Comparative analysis between different flood assessment technologies in HAZUS-MH

Natural disasters devastate the United States through both economic loss and loss of life. The world wide economic damage that results from natural disasters has more than tripled in the last thirty years. Of these natural disasters, floods are the most chronic and costly disasters, comprising an average $5 billion dollars of damage each year. FEMA has released a new software program called HAZUS-MH, which attempts to capture economic losses caused by flooding before losses occur and predict losses from real-time events. This estimate is accomplished through the coupling of flood hazard modeling with local data. FEMA’s goal is that the information constructed within the program will help planners to mitigate and capture flood related losses. This study provides a methodology for assessing the accuracy of HAZUS level one flood loss estimates by examining the extent to which HAZUS default building stock inventory data represents the built local environment. The study area is concentrated in the northwest corner of Livingston Parish, Louisiana. The area is comprised of 200 census blocks that were chosen due to their proximity to the Amite River. Thus it is an area prone to floods. Livingston Parish is located in the Mississippi River and Lake Maurepas Basin, which collectively cover approximately 236,000 acres. 70% of the Parish’s land is located within FEMA’s 100-year flood plain. Building count for structures was obtained using remote sensing technology, processed and used to populate HAZUS ® MH default databases. Flood loss estimations were run for all of the data sets and results were compared for a significant difference. Differences in flood loss between the two analyses were found in isolated areas. This demonstrated the need to incorporate growth and development information into flood loss estimation methodologies

Flash Flood Susceptibility Evaluation in Human-Affected Areas Using Geomorphological Methods—The Case of 9 August 2020, Euboea, Greece. A GIS-Based Approach.

Flash floods occur almost exclusively in small basins, and they are common in small Mediterranean catchments. They pose one of the most common natural disasters, as well as one of the most devastating. Such was the case of the recent flood in Euboea island, in Greece, in August 2020. A field survey was accomplished after the 2020 flash floods in order to record the main impacts of the event and identify the geomorphological and man-made causes. The flash flood susceptibility in the urbanized alluvial fans was further assessed using a Geographic Information System (GIS)-based approach. Our findings suggest that a large portion of the alluvial fans of Politika, Poros and Mantania streams are mainly characterized by high and very high hazard. In fact, ~27% of the alluvial fans of Politika and Poros streams are characterized with very high susceptibility, and ~54% of Psachna area. GIS results have been confirmed by field observations after the 2020 flash flood, with significant damages noted, such as debris flows and infrastructure damages, in buildings, bridges and the road networks. In addition, even though the adopted approach may be more time-consuming in comparison to purely computational methods, it has the potential of being more accurate as it combines field observations and the effect of past flooding events

Utilization, planning, and problem evaluations of urban arterial waterways and corridors as an urban resource.

Widespread concern about flooding and possible use of the nation's urban river corridors has generated unprecedented interest in the potential for utilization of urban riverine corridors while simultaneously protecting the environment. This research effort is directed toward the development of a conceptualized plan to utilize the arterial waterways and intermittent streams as a resource and an asset to the community, so that existing problem areas can be economically transferred into useful and feasible activity centers. Flooding problems and methods of flood mitigation, both structural and non-structural are presented. Physical effects of certain practices, such as sand mining and its effect upon flooding, sedimentation, river regime changes, erosion and backwater are also presented. A river corridor plan is invoked on the basis of a study of the soil, topography, vegetation, hydrology and cultural features assembled and an array of potential benefits from reclaiming the corridors presented. A multi-purpose, multiple-approach river corridor plan strategy has been developed and general application to riverine corridor areas has been made

Spatial prediction of flood susceptible areas using machine learning approach: a focus on west african region

Dissertation submitted in partial fulfilment of the requirements for the Degree of Master of Science in Geospatial TechnologiesThe constant change in the environment due to increasing urbanization and climate change has led to recurrent flood occurrences with a devastating impact on lives and properties. Therefore, it is essential to identify the factors that drive flood occurrences, and flood locations prone to flooding which can be achieved through the performance of Flood Susceptibility Modelling (FSM) utilizing stand-alone and hybrid machine learning models to attain accurate and sustainable results which can instigate mitigation measures and flood risk control. In this research, novel hybridizations of Index of Entropy (IOE) with Decision Tree (DT), Support Vector Machine (SVM), Random Forest (RF) was performed and equally as stand-alone models in Flood Susceptibility Modelling (FSM) and results of each model compared. First, feature selection and multi-collinearity analysis were performed to identify the predictive ability and the inter-relationship among the factors. Subsequently, IOE was performed as bivariate and multivariate statistical analysis to assess the correlation among the flood influencing factor’s classes with flooding and the overall influence (weight) of each factor on flooding. Subsequently, the weight generated was used in training the machine learning models. The performance of the proposed models was assessed using the popular Area Under Curve (AUC) and statistical metrics. Percentagewise, results attained reveals that DT-IOE hybrid model had the highest prediction accuracy of 87.1% while the DT had the lowest prediction performance of 77.0%. Among the other models, the result attained highlight that the proposed hybrid of machine learning and statistical models had a higher performance than the stand-alone models which reflect the detailed assessment performed by the hybrid models. The final susceptibility maps derived revealed that about 21% of the study area are highly prone to flooding and it is revealed that human-induced factors do have a huge influence on flooding in the region

Comparative assessment of the vulnerability and resilience of 10 deltas : work document

Background information about: Nile delta (Egypt), Incomati delta (Mozambique), Ganges-Brahmaputra-Meghna (Bangladesh), Yangtze (China), Ciliwung (Indonesia), Mekong (Vietnam), Rhine-Meuse (The Netherlands), Danube (Romania), California Bay-Delta, Mississippi River Delta (USA

Distributed River Basin Modeling for Analyzing Flood Mitigation Measures under Non-stationary Conditions

Flood frequency analysis is in the main component of flood risk management projects, influencing pre and post-flood activities. Apart from its importance and the intense research in the area, the available hydrological methods are not adequate, especially under non-stationary conitions caused by land cover or climate change. In this work a new hydrological model is proposed, with the goal of overcome the main weakness of the traditional methodologies. This research is composed by three main goals. First, the authors attend to add functionalities to an existing calibration-free hydrological model based on the scaling theory of floods. The goal is to provide a better representation of the rainfall-runoff processes that occur in a hillslope scale through the use of empirical models. This model constitutes an important tool for the evaluation of effects of land characteristic changes on flood intensity and frequency. The second goal is the development of a flood risk framework, with the aim of link hydrological criteria of flood intensity estimation (peak discharge) to criteria that measures flood impact (damages). This activity requires the development of flood maps and the quantification of flood damage. This research presents a simplified methodology for flood risk mapping that can be used for areas with very limited information about the river network. Annual expected damage was used as criteria to evaluate different land characteristics scenarios, being damage estimated by a simple model based on the city parcels structure value and water level-damage curves proposed by FEMA. The last goal is to develop a simplified case study to demonstrate the model applicability on flood risk management. A case study for Charlotte City, North Carolina was developed. The city has experienced an extensive urban growth since 1960 which has led to significant changes in city's risk and vulnerability to floods. The impacts of urbanization were evaluated using current land cover conditions and two extreme scenarios: pre-development and built-out. The effectiveness of non-punctual flood mitigation measures that are easily harmonized in the urban environment was also evaluated. The innovative aspect of this study is to present a new methodology for flood frequency analysis that does not require calibration and has the potential to be applied to any region in the world. By this framework a multiple scale analysis of flood peak and flood damage is obtained, prviding essential information for the implementation of an optimal flood risk management policy over different levels of governmental policies (local, regional and global)

Comparitive assessment of the vulnerability and resilience of 10 deltas, synthesis report

The proposed framework for delta assessment and especially the scorecards are intended to enhance awareness raising, discussion and prioritization on most relevant delta issues, in each delta but also in comparison with other deltas. This should lead to more efficient and effective (multi-sectoral) policy formulation, management design and implementation, in concrete Delta plans, pilot-projects and (research) programmes. The target groups are all stakeholders who are involved in delta management at different levels and with different interests (government, private companies, NGOs, public), and who wish to contribute to the resilience of their own delta and other deltas worldwide

Five feet high and rising : cities and flooding in the 21st century

Urban flooding is an increasingly important issue. Disaster statistics appear to show flood events are becoming more frequent, with medium-scale events increasing fastest. The impact of flooding is driven by a combination of natural and human-induced factors. As recent flood events in Pakistan, Brazil, Sri Lanka and Australia show, floods can occur in widespread locations and can sometimes overwhelm even the best prepared countries and cities. There are known and tested measures for urban flood risk management, typically classified as structural or engineered measures, and non-structural, management techniques. A combination of measures to form an integrated management approach is most likely to be successful in reducing flood risk. In the short term and for developing countries in particular, the factors affecting exposure and vulnerability are increasing at the fastest rate as urbanization puts more people and more assets at risk. In the longer term, however, climate scenarios are likely to be one of the most important drivers of future changes in flood risk. Due to the large uncertainties in projections of climate change, adaptation to the changing risk needs to be flexible to a wide range of future scenarios and to be able to cope with potentially large changes in sea level, rainfall intensity and snowmelt. Climate uncertainty and budgetary, institutional and practical constraints are likely to lead to a combining of structural and non-structural measures for urban flood risk management, and arguably, to a move away from what is sometimes an over-reliance on hard-engineered defenses and toward more adaptable and incremental non-structural solutions.Hazard Risk Management,Wetlands,Natural Disasters,Adaptation to Climate Change,Climate Change Impacts

Developing a Biophilic City through Natural Land Transformation Analysis and Geodesign: The case of Purbachal New Town, Bangladesh

Dhaka, the capital city of Bangladesh is one of the fastest-growing metropolitan regions in the world. To solve the ever-increasing need for housing and to reduce the pressure of the population from the capital city, the Purbachal satellite city was planned. It is the biggest planned township in Bangladesh with an area of over 25 square kilometers. Purbachal is situated at the confluence of the Shitalakhya and Balu rivers. Historically a low-lying wetland, Purbachal has gone through a rapid transformation in past decades. The water bodies around the area have been filled in to create new developable land. Through remote sensing and GIS analysis, this study investigates the transformation of wetland areas in Purbachal New Town. The study Investigates whether the new developments in the Purbachal New Town followed a natural topography or it was drastically modified from its natural conditions. The study also investigates how these changes in the inherent topographical nature of the area can influence the future of the city. The goal of the study is to explore the complex interrelation of different factors responsible for the growth of a city. The main aim is to formulate a realistic city planning process to synthesize systems city approach with the concept of Biophilic design to create spaces where people will be able to live in harmony with nature

Heavy rains triggering flash floods in urban environment: A case from Chiavari (Genoa metropolitan area, Italy)

Between 10th and 11th November, 2014, heavy rainfall over a short period fell on the eastern Genoa metropolitan area. The geohydrological event had important ground effects, among them the simultaneous flooding of Entella and Rupinaro streams, in Chiavari city. In lower Lavagna valley, the main tributary of the Entella, a landslide caused two casualties, while serious damage to buildings and infrastructures were registered in Chiavari\u2019s Old Town and in the nearby communities of Carasco and Cogorno. In the Entella basin, the rainfall peaked at 60 mm/hour and accumulated 220 mm in six hours. The levels of the streams rose instantly, showing concentration times of less than an hour. The Entella rose seven meters, flooding Carasco, Cogorno, and the Caperana neighborhood of Chiavari. Flash flooding of the Rupinaro stream caused water to rise to 1.5 m in Chiavari\u2019s historic core. Analyses were carried out of the weather conditions and the ground effects of the events; in addition, studies were made of the main causes of the geo-hydrological risk. In particular, variations in climate and uncontrolled urban development were the cause of increased geo-hydrological hazards and vulnerability of this area, historically subject to flooding. Such conditions of risk are unacceptable, and urgent measures are required to mitigate the effects of heavy rainfall events