High Flood Risk Research Articles

Flood Risk Assessment of Communities to Flood Hazards in Central Niger Delta, Nigeria

The study examined the risk assessment of communities in the Central Niger Delta, Nigeria with a view to employing analytical hierarchical ranking process technique. The study considered the landuse, elevation, soil texture and proximity to active river channels as factors determining flood vulnerability (FV) while factors such as accessibility, social infrastructure, water supply, agriculture, commercial activities and disaster preparedness of communities were used for flood exposure (FE) using purposive sampling technique. Both FV and FE were combined together using UNION Module of ArcGIS 10.5 to produce flood risk map of the Central Niger Delta. Descriptive statistics using frequency and percentages were used for the data analysis. Findings revealed that 20.25%, 51.66% and 28.09% of the entire study area were lowly vulnerable, moderately vulnerable and highly vulnerable to flood. Similarly, 0.3%, 45.7% and 54.8% were lowly exposed, moderately exposed and highly exposed to flood. However, 14.3%, 28.3% and 57.4% of the study area had low flood risk, moderate flood risk and high flood risk respectively. The study concluded that majority of the area in the Central Niger Delta is risky to flood. It is recommended among others that channelization and dredging of River Niger Creeks in the study area are important in order for the river to accommodate more volume of water whenever there is excessive rainfall.

Experiencing, caring, coping: Vested interest mediates the effect of past experience on coping behaviors in environmental risk contexts

AbstractSocial psychology provides a treasure‐trove of insights into adaptations that may limit the devastating effects of climate change. Vested Interest Theory may contribute to this knowledge base, suggesting that one's vested interest may significantly influence appropriate coping behaviors, as it is has been shown to enhance the relation between attitudes and self‐relevant behaviors. The theory's utility is investigated in an environmental risk context. Here, we replicate previous research findings showing that citizens in high‐risk areas perceived higher risk and stronger intentions to cope with it when vested interest perceptions were salient. Furthermore, the current studies investigate the behavioral effect of vested interest on coping with an environmental risk (flooding): results showed that vested interest significantly mediated the past experience–coping behaviors relationship. In Study 1’s mediation analysis (Rome and Vibo Valentia, Italy, N = 466), past experience of flood risk enhanced vested interest in flood risk, which in turn increased volunteering for flood prevention activities, thereby mitigating risk. In Study 2 (N = 391), the same mediation effect was replicated in the Timis region, a high flood risk area in western Romania. These results shed light on literature inconsistencies on this topic, providing insights for the theoretical understanding of the relationship between past experience of a given risk and related coping behaviors, possibly shedding light to the risk perception paradox. These insights may drive effective intervention strategies to enhance people's behavioral coping with environmental risks.

Comparing the Effects of Different Daily and Sub-Daily Downscaling Approaches on the Response of Urban Stormwater Collection Systems

Change in the spatiotemporal pattern of precipitation is one the most important effects of climate change. This may result in considerable changes in urban flooding and yield a variation in the rate and volume of stormwater, resulting in the failure of stormwater collection systems. In the current paper, the effects of different downscaling methods on a built urban network have been assessed and compared. The case study is a 320-ha urban watershed with a built stormwater collection system located in the City of Tehran, Iran. Two single (SDSM and DMDM) and two multisite downscaling techniques with a daily temporal resolution have been employed and two sub daily (based of GEV distribution and MOF) methods have been used to further disaggregate the downscaled data. To evaluate the climate change impacts, three climate change scenarios, i.e. RCP 2.6, RCP 4.5 and RCP 8.5, have been used. Based on our findings, DMDM appears to outperform the other techniques in terms of our statistical similarity and dissimilarity metrics for daily downscaling. In addition, the sub-daily disaggregation method via GEV distribution delivers better results in comparison to the MOF. After simulating the stormwater collection system based on the downscaling results, we found that the number of flooded channels and junctions using RCP 8.5 results is significantly higher than RCP 4.5 and RCP 2.6 scenarios, indicating the relatively high risk of urban flooding under RCP 8.5 scenario.

Financial Relations in Flood Insurance: US Experience, use in Russia

A flood is a natural disaster that threatens the economy through the damage caused. Establishing an effective financial mechanism for assessing damage and providing flood insurance is becoming increasingly important. An analysis of the financial relationships between government and insurance organizations in the field of US insurance, related directly to the management system in flood-prone areas, allows us to develop recommendations for building an effective flood insurance system in Russia. Research into the costing of the US national flood insurance program and the appropriate level of subsidies for existing properties in high-risk flood areas is part of the scientific study of the interaction between insurance and government funding. The article provides an overview of the mechanism for the distribution of financial resources in areas prone to flooding. Proposals are presented regarding the creation of an effective flood insurance system in Russia, which will ensure the coordination of actions of various levels of government, scientifically grounded zoning in flooded areas, as well as the establishment of compulsory insurance of social, housing, and communal facilities in flood-prone areas.

Homes and Other Buildings Abound in Natural Hazard Hot Spots

Researchers mined maps of natural hazards and land use to show that nearly 60% of structures are built in regions at high risk of earthquakes, wildfires, floods, hurricanes, and/or tornadoes.

Multi-Criteria Evaluation (MCE) Method for the Management of Woodland Plantations in Floodplain Areas

The potential of woodland and floodplain woodland plantations in a wide area, of high flood risk, along the Spey River (Scotland) is investigated, to mitigate the floods’ catastrophic impact. The spatial analysis required various datasets to be overlaid, to define the suitable sites for woodland and floodplain woodland establishment. These datasets that concern the topography, the physical and technical characteristics (existing woodland, road system, urban and rural areas, river system and open water areas, railway) and the protected sites of the study area were obtained and merged using Geographical Information System (GIS) techniques. The most suitable and unsuitable areas within the region were identified, using multi-criteria evaluation methods (Boolean approach). In total, 13 constraints were created by expressing true/false statements for each factor, and were combined together using spatial analysis tools. The results revealed the high potential of woodland and floodplain woodland plantations to prevent floods, with 59.2% of the total study area (177.5 km2) determined to be appropriate for such practices’ application. The River Dulnain tributary demonstrated the highest potential for floodplain woodland planting, followed by Rivers Avon and Fiddich, and the southwestern and northeastern Spey River parts. The methodology proposed is simple and provides rapid and accurate results at low cost, while the datasets can be easily accessed and are available in convenient type/format. This useful methodology for researchers and authorities could be applied successfully to similar watersheds, contributing significantly to flood risk mitigation and the enhancement of the flood-preventative measures’ planning efficiency.

Analyzing the spatiotemporal dynamics of flood risk and its driving factors in a coastal watershed of southeastern China

Rapid urbanization and climate change can cause more extensive flood risk, in the absence of urgent and efficient adaptation measures. As the occurrence of floods varies with time and space, comprehensive and dynamical assessment of the spatiotemporal variability of flood risk and understanding of its drivers is vital for flood risk management. In this study, we developed a spatial multi-criteria analysis (SMCA) framework for quantifying the spatiotemporal dynamics of flood risk through a case study in a coastal watershed of southeastern China from 1990 to 2015. A comprehensive framework for flood risk assessment was constructed from the hazard, exposure, sensitivity and adaptive capacity components with 23 indicators. The results showed that the highest risk happened in the stage of 2006–2010, while the lowest risk stage was 2011–2015, with higher flood risk in the downstream areas of Jiulong River watershed (JRW). The contribution of each indicator reflects the difference in temporal, spatial and quantity aspects. The top 5 driving factors for JRW included: peak discharge, maximum daily rainfall, age structure, wetland, and reservoir. The risk perception showed a continuous growing impact on flood risk. However, some indicators only showed obvious contributions in the specified area: for example, the built-up expansion in Zhangzhou city; the increase of dike length and the improvement of dike standard in Xinluo district; and the increase of government financial investment in Zhangping and Liancheng district. This study demonstrates the well-performance of our proposed novel approach for flood risk assessment. Our results and conclusions are also of significance for policymakers to understand and point out the deficiencies in the current actions of flood adaption, and consequently develop more targeted and spatially-specific strategies for flood adaptation, in the context of climate change and rapid urbanization.

Flood risk awareness and property values: evidences from Seoul, South Korea

ABSTRACT There is ongoing debate about flood risk discounts regarding property values. While some researchers claim that housing prices reflect flood risk, a growing body of literature has shown that flood risk is quickly forgotten after a flood event, and risk discounts are minimal in the long term. This study provides new evidence of flood risk discounts, with an emphasis on the role of flood risk awareness based on the case of Seoul, South Korea. This paper empirically examines how flood risk discounts vary depending on past flood experiences, and analyzes whether they are affected by the disclosure of inundation hazard maps. According to the results, flood risk discounts are disproportionally higher in districts with severe past flood experiences, but interestingly, there is no evidence that negative disclosure effects of hazard information on property values exist. These findings imply that home buyers carefully consider flood risk in their housing transactions in high flood risk areas, even before hazard maps become available, possibly because having flood insurance is rare in South Korea. Understanding the relationship between flood risk awareness and risk discounts in terms of property values has vital implications for disaster management policies as they relate to cities’ resilience. HIGHLIGHTS The flood risk discount in property values could be affected by the risk awareness. The risk discount is disproportionally high in areas with severe flooding experience. Negative disclosure effects of hazard map on property values do not exist in Seoul. Hazard disclosure could be actively used considering the level of the risk awareness.

An ice jam flood hazard assessment of a lowland river and its terminus inland delta

Flooding is one of the most frequent and most costly natural disasters that occur throughout Canada, and although there is ongoing work to update and improve flood hazard assessments and mapping of high flood risk rivers throughout the country, most studies only delve into open water flooding. However, many rivers in Canada experience higher peak water levels due to ice jamming, resulting in severe flooding of surrounding areas. Hence, there is an urgency to expand current flood hazard assessments to include ice jam flooding for better flood management practices. One area that is often plagued with ice jam flooding is the lowest reach of Manitoba’s Red River. The Lower Red River is a low-lying river with a terminus inland delta where water levels are governed by Lake Winnipeg. Ice jam floods often divert water into the lower Red River’s floodplain that is continually being encroached by development. RIVICE, Environment Canada’s one-dimensional ice hydraulic model, was set up within a Monte Carlo framework to simulate an envelope of backwater level profiles that result from ice jams within the study site. Non-exceedance probability profiles were created from the envelope of backwater level profiles to assess ice jam flood hazard.

Flash flood risk assessment using geospatial technology in Shewa Robit town, Ethiopia

Flash flood is an extreme flooding event which is quick, short-lived, hazardous phenomena having negative environmental and socio-economic impacts. Flood risk management is essential to reduce the effects of flood on human lives and livelihoods. The main goals of this research were flash flood risk analysis and risk quantification in terms of land use land cover using geo-spatial technology in Shewa Robit town. In the present study, elevation, slope, drainage density, distance from river, NDVI, land use land cover, topographic wetness index and curvature were used as parameters determining flash flood risk. To realize these research objectives, all these data were reclassified in to five classes and different weights for each of them was assigned using analytic hierarchy process. Weighted Sum Overlay (WSO) analyses of ARC GIS software was employed to produce flood vulnerability map. Then, the accuracy of generated flood risk map was validated using historical flood data. According to the result, about 3.08%, 14.62% and 20.66% of Shewa Robit town are at a very high, high and moderate flash flood risk, respectively. In addition to this, flood risk was also quantified in terms of land use land cover. The result indicates that the settlement land use is the most vulnerable with an estimated area of 12.01 ha, 99.57 ha and 174.16 ha in very high, high and moderate risk classes. The outcome of the study will be applicable in flood hazard management and mitigation strategies.

Flood risk mapping and crop-water loss modeling using water footprint analysis in agricultural watershed, northern Iran

Spatial information on flood risk and flood-related crop losses is important in flood mitigation and risk management in agricultural watersheds. In this study, loss of water bound in agricultural products following damage by flooding was calculated using water footprint and agricultural statistics, using the Talar watershed, northern Iran, as a case. The main conditioning factors on flood risk (flow accumulation, slope, land use, rainfall intensity, geology, and elevation) were rated and combined in GIS, and a flood risk map classified into five risk classes (very low to very high) was created. Using average crop yield per hectare, the amount of rice and wheat products under flood risk was calculated for the watershed. Finally, the spatial relationships between agricultural land uses (rice and wheat) and flood risk areas were evaluated using geographically weighted regression (GWR) in terms of local R2 at sub-watershed scale. The results showed that elevation was the most critical factor for flood risk. GWR results indicated that local R2 between rice farms and flood risk decreased gradually from north to south in the watershed, while no pattern was detected for wheat farms. Potential production of rice and wheat in very high flood risk zones was estimated to be 7972 and 18,860 tons, on an area of 822 ha and 7218 ha, respectively. Loss of these crops to flooding meant that approximately 34.04 and 12.10 million m3 water used for production of wheat and rice, respectively, were lost. These findings can help managers, policymakers, and watershed stakeholders achieve better crop management and flood damage reduction.

A stress test of urban system flooding upon extreme rainstorms in Hong Kong

Many cities face high flood risks due to intense rainstorms and dense urban environments. Quantifying the degree and duration of flood impact to urban systems under extreme rainstorms is essential for long-term flood risk management and short-term emergency response. This study aims to develop a novel stress testing framework for evaluating urban system flooding upon extreme rainstorms in Hong Kong. The stress testing framework is based on a pipe-surface coupled hydraulic model for detailed flood simulation in urban settings and a dynamic flood impact evaluation method for assessing interruptions to urban transportation and building systems. The proposed stress testing method is applied to assess the flood impacts in Kowloon, the most densely populated area in Hong Kong. Detailed urban settings such as engineering drainage facilities and buildings are incorporated into the flood simulation model, and the model is validated both qualitatively and quantitatively by field observations. Flood hazard scenarios are investigated under design rainstorms of different return periods (20, 100, and 1000 years), and the impacts on transportation and building systems are evaluated with the new process-based impact evaluation method. The results of the case study indicate that underground mass transit railway (MTR) stations and residential buildings will be more affected than highways and other types of buildings in Kowloon: up to 56% of MTR stations and 43% of residential buildings may be affected under the 1000-year rainstorm, with inundation durations of 8 and 7 h for the MTR stations and residential buildings, respectively. To ensure public transportation services and reduce potential exposure of residents during extreme rainstorms, mitigation measures should be taken to reduce the affected percentage and duration of MTR stations and residential buildings. The proposed methods contribute to enhanced societal flood preparedness, warning, and response.

Assessing the susceptibility of schools to flood events in Iran

Catastrophic floods cause deaths, injuries, and property damages in communities around the world. The losses can be worse among those who are more vulnerable to exposure and this can be enhanced by communities’ vulnerabilities. People in undeveloped and developing countries, like Iran, are more vulnerable and may be more exposed to flood hazards. In this study we investigate the vulnerabilities of 1622 schools to flood hazard in Chaharmahal and Bakhtiari Province, Iran. We used four machine learning models to produce flood susceptibility maps. The analytic hierarchy process method was enhanced with distance from schools to create a school-focused flood-risk map. The results indicate that 492 rural schools and 147 urban schools are in very high-risk locations. Furthermore, 54% of rural students and 8% of urban students study schools in locations of very high flood risk. The situation should be examined very closely and mitigating actions are urgently needed.

Urbanization and climate change impacts on future flood risk in the Pearl River Delta under shared socioeconomic pathways

Climate change and urbanization are converging to challenge the flood control in the Pearl River Delta (PRD) due to their adverse impacts on precipitation extremes and the urban areas environment. Previous studies have investigated temporal changes in flood risk with various single factor, few have considered the joint effects of climate change, urbanization and socio-economic development. Here, based on the representative concentration pathway (RCP) scenarios, we conducted a comprehensive assessment of future (2030–2050) flood risk over the PRD combined with a thorough investigation of climate change, urbanization and socio-economic development. Precipitation extremes were projected using the regional climate model RegCM4.6, and urbanization growth was projected based on the CA-Markov model. The economic and population development was estimated by the shared socio-economic pathways (SSPs). Flood risk mapping with different RCPs-urbanization-SSPs scenarios was developed for the PRD based on the set pair analyze theory. The results show that climate change and urbanization are expected to exacerbate flood risk in most parts of the PRD during the next few decades, concurrently with more intense extreme precipitation events. The high flood risk areas are projected mainly in the urban regions with unfavorable terrain and dense population. The highest flood risk areas are expected to increase by 8.72% and 19.80% under RCP4.5 and RCP8.5 scenarios, respectively. Reducing greenhouse gas emissions may effectively mitigate the flood risk over the PRD. This study highlight the links between flood risk and changing environment, suggesting that flood risk management and preventative actions should be included in regional adaptation strategies.

Toxicity travels in a changing climate

Climate change is imposing substantial consequences across physical and social infrastructures. The extent of social disruption and risk to human health are, however, potentially much broader than these general consequences, taken individually, would suggest. To address this gap, we assess the distribution of contaminated sites in the United States (US) and then estimate the impact that flood hazards in urban areas will have on these contaminated sites. Using these measures, we draw inferences about the risk of contamination from climate-impacted extreme weather events, climate adaptation at the local level, social risk and how it is distributed, and a broader understanding of the potential global consequences of climate change. In this paper we address three critical points: 1) the role classification of contaminated sites on our understanding of risk due to climate change; 2) the relationship between contaminated sites and flood risk; and 3) the potential for climate adaption strategies to mediate this risk. We estimate that of the roughly one-third of the US population living in urban areas, up to 3,338,518 people, are living in high-risk flood zones near contaminated sites. Our results suggest severe potential implications for estimates of the negative consequences from climate change and contamination and provide critical insights into the relationship between climate change and the built environment for urban planners and environmental policy makers and managers alike.

Assessing Property Level Economic Impacts of Climate in the US, New Insights and Evidence from a Comprehensive Flood Risk Assessment Tool

Hurricanes and flood-related events cause more direct economic damage than any other type of natural disaster. In the United States, that damage totals more than USD 1 trillion in damages since 1980. On average, direct flood losses have risen from USD 4 billion annually in the 1980s to roughly USD 17 billion annually from 2010 to 2018. Despite flooding’s tremendous economic impact on US properties and communities, current estimates of expected damages are lacking due to the fact that flood risk in many parts of the US is unidentified, underestimated, or available models associated with high quality assessment tools are proprietary. This study introduces an economic-focused Environmental Impact Assessment (EIA) approach that builds upon an our existing understanding of prior assessment methods by taking advantage of a newly available, climate adjusted, parcel-level flood risk assessment model (First Street Foundation, 2020a and 2020b) in order to quantify property level economic impacts today, and into the climate adjusted future, using the Intergovernmental Panel on Climate Change’s (IPCC) Representative Concentration Pathways (RCPs) and NASA’s Global Climate Model ensemble (CMIP5). This approach represents a first of its kind—a publicly available high precision flood risk assessment tool at the property level developed completely with open data sources and open methods. The economic impact assessment presented here has been carried out using residential buildings in New Jersey as a testbed; however, the environmental assessment tool on which it is based is a national scale property level flood assessment model at a 3 m resolution. As evidence of the reliability of the EIA tool, the 2020 estimated economic impact (USD 5481 annual expectation) was compared to actual average per claim-year NFIP payouts from flooding and found an average of USD 5540 over the life of the program (difference of less than USD 100). Additionally, the tool finds a 41.4% increase in average economic flood damage through the year 2050 when environmental change is included in the model.

How flood risks shape policies: flood exposure and risk perception in Swiss municipalities

Despite an increasing number of people exposed to flood risks in Europe, flood risk perception remains low and effective flood risk management policies are rarely implemented. It becomes increasingly important to understand how local governments can design effective flood risk management policies to address flood risks. In this article, we study whether high flood exposure and flood risk perception correlate with the demand for a specific design of flood risk management policies. We take the ideal case of Switzerland and analyze flood risk management portfolios in 18 flood-prone municipalities along the Aare River. We introduce a novel combination of risk analysis and public policy data: we analyze correlations between recorded flood exposure data and survey data on flood risk perception and policy preferences for selected flood risk management measures. Our results indicate that local governments with high flood risk perception tend to prefer non-structural measures, such as spatial planning and ecological river restoration, to infrastructure measures. In contrast, flood exposure is neither linked to flood risk perception nor to policy preferences. We conclude that flood risk perception is key: it can decisively affect local governments’ preferences to implement specific diversified policy portfolios including more preventive or integrated flood risk management measures. These findings imply that local governments in flood-prone areas should invest in raising their population’s awareness capacity of flood risks and keep it high during periods without flooding.

The Power of Nature‐Based Solutions: How Peatlands Can Help Us to Achieve Key EU Sustainability Objectives

AbstractPeatlands are lands with a peat layer at the surface, containing a large proportion of organic carbon. Such lands cover ≈1 000 000 km2 in Europe, which is almost 10% of the total surface area. In many countries, peatlands have been artificially drained over centuries, leading to not only enormous emissions of CO2 but also soil subsidence, mobilization of nutrients, higher flood risks, and loss of biodiversity. These problems can largely be solved by stopping drainage and rewetting the land. Wet peatlands do not release CO2, can potentially sequester carbon, help to improve water quality, provide habitat for rare and threatened biodiversity, and can still be used for production of biomass (“paludiculture”). Wisely adjusted land use on peatlands can substantially contribute to low‐emission goals and further benefits for farmers, the economy, society, and the environment.

Flood Risk Index for Land-Use Changes: Case Study of Pakpanang River Basin

Flood Risk Index (FRI) is the multi-criteria linked with the factors of vulnerability; exposure, susceptibility, and resilience. In order to establish local FRI, crucial local information have to be accumulated. However, under the limitation of land-use data, particular techniques were applied in this study. CA Markov model was used to analyze the past missing land-use data and, also forecast the future land-use of Pakpanang river basin under conditions of plan and without plan. The ratio changes of forest, agriculture, wetland and water, and urban areas were considered. Then, the result of LULC spatial-temporal changes was then applied to Hec-HMS and Hec-Ras , with Arc GIS extension of Hec-GeoHMS and Hec-GeoRas software, in order to evaluate the flood hydrographs and flood severity in three municipalities corresponding to 100-year return period rainfall. Afterward, the FRI of Pakpanang, Chianyai, and Hua-sai, which ranges from 0 to 1, were evaluated by using the modified FRI equations. It was found that sensitivity analysis in the area of forest on flood depth and inundation areas is incoherent. Nevertheless, without land-use planning, the changes in these three cities cause higher flood risk, where Chianyai is the riskiest as the FRIE is 0.58. Further consideration of FRIE and FRIP proportion that reveals the FRI deviation indicates that to reduce flood risk, Chianyai would need the most resources and highest effort comparison to Pakpanang and Hua-sai.

Delineation of Groundwater Potential Zone and Flood Risk Zone in Cachar District area,India

Cachar district is one of the most populated districts of Assam, India. The region has been exposed to frequent catastrophic flood during monsoon which is responsible for sufferings of the community. The uncertain or shifting pattern of rain in recent times apart from usual monsoon has further escalated the woes of this area. The LOOK EAST POLICY and quest for the development of this part is causing rapid industrialisation and urbanisation, which demands an additional source of freshwater opposed to traditional demand in irrigation and other domestic needs in this region. This demand for freshwater is vertical in the graph and continuously rising. Consequently, the source of freshwater in the area is depleting and further mismanagement will be devastative for resources of water in the entire district. To satisfy the demand and to ensure sustainable development in the region, there is an urgent need for its conservation and management aimed to ameliorate water resources. With this idea behind the present investigation is to pinpoint flood risk zones as well as to demonstrate the variability in groundwater prospects in Cachar District, using geospatial technology. The study is based on thematic maps of Land Use/Land Cover (LULC), elevation, soil type, rainfall, lineament density, drainage density, slope, and aspect in a Geographical Information System (GIS) environment. The groundwater potential zone (hereinafter, GWPZ) areas have been classified into five zones, viz; Very low, Poor, Moderate, Good, and Very Good. About 74.37% of the total area comes under Moderate GWPZ. To identify Flood Risk areas, the whole district has been categorised into Very Low, Low, Moderate, High, and Very High, risk flood zones. About 50.47% of the total area of Cachar District has been found under Moderate flood risk zone. The study at hand may help decision-makers in identifying the GWPZ and earmarking High-Risk Flood Zones for the planning of integrated water resources management.