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

2021 ◽  
Vol 4 (1) ◽  
Keyword(s):  
Risk Assessment ◽  
Flood Risk ◽  
Disaster Preparedness ◽  
Niger Delta ◽  
Sampling Technique ◽  
Flood Hazards ◽  
River Channels ◽  
Social Infrastructure ◽  
Entire Study ◽  
Flood Exposure

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.

scholarly journals Building Asset Value Mapping in Support of Flood Risk Assessments: A Case Study of Shanghai, China

2019 ◽  
Vol 11 (4) ◽  
pp. 971 ◽  
Author(s):  
Jidong Wu ◽  
Mengqi Ye ◽  
Xu Wang ◽  
Elco Koks
Keyword(s):  
Risk Assessment ◽  
High Resolution ◽  
Population Density ◽  
Flood Risk ◽  
Statistical Data ◽  
Risk Assessments ◽  
Flood Hazards ◽  
Grid Data ◽  
Flood Exposure ◽  
Asset Value

Exposure is an integral part of any natural disaster risk assessment, and damage to buildings is one of the most important consequence of flood disasters. As such, estimates of the building stock and the values at risk can assist in flood risk management, including determining the damage extent and severity. Unfortunately, little information about building asset value, and especially its spatial distributions, is readily available in most countries. This is certainly true in China, given that the statistical data on building floor area (BFA) is collected by administrative entities (i.e. census level). To bridge the gap between census-level BFA data and geo-coded building asset value data, this article introduces a method for building asset value mapping, using Shanghai as an example. This method consists of a census-level BFA disaggregation (downscaling) by means of a building footprint map extracted from high-resolution remote sensing data, combined with LandScan population density grid data and a financial appraisal of building asset values. Validation with statistical data and field survey data confirms that the method can produce good results, but largely constrained by the resolution of the population density grid used. However, compared with other models with no disaggregation in flood exposure assessment that involves Shanghai, the building asset value mapping method used in this study has a comparative advantage, and it will provide a quick way to produce a building asset value map for regional flood risk assessments. We argue that a sound flood risk assessment should be based on a high-resolution—individual building-based—building asset value map because of the high spatial heterogeneity of flood hazards.

scholarly journals Environmental Inequalities in Flood Exposure: A Matter of Scale

2021 ◽  
Vol 3 ◽  
Author(s):  
Clémence Poussard ◽  
Benjamin Dewals ◽  
Pierre Archambeau ◽  
Jacques Teller
Keyword(s):  
Flood Risk ◽  
Flood Hazard ◽  
Economic Status ◽  
Flood Hazards ◽  
Socio Economic Status ◽  
Flood Exposure ◽  
Class 1 ◽  
Riverine Floods ◽  
Peripheral Areas ◽  
Hazard Level

Studies on inequalities in exposure to flood risk have explored whether population of a lower socio-economic status are more exposed to flood hazard. While evidence exist for coastal flooding, little is known on inequalities for riverine floods. This paper addresses two issues: (1) is the weakest population, in socio-economic terms, more exposed to flood hazard, considering different levels of exposure to hazard? (2) Is the exposure to flood risk homogeneous across the territory, considering different scales of analysis? An analysis of the exposure of inhabitants of Liège province to flood risk was conducted at different scales (province, districts, and municipalities), considering three levels of exposure to flood hazard (level 1- low hazard, level 3- high hazard), and five socio-economic classes (class 1-poorest, class 5-wealthiest households). Our analysis confirms that weaker populations (classes 2 and 3) are usually more exposed to flood hazards than the wealthiest (classes 4 and 5). Still it should be stressed that the most precarious households (class 1) are less exposed than low to medium-range ones (classes 2 and 3). Further on the relation between socio-economic status and exposure to flood hazard varies along the spatial scale considered. At the district level, it appears that classes 4 and 5 are most exposed to flood risk in some peripheral areas. In municipalities located around the center of the city, differences of exposure to risk are not significant.

scholarly journals An Analysis of Existing Housing Stock in Selected Neighbourhoods in Port Harcourt Municipality

2021 ◽  
Vol 2 (3) ◽  
pp. 57-61
Author(s):  
Ibisiki T. Godwill ◽  
O. B. Owei ◽  
Ibama Brown
Keyword(s):  
Physical Condition ◽  
Housing Stock ◽  
Sampling Technique ◽  
Simple Random Sampling ◽  
Social Infrastructure ◽  
Entire Study ◽  
Multi Stage ◽  
Port Harcourt ◽  
Existing Housing

The housing stock in Port Harcourt municipality has over the years experienced incremental deterioration from neglect to change of use, paucity of funds and sometimes misappropriation of resources. The study assessed existing housing stock within Port Harcourt municipality with the objective to ascertain the physical condition of the housing stock in some planned and unplanned neighbourhoods in Orije layout-Orominike (D/Line), Port Harcourt Township and Diobu (Mile1 and Mile 2) and some waterfront settlements. Twenty-five (25) communities were identified from the entire study area. Some indicators such as habitable space, physical condition, availability of basic social infrastructure and services and environmental quality of the housing unit were measured. The sample was drawn purposively as 4 distinct neighbourhoods were studied. A multi-stage sampling technique was deployed, Taro Yamane formula was applied to determine the sample size of 156, as the number of questionnaires to be administered and stratified simple random sampling technique was employed to select respondents with household 5 persons per household of which 148 questionnaires were retrieved. Data from the field were analysed using Statistical Package for Social Sciences (SPSS), aimed at comparing the nature of substandard housing found across the neighbourhoods studied. The result indicates that the housing stock in the indigenous enclaves within the Diobu neighbourhood has a high occupancy ratio and lacked basic public utilities and services in addition to houses being constructed with substandard materials. Residents often experience periodic flooding after rainfalls. The study recommends that to further improve the standard of housing conditions in line with the global UN standards, the provision of basic social infrastructural services alongside periodic and consistent urban renewal processes should be constantly carried out to reduce the housing deficit within the municipality.

scholarly journals A rainfall design method for spatial flood risk assessment: considering multiple flood sources

2015 ◽  
Vol 12 (8) ◽  
pp. 8005-8033 ◽  
Author(s):  
X. Jiang ◽  
H. Tatano
Keyword(s):  
Risk Assessment ◽  
Risk Management ◽  
Flood Risk ◽  
Urban Areas ◽  
Design Method ◽  
Coastal Flooding ◽  
Flood Risk Management ◽  
Flood Risk Assessment ◽  
River Channels ◽  
Critical Rainfall

Abstract. Information about the spatial distribution of flood risk is important for integrated urban flood risk management. Focusing on urban areas, spatial flood risk assessment must reflect all risk information derived from multiple flood sources: rivers, drainage, coastal flooding etc. that may affect the area. However, conventional flood risk assessment deals with each flood source independently, which leads to an underestimation of flood risk in the floodplain. Even in floodplains that have no risk from coastal flooding, flooding from river channels and inundation caused by insufficient drainage capacity should be considered simultaneously. For integrated flood risk management, it is necessary to establish a methodology to estimate flood risk distribution across a floodplain. In this paper, a rainfall design method for spatial flood risk assessment, which considers the joint effects of multiple flood sources, is proposed. The concept of critical rainfall duration determined by the concentration time of flooding is introduced to connect response characteristics of different flood sources with rainfall. A copula method is then adopted to capture the correlation of rainfall amount with different critical rainfall durations. Rainfall events are designed taking advantage of the copula structure of correlation and marginal distribution of rainfall amounts within different critical rainfall durations. A case study in the Otsu River Basin, Osaka prefecture, Japan was conducted to demonstrate this methodology.

Urban Flood Risk Assessment and Development of Urban Flood Resilient Spatial Plan for Bhubaneswar

2021 ◽  
Vol 12 (2) ◽  
pp. 269-291
Author(s):  
Alisa Sahu ◽  
Tushar Bose ◽  
Dipak R. Samal
Keyword(s):  
Risk Assessment ◽  
Land Use ◽  
Land Use Planning ◽  
Flood Risk ◽  
Flood Hazard ◽  
Geographic Area ◽  
Spatial Modelling ◽  
Disaster Risk ◽  
Flood Hazards ◽  
Urban Flood

Urban flooding is growing as a serious development challenge for cities. Urbanization demands the conversion of pervious land to impervious land by pushing the transformation of water bodies, flood plains, wetlands and green spaces into built-up spaces. This affects the hydrological setting of the city’s geographic area. Bhubaneswar, one of the first planned cities of independent India, has expanded rapidly with an increase in the settlement land use cover from 41 km2 to 81 km2 in the last two decades. Non-consideration of disaster risk assessment in the land use plan has placed the city at high disaster risk. Hence, this article explores various avenues for making a flood resilient city through spatial planning. To understand the flood and its consequences, a flood hazard and vulnerability map was prepared by overlaying the existing social and infrastructure networks, and flood risk zones were generated through analytical spatial modelling in GIS. This accounts for the areas in which flood hazards are expected to occur, as well as the area whose socio-economic and infrastructure susceptibility to the disaster is more. The key outcome is to ensure urban development that can work concurrently with nature by integrating disaster risk reduction strategies into land use planning.

scholarly journals Event generation for probabilistic flood risk modelling: multi-site peak flow dependence model vs. weather-generator-based approach

2020 ◽  
Vol 20 (6) ◽  
pp. 1689-1703 ◽  
Author(s):  
Benjamin Winter ◽  
Klaus Schneeberger ◽  
Kristian Förster ◽  
Sergiy Vorogushyn
Keyword(s):  
Risk Assessment ◽  
Return Period ◽  
Flood Risk ◽  
Flood Damage ◽  
Weather Generator ◽  
Process Models ◽  
Flood Events ◽  
Entire Study ◽  
Advantages And Disadvantages ◽  
Peak Discharges

Abstract. Flood risk assessment is an important prerequisite for risk management decisions. To estimate the risk, i.e. the probability of damage, flood damage needs to be either systematically recorded over a long period or modelled for a series of synthetically generated flood events. Since damage records are typically rare, time series of plausible, spatially coherent event precipitation or peak discharges need to be generated to drive the chain of process models. In the present study, synthetic flood events are generated by two different approaches to modelling flood risk in a meso-scale alpine study area (Vorarlberg, Austria). The first approach is based on the semi-conditional multi-variate dependence model applied to discharge series. The second approach relies on the continuous hydrological modelling of synthetic meteorological fields generated by a multi-site weather generator and using an hourly disaggregation scheme. The results of the two approaches are compared in terms of simulated spatial patterns of peak discharges and overall flood risk estimates. It could be demonstrated that both methods are valid approaches for risk assessment with specific advantages and disadvantages. Both methods are superior to the traditional assumption of a uniform return period, where risk is computed by assuming a homogeneous return period (e.g. 100-year flood) across the entire study area.

scholarly journals Event generation for probabilistic flood risk modelling: multi-site peak flow dependence model vs weather generator based approach

2020 ◽  
Author(s):  
Benjamin Winter ◽  
Klaus Schneeberger ◽  
Sergiy Vorogushyn
Keyword(s):  
Risk Assessment ◽  
Return Period ◽  
Flood Risk ◽  
Weather Generator ◽  
Process Models ◽  
Flood Events ◽  
Entire Study ◽  
Advantages And Disadvantages ◽  
Traditional Assumption ◽  
Entire Study Area

Abstract. Flood risk assessment is an important prerequisite for risk management decisions. To estimate the risk, flood damages need to be either systematically recorded over long period or they need to be modelled for a series of synthetically generated flood events. Since damage records are typically rare, time series of plausible, spatially coherent event precipitation or peak discharges need to be generated to drive the chain of process models. In the present study, synthetic flood events are generated by two different approaches to model flood risk in a meso-scale alpine study area (Vorarlberg, Austria). The first approach is based on the semi-conditional multi-variate dependence model applied to discharge series. The second approach is based on the continuous hydrological modelling of synthetic meteorological fields generated by a multi-site weather generator and using an hourly disaggregation scheme. The results of the two approaches are compared in terms of simulated spatial patterns and overall flood risk estimates. It could be demonstrated that both methods are valid approaches for risk assessment with specific advantages and disadvantages. Both methods are superior to the traditional assumption of a uniform return period, where risk is computed by assuming a homogeneous return period (e.g. 100-year flood) across the entire study area.

scholarly journals Effectiveness of Water Infrastructure for River Flood Management: Part 2 – Flood Risk Assessment and Its Changes in Bangladesh

2015 ◽  
Vol 370 ◽  
pp. 83-87 ◽  
Author(s):  
Y. Kwak ◽  
M. Gusyev ◽  
B. Arifuzzaman ◽  
I. Khairul ◽  
Y. Iwami ◽  
...  
Keyword(s):  
Risk Assessment ◽  
Flood Risk ◽  
Flood Hazard ◽  
Rice Paddy ◽  
Rice Crop ◽  
Crop Damage ◽  
Water Infrastructure ◽  
Flood Hazards ◽  
Coping Capacity ◽  
River Flood

Abstract. A case study of Bangladesh presents a methodological possibility based on a global approach for assessing river flood risk and its changes considering flood hazard, exposure, basic vulnerability and coping capacity. This study consists of two parts in the issue of flood change: hazard assessment (Part 1) and risk assessment (Part 2). In Part 1, a hazard modeling technology was introduced and applied to the Ganges, Brahmaputra and Meghna (GBM) basin to quantify the change of 50- and 100-year flood hazards in Bangladesh under the present (1979–2003) and future (2075–2099) climates. Part 2 focuses on estimating nationwide flood risk in terms of affected people and rice crop damage due to a 50-year flood hazard identified in Part 1, and quantifying flood risk changes between the presence and absence of existing water infrastructure (i.e., embankments). To assess flood risk in terms of rice crop damage, rice paddy fields were extracted and flood stage-damage curves were created for maximum risk scenarios as a demonstration of risk change in the present and future climates. The preliminary results in Bangladesh show that a tendency of flood risk change strongly depends on the temporal and spatial dynamics of exposure and vulnerability such as distributed population and effectiveness of water infrastructure, which suggests that the proposed methodology is applicable anywhere in the world.

scholarly journals Vulnerability of human settlements to flood risk in the core area of Ibadan metropolis, Nigeria

2017 ◽  
Vol 9 (1) ◽  
Author(s):  
Rafiu O. Salami ◽  
Jason K. Von Meding ◽  
Helen Giggins
Keyword(s):  
Risk Reduction ◽  
Flood Risk ◽  
Disaster Preparedness ◽  
Disaster Risk Reduction ◽  
Disaster Risk ◽  
Flood Disaster ◽  
Economic Losses ◽  
Flood Hazards ◽  
Effective Response ◽  
Coping Capacity

Flood disasters continue to wreak havoc on the lives of millions of people worldwide, causing death and massive economic losses. In most African cities, residents and their assets are among the most vulnerable to flood risks in the world. The nature and scale of this urban risk are changing because of the dynamic patterns of land use, unplanned growth and impacts of climate change. Flood risk is the product of the flood hazards, the vulnerability and exposure of the people and their physical environment. In order to minimise flood disaster, there is an urgent need to understand, invest in flood disaster risk reduction for resilience and to enhance disaster preparedness for an effective response as articulated in the recent Sendai Framework for Disaster Risk Reduction. This research utilises a new proposed flood vulnerability assessment framework for flood risk in a traditional community in the heart of Ibadan metropolis, in the context of their households’ exposure, susceptibility and coping capacity through a well-designed questionnaire survey. The study uses descriptive and inferential statistics techniques to provide a detailed understanding of the vulnerability profiles of the community and the levels of residents’ preparedness to mitigate the flood risk. The results of the statistical analysis show that there is a significant relationship between residents’ flood awareness and having previous flood experience, but there is no significant association between their awareness of risk and the level of preparedness for flooding. To minimise exposure and vulnerability to flood risk, we advocate effective adaptation policies to achieve disaster risk reduction and resilience on flood risk rather than focusing merely on reactive measures after disaster strikes.

Flood Risk Assessment and Forecasting for the Ganges-Brahmaputra-Meghna River Basins

10.1596/28574 ◽  
2017 ◽  
Author(s):  
Satya Priya ◽  
William Young ◽  
Thomas Hopson ◽  
Ankit Avasthi
Keyword(s):  
Risk Assessment ◽  
Flood Risk ◽  
River Basins ◽  
Flood Risk Assessment ◽  
The Ganges
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