in the region. Figure 2 presents subsidence rates (2017) by regulatory area. Results show that the implementation of the regulatory program has substantially slowed subsidence in Areas 1 and 2, where full conversion has taken place. Planning the future water needs of the Houston area resulted in a robust and effective collaboration between the regulated community and the District. Analysis of historical source water use, aquifer response, and subsidence in the Houston area shows that the reasonable management of groundwater use in the Houston region is vital for the long-term prevention of subsidence and increases the resilience of the entire region.

Using Resilience in Risk-Based Asset Management Plans

Each state in the U.S.A. is required to develop and maintain a risk-based transportation asset management plan for the National Highway System (NHS) to improve or preserve the condition of the assets and the performance of the system. Awareness of natural hazards and extreme weather events has also increased with recent catastrophic hurricanes, such as Matthew (October, 2016) and Harvey (August, 2017), which caused significant inland floods in Robeson County, North Carolina, and Houston, Texas, respectively. These recent events and the damage to transportation infrastructure has also focused attention on the resilience of transportation networks. However, an integrated, consistent, well-understood method to assess or quantify the resilience of transportation networks is still lacking. This paper reviews the relevant concepts, legislative requirements that link asset management, risk and resilience, and tools available to support risk-based asset management. Based on a review of the transportation asset management plans developed by 49 state departments of transportation in 2018 and 2019, the paper summarizes the approaches to the risk management section of these asset management plans and the role resilience plays. Opportunities to better integrate resilience into the risk-based asset management plans are then identified. Examples are presented that demonstrate the role of resilience-related technical performance measures that reflect decisions related to flooding in the various stages of the disaster cycle (preparedness, response, recovery, and mitigation).

Coupled Hydrodynamic and Geospatial Model for Assessing Resiliency of Coastal Structures under Extreme Storm Scenarios

The hydrodynamic effects of flooding during extreme storm events are the leading cause of structural damage to impacted properties and due to their complexity, it is difficult to accurately estimate structural damage and flood vulnerability. We propose a robust structural damage assessment model that considers the dynamic behavior of flooding coupled with the structural and regional characteristics of buildings by using of a pair hydrodynamic model i.e., the advanced circulation (ADCIRC) and two-dimensional unsteady flow (TUFLOW). Fine-scale inland flooding scenarios were developed to simulate heavily impacted areas of coastal New Jersey in the United States (US) based on the historical storm Hurricane Sandy (2012). The models were calibrated and validated using multiple sets of observed data as well as using several performance metrics. The corresponding Nash–Sutcliffe efficiency (NSE) and R-squared (R2) values were found to be in the range of 0.426–0.81 and 0.56–0.91, respectively, during the ADCIRC calibration process. A spatial comparison with the observed inundation data revealed that the correlation coefficient and root mean square error (RMSE) for the inland flood modelling by TUFLOW were 0.79 and 0.71, respectively, with a 96.49% coefficient of similarity. A structural damage model was developed by combining the hydrodynamic components of flooding with several structural characteristics. In a comparison of the observed and model-simulated damage counts, the results indicate the conservative nature of the damage-prediction model with a mean absolute error (MAE) of 40.26 and RMSE of 58.67. Using a GIS framework, the damage assessment results for a particular type of storm were mapped to illustrate the damage levels of individual properties.