scholarly journals Application of Geographic Information Systems for Flood Risk Analysis: A Case Study from Accra Metropolitan Area

2019 ◽  
Vol 13 (1) ◽  
pp. 81-97
Author(s):  
Alex Barimah Owusu ◽  
Mathias Agbozo
Keyword(s):  
Flood Risk ◽  
Drainage Density ◽  
Low Risk ◽  
Soil Drainage ◽  
Risk Area ◽  
The Public ◽  
Risk Areas ◽  
Risk Zones ◽  
High Flood

Abstract The main objective of the study was to identify high flood risk zones in AMA. The study also used questionnaires to assess local knowledge on what accounts for the high flood risk in their community. Spatial analysis techniques were used to model flood risk based on the following contributory factors; land cover, soil, drainage density, topography and proximity to rivers. The results show that high flood risk areas covered 46.3km2(20%), moderate risk area, 72.9km2(31.6%), low risk area 41.5km2(18%) and very low risk areas, about 6.7km2(2.9%). The high flood risk zones were low-lying areas below 50 meters above sea level and closely associated with poor drainage systems. People perceived not just low-lying areas as a paramount reason accounting for flooding but also very bad waste disposal habit of the public. These offsets the efforts of waste management companies to keep drains free of refuse.

scholarly journals Identificação e mapeamento das áreas de risco no município de Itajaí- SC a partir das inundações ocorridas em 2011 (Identification and mapping of the flood risk areas in the city of Itajaí-SC based on the 2011 floods)

2016 ◽  
Vol 9 (6) ◽  
pp. 1895
Author(s):  
André Jesus Periçato ◽  
Valdeir Demétrio da Silva ◽  
Francieli Sant'ana Marcatto
Keyword(s):  
Urban Space ◽  
Flood Risk ◽  
Urban Areas ◽  
Historical Analysis ◽  
Risk Map ◽  
Risk Area ◽  
Control And Prevention ◽  
Risk Areas ◽  
High Flood ◽  
The City

A ocorrência de inundações em áreas urbanas tem se intensificado nos últimos anos, ocasionando diversos danos e prejuízos para a sociedade. O intenso crescimento das cidades nas últimas décadas, assim como a ocupação irregular do espaço urbano com moradias precárias e próximas aos rios, são fatores determinantes para que ocorram essas situações de catástrofes. O objetivo deste trabalho é mapear e identificar as áreas de inundação em setembro de 2011 no município de Itajaí para a confecção do mapa de risco. Para isso foi realizado uma análise histórica do crescimento da malha urbana de Itajaí, correlacionando com as manchas de inundação. Os resultados obtidos revelaram que a inundação ocorrida em 2011 atingiu parte significativa da área do município, com destaque ao perímetro urbano. Os pontos mais críticos de inundação foram às áreas onde houve o crescimento urbano, com destaque as proximidades do rio Itajaí-Mirim. Foi possível analisar por meio do mapa de risco, que grande parte da cidade de Itajaí foi classificada com um alto índice de risco a inundação. Deste modo, pode-se concluir que o mapeamento das áreas de risco configura-se como uma importante ferramenta e instrumento no controle e prevenção à inundação em áreas afetadas por esse fenômeno.   A B S T R A C T The occurrence of floods in urban areas has intensified in the recent years, causing many kinds od damage and loss for society. The intense growth of the cities in the past few decades, along with the irregular occupation of urban space with precarious settlements close to the rivers, were determining factors for these catastrophic situations to occur. The objective of this study is mapping and identifying the flooding areas in September 2011 in the city of Itajaí for the confection of a risk map. For this a historical analysis of the growth of the Itajaí urban area was realized, correlating with the flood spots. The obtained results reveal that the 2011 floods affected a significant portion of the city’s area, especially the urban perimeter. The most critical flood spots were in the areas where urban growth took place, especially nearby the Itajaí-Mirim river. By analizing the map, it’s noted that a big part of the city of Itajaí is classified as a high flood risk area. It can be concluded that the mapping of risk areas is an important tool and instrument in the control and prevention of floods in the areas affected by this phenomenon. Keywords: urban flooding, geotechnology, flood risk map.   

Cries in the Dark: Reconstruction after Hurricane Mitch in Honduras

2006 ◽  
Vol 31 (1) ◽  
pp. 31-38
Author(s):  
Kurt Rhyner
Keyword(s):  
High Risk ◽  
Low Cost ◽  
Construction Materials ◽  
Natural Phenomenon ◽  
Police Chief ◽  
Hurricane Mitch ◽  
The Public ◽  
Risk Areas ◽  
Mountainous River

Disasters are always caused by a combination of factors, and the natural phenomenon that brings them on is usually just a catalyst. The underlying cause of most disasters is poverty as mostly the poor segments of the population usually live in high risk areas where their shelter all too often cannot withstand even light winds, small inundations or medium earthquakes. When Hurricane Mitch hit Central America in October 1998, all countries were ill prepared. A few weeks earlier, the authorities of the Honduran capital, Tegucigalpa, had attempted to simulate an evacuation, but it had met with a great degree of resistance from the public. When Mitch hit, unprecedented masses of water raced down the mountainous river beds. People were taken by surprise, as no efficient organisation existed. Everybody ran for their lives. Houses slid down hillsides, rivers swept bridges, houses and people with them. Six years later, Tegucigalpa looks very similar to the days before Mitch. The steep hillsides are covered with a potpourri of dwellings, from miserable huts to solid upmarket houses. Regulations were passed in the year 2002 to prohibit construction in high risk areas; however, enforcement is difficult, especially when existing buildings are renovated and even enlarged. Theoretically it is possible to evacuate high risk areas. Nonetheless, such drastic measures are virtually impossible to implement, as no mayor or police chief would survive such an action in office. The paper presents a case study which shows that the underlying problems of poverty and the non-availability of suitable land for people to relocate from high risk areas can usually not be overcome by post-disaster reconstruction programmes. A mitigation strategy is thus to empower inhabitants of high risk areas to improve their own situation by affordable access to information, advice and suitable low cost construction materials through “Building Advisory Services” and Ecomaterials producers within the neighbourhoods.

scholarly journals Flood-Prone Area Assessment Using GIS-Based Multi-Criteria Analysis: A Case Study in Davao Oriental, Philippines

Water ◽  
2019 ◽  
Vol 11 (11) ◽  
pp. 2203 ◽  
Author(s):  
Cabrera ◽  
Lee
Keyword(s):  
Flood Risk ◽  
Flood Hazard ◽  
Drainage Density ◽  
Mitigation Strategies ◽  
Risk Area ◽  
Analytic Hierarchy ◽  
Comparison Results ◽  
Prone Area ◽  
Ground Truthing ◽  
Very High

Flooding is one of the major destructive natural disasters in Davao Oriental, Philippines, and results primarily from a high incidence of typhoons and heavy rainfalls. The main objective of this study was to identify flood-prone risk areas by mapping them based on the integration of multiple indicators, including rainfall, slope, elevation, drainage density, soil type, distance to the main channel and population density. For this purpose, a GIS-based flood risk spatial assessment was conducted by using analytic hierarchy process (AHP), weights by rank (WR) and ratio weighting (RW) frameworks to determine the relative importance of each indicator against another in the province of Davao Oriental. The resulting flood-prone areas by the three methods are validated by comparing with the estimated flood map based on ground truthing points from a field survey. The comparison results show that AHP is the most appropriate method among them to assess flood hazard. The result of the AHP flood risk map shows that 95.99% (5451.27 km2) of Davao Oriental is under low and moderate flood risk. The high and very high flood risk area covers approximately 3.39% (192.52 km2) of the province, primarily in the coastal areas. Thirty-one out of the one hundred eighty-three (31/183) barangays (towns) are at a high to very high risk of flooding at current climate, calling for the immediate attention of decision-makers to develop mitigation strategies for the future occurrence of flooding in Davao Oriental.

scholarly journals Evaluation of Flood Management in Nigeria: A Case Study of Yauri Local Government Area, Kebbi State

2019 ◽  
pp. 652-659
Author(s):  
Daniel Habila Galadima ◽  
Ishaya K. Samaila ◽  
Magaji I. Joshua
Keyword(s):  
Local Government ◽  
Flood Management ◽  
Drainage Density ◽  
Local Government Area ◽  
Data Set ◽  
Topographical Map ◽  
Gis Environment ◽  
High Flood ◽  
Pair Wise Comparison

An evaluation of management in Nigeria with focus on Yauri Local Government Area of Kebbi State was carried out. The study made use of ASTER data of 2017 with spatial resolution of 30m, topographical map at a scale of 1:50,000, monthly rainfall data for 35 covering the study area and soil map at a scale of 1:50,000. Thematic maps for soil, rainfall and elevation were produced converted to raster data in GIS environment. Each data set in a single map was given weight by pair-wise comparison; reclassification of each map was done based on the weights generated from the pair-wise comparison of each dataset. The weights generated revealed that rainfall with 46 as its weight has the greatest influence on flood occurrences in the study area. Elevation accounted for weights of 24, slope accounted for 12 while drainage density, soil and LULC accounted for 10, 8 and 3 respectively. The settlements of Gumbi, Yauri, Unguwa Damisa, Zamare and Jijima that make up the study area lie along the zone of very high flood vulnerable land. Among the causes of flooding, excess rainfall and coastal location of the various settlements are responsible for flooding. Besides, the relief of the study area is such that encourage flooding as all the settlements are situated along the river course. The predominant coping and adapting strategies adopted to check flooding in the study area are temporary relocation and the raising of the floor of their houses among others.

scholarly journals Flood risk assessment in selected communes of the Łódź region

2017 ◽  
pp. 21-41
Author(s):  
Marta Borowska-Stefańska
Keyword(s):  
Flood Risk ◽  
Land Development ◽  
Risk Level ◽  
Individual Risk ◽  
Negative Consequences ◽  
Risk Levels ◽  
Risk Areas ◽  
High Flood ◽  
Very High ◽  
Risk Categories

The aim of the article is to assess the present level of land development of flood risk areas in selected communes of the Łódź province in the context of potential negative consequences for people, the natural environment, cultural heritage and economic operations. The research includes urban as well as urban and rural communes (9 communes in total) of the Łódź province which display high and very high flood risk levels according to the methodology used in Flood protection operating plan for the Łódź province from 2013 ( Plan operacyjny… 2013). Uniejów and Warta have the highest synthetic flood risk levels due to the surface occupied by buildings and areas assigned to individual risk categories. In turn, Łowicz and Tomaszów Mazowiecki (town) display the highest general flood risk level due to diversification of buildings and areas of individual risk categories.

scholarly journals Flash Flood Susceptibility Assessment and Zonation Using an Integrating Analytic Hierarchy Process and Frequency Ratio Model for the Chitral District, Khyber Pakhtunkhwa, Pakistan

Water ◽  
2021 ◽  
Vol 13 (12) ◽  
pp. 1650
Author(s):  
Hassan Waqas ◽  
Linlin Lu ◽  
Aqil Tariq ◽  
Qingting Li ◽  
Muhammad Fahad Baqa ◽  
...  
Keyword(s):  
High Risk ◽  
Frequency Ratio ◽  
Flash Flood ◽  
Drainage Density ◽  
Low Risk ◽  
Physical Parameters ◽  
Observation Data ◽  
Risk Zones ◽  
Hierarchy Process ◽  
Very High

Pakistan is a flood-prone country and almost every year, it is hit by floods of varying magnitudes. This study was conducted to generate a flash flood map using analytical hierarchy process (AHP) and frequency ratio (FR) models in the ArcGIS 10.6 environment. Eight flash-flood-causing physical parameters were considered for this study. Five parameters were based on the digital elevation model (DEM), Advanced Land Observation Satellite (ALOS), and Sentinel-2 satellite, including distance from the river and drainage density slope, elevation, and land cover, respectively. Two other parameters were geology and soil, consisting of different rock and soil formations, respectively, where both layers were classified based on their resistance against water percolation. One parameter was rainfall. Rainfall observation data obtained from five meteorological stations exist close to the Chitral District, Pakistan. According to its significant importance in the occurrence of a flash flood, each criterion was allotted an estimated weight with the help of AHP and FR. In the end, all the parameters were integrated using weighted overlay analysis in which the influence value of the drainage density was given the highest value. This gave the output in terms of five flood risk zones: very high risk, high risk, moderate risk, low risk, and very low risk. According to the results, 1168 km2, that is, 8% of the total area, showed a very high risk of flood occurrence. Reshun, Mastuj, Booni, Colony, and some other villages were identified as high-risk zones of the study area, which have been drastically damaged many times by flash floods. This study is pioneering in its field and provides policy guidelines for risk managers, emergency and disaster response services, urban and infrastructure planners, hydrologists, and climate scientists.

scholarly journals Flood Risk Zoning of Satluj River Basin, Himachal Pradesh, India

2015 ◽  
Vol 40 ◽  
pp. 6-15 ◽  
Author(s):  
Sandeep Kumar ◽  
Santosh
Keyword(s):  
At Risk ◽  
Land Use ◽  
River Basin ◽  
Flood Risk ◽  
Low Risk ◽  
Risk Zone ◽  
Risk Zoning ◽  
Risk Zones ◽  
Satluj River ◽  
Very High

Increasing intensity and frequency of rainfall coupled with gradual retreating of glaciers due to climate change in Himalayan region likely to increase the risk of floods. A better understanding of risk zones which are vulnerable to flood disasters can be evolved from the detailed studies on slope, geomorphology and land use/ land cover pattern. Information of these parameters is an important input for the identification of vulnerable areas. Flood risk maps provide useful information about places that may be at risk from flooding. It offers a cost-effective solution for planning, management and mitigation strategies in risky areas. Traditional methods of flood risk mapping are based on ground surveys and aerial observations, but when the phenomenon is widespread, such methods are time consuming and expensive. The possible combination of DEM and other maps of area using an overlay operation method within the Geographical Information System (GIS) platform can lead to derivation and the understanding of spatial association between various parameters which could be used to predict flood risk zones. The study area i.e. Satluj River Basin has been broadly divided into five risk zones viz., very low, low, moderate, high and very high which helped to differentiate between areas that are at risk of different intensities of flood. The very high flood risk zone covers only 3.25 % of total study area, while the very low risk zone covers 13.63 %. The area falls within the very high and high risk constitutes 9.52 % of total basin area. Domain of moderate risk covers an area of 30.66 %. But the maximum area of river basin is constituted by low risk zone i.e. 46.19 %. Identification of such zones will help in timely adopting of mitigation and adaptation measures. Preparation of flood risk zoning maps also helps in regulating indiscriminate and unplanned land use practices in risky areas.

scholarly journals Flood vulnerability reduction. Case study: Tazlău river basin, downstream of its confluence with Tazlău Sărat

2021 ◽  
Vol 15 (2) ◽  
pp. 189-198
Author(s):  
Alina Tirnovan ◽  
Ovidiu Covaci ◽  
Marius Robert Gazda ◽  
Narcis Barsan ◽  
Andrei Enea
Keyword(s):  
River Basin ◽  
Flood Risk ◽  
Left Bank ◽  
The European Union ◽  
Risk Area ◽  
Flood Vulnerability ◽  
Management Plans ◽  
Reduction Case ◽  
Flood Risk Management Plans

The issue of water management as well as its impact on the community has been both a challenge and a concern of the European Union, which lead to adopting the Directive 2007/60/EC with the purpose of establishing a framework for the assessment and management of flood risks, by which the member states had to identify the areas for which they conclude that potential significant flood risk exist or likely to occur and to develop flood risk management plans and measures to reduce the consequences of flooding. In this respect, the Siret Water Basin Administration has declared the area of the Tazlău river, as a significant flood risk area (A.P.F.S.R.) (*** A.B.A Siret). The Tazlău River is a left-bank tributary to the Trotuș River, passing through the ten communes and partially through the outside the built-up areas of Onești city. Recent studies have shown the benefits of reservoirs and floodplains, as these provide the most effective way to buffer the effect of floods by slowing and spreading the discharge of a river (Băloi, 1980). By restoring and improving an existing lateral floodplain in the Tazlău River basin, in order to store part of the floodwaters that cause significant adverse consequences, will reduce the flood vulnerability of its crossings.

scholarly journals Landscape ecological risk assessment and spatiotemporal change analysis in Yonghe County

2021 ◽  
Vol 237 ◽  
pp. 04038
Author(s):  
Jixuan Yan ◽  
Guang Li ◽  
Haiyan Wang ◽  
Meihua Zhang ◽  
Dongyuan Sun ◽  
...  
Keyword(s):  
Ecological Risk ◽  
Arable Land ◽  
Low Risk ◽  
Risk Level ◽  
Distribution Analysis ◽  
Risk Area ◽  
Change Analysis ◽  
Landscape Type ◽  
Risk Areas ◽  
Landscape Ecological

On the basis of land use data, combined with ArcGIS and fragstats4.2, the landscape ecological risk spatial mode and process feature of Yonghe county from 1980 to 2018 were analyzed. The results showed that: (1) from 1980 to 2018, the landscape pattern of Yonghe county changed obviously, the area of arable land and holt decreased, while the area of grassland, water and buildings grow a number. The conversion area between arable land and grassland is the largest. In Yonghe County, the fragmentation degree of landscape is on the rise, and the separation degree is also on the rise. The overall dominance of construction land is the largest, and the dominance of grassland is the smallest. (2) The landscape ecological risk level gradually subsided, the area of middle risk area decreased, and moderate risk areas are falling. From the spatial distribution analysis, the risk types of Yonghe County subsided from southeast to northwest. The high-risk areas were principally scattered in sangbi town and Jiaokou township. The main landscape type in this area was grassland, which was easily disturbed by human activities; the low-risk areas were principally scattered in Potou Township in the north and Yonghe County in the middle of the study area, and Woodland and buildings are the main landscape types land have strong anti-interference ability and low risk value.

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