Assessing the Safety of Settlements from Flood Risk

2007

Accurate and detailed terrain model are essential for hydrodynamics modelling especially in urban area. However, one of the main problems is frequent changes of land use in major cities, where frequent updating of the digital terrain model (DTM) for flood modelling might ...

GI_Forum, 2019

Under scenarios of urbanization coupled with increasing frequency and intensity of natural hazards, urban disaster risk is set to rise. Simulating future urban expansion can provide relevant information for the development of future exposure scenarios and the identification of targeted risk reduction and adaptation strategies. Here, we present an urban growth simulation for the coastal city of Monastir, Tunisia. The approach integrates local knowledge and a data-driven urban growth model to simulate urban sprawl up to 2030. A business-as-usual projection is used to predict the future growth of the city based on the historical trend. Thirteen Landsat images for the period 1975 to 2017 were used to delineate past changes in urban land cover following the European Urban Atlas standard, which served as the main input for the urban growth model. The simulation revealed that the city's residential area is likely to grow by 127 ha to an overall size of 1,690 ha by 2030, corresponding to an increase of 8.1% compared to the urban footprint of 2017. The outcomes of the analysis presented here served as an input for the spatial simulation of future exposure to flash floods in the case study area.

Journal of Water and Land Development

During the last few years, the City of Bechar in Algeria has witnessed some extreme events, such as the great flood of the year 2008 in which an exceptional amount of rain was recorded with a flow rate of 830 m3∙s−1 (hwater = 4 m, b = 200 m); similar flooding also occurred in 2012 and 2014. The problem is that most of the City of Bechar has an urban sprawl that extends to the banks of Wadi Bechar, which represents a huge risk for the lives of the inhabitants of the region. The present work aims to assess the flood risk through flood hazard mapping. This method consists in determining the flow rates for the return periods of 25 years (Q25 = 388.6 m3∙s−1, hwater = 3.5 m, b = 200 m, Sspot = 55.35 ha), 50 years (Q50 = 478.3 m3∙s−1, hwater = 5 m, b = 200 m, Sspot = 66.48 ha) and 100 years (Q100 = 567.3 m3∙s−1, hwater = 7 m, b = 200 m, Sspot = 133 ha). For this, it is necessary to adjust the flow rates using Gumbel law along with some computer supports such as HEC-RAS, HEC-GeoRAS and ArcG...

Comprehensive assessment of flood exposure in arid regions: Integrating GIS techniques and multi-method approaches – A case study of downstream swat river, Pakistan, 2024

International Journal of Sustainable Development and Planning

The climatic changes of the last 20 years generated a high rainfall intensity that lead a common flash flood risks in the wades of arid regions such as Mecca province. However, both the rapid urban expansion in that province and its small catchments trigger the flash flood risk. Therefore, a spatial plan that orient the urban expansion toward less potential flash flood risk has great importance. Such a plan is carried out by a spatial analysis for the topography, rainfall pattern, drainage network density and sub-catchment areas. Geographic Information Systems is a powerful tool in order for achieving that analysis by the overlaying method. Our research guide urban planner to where has urbanization extended. It is a preliminary study for an analytical and numerical runoff modelling that have to be done for the study area in order to clarify the flooding hazard. Our research indicates that catchment area size and drainage network density are the major two factors that control the spatial distribution of flash flooding and need to be consider for any urban spatial plan. We found that the four major cities in Mecca province are threaten by flash flooding differently in terms of direction and intensity.

Civil Engineering and Architecture, 2022

As a part of climate change; flash floods are rapidly increasing and becoming more severe, challenging more and more cities around the world. According to the recent facts published by the UN and the WHO, their risk increases particularly in low- and mid-income countries, where it exceeds the ability of communities to cope with it. This sheds the light on the importance of the community’s pre-impact conditions, which determine its vulnerability to floods. This research develops a vulnerability assessment tool and its associated methodology as an effective tool to be integrated into the strategic planning of existing cities facing flash floods. It is an indicators-based GIS tool to Assess Physical and Social vulnerability. Nuweiba city on the gulf of Aqaba-Egypt was chosen as a case study. However, it is located in an arid zone, and suffers from frequent and severe flash floods. It could be considered the effluent of Wadi Watir's main watershed (3509 km2). A GIS model has been developed to apply the Physical part of the developed assessment tool. So, Detailed data on the city’s urban structure, DEM and satellite images were integrated and processed to extract the evaluated layer for each vulnerability indicator. Then, a weighted overlay of these indicators was applied to produce the final vulnerability map. The results showed a high level of applicability for the developed model, however, the vulnerability map was compared to the available strategic plan for the city. Accordingly, several changes to the plan were recommended to achieve a more sustainable future for the city.

Civil Engineering Journal

Identifying risks in flood-prone areas is necessary to support risk management decisions. This research was conducted to establish a vulnerability model of flood hazards in the city of Pontianak. The model was based on the scoring and weighting of biophysical factors. The AHP method and logical formulations were used to establish the model. The result showed that the accuracy of the model used by AHP to determine the vulnerability of floods was 80% in Pontianak City. The accuracy of the model using logical formulations to determine the vulnerability level of a flood was 84%. The Kappa accuracy value in model 1 is 76.7%. The model of flood vulnerability explains that most of Pontianak City has a very high level of flood vulnerability, which is 31,440,568.8 m2 or 29.11% of the total research area of 108,003,319.8 m2. The vulnerable area is 29,945,485.7 m2 or 27.73%, and the less safe area is 22,126,936.3 m2 or 20.49%, with the safe area being 24,490,328.7 m2or 22.67% of the total area...

ERJ. Engineering Research Journal, 2012

GIS has gained considerable importance in engineering applications particularly in the fields of hydrology and hydraulics. The present paper assessed the risk of the Aswan High Dam, AHD breaching, numerically. Flood model was chosen and was selected to be implemented. The outflow hydrograph due to fail of AHD are considered as the output of Abdelhaleem F. study (2011). Then, SOBEK 1D2D model was implemented in order to simulate the flood wave propagation and inundation area in the Nile Valley. Geographical Information Systems, GIS tools was used to manage the input and output results, and also was used to produce a precise Digital Elevation Model, DEM to the Nile Valley, Egypt, and implemented in order to determine the banks violation sites together with the inundation of surrounding areas. So the size of expected damage of national main structures, (Railways, roads, airports, etc) within the extension of the study area was identified using GIS spatial database. The final obtained raster maps were handled and analyzed mutually with up-to-date maps of GIS thus more applicable results. The time of flood wave propagations along the Nile was calculated in order to define the time of response for emergency measures to be operated. The results could put forward to a flood management plan and could suggest evacuation plans.

International Journal of Innovative Studies in Sociology and Humanities, 2023

The study of floods is a topic of increasing interest in the field of risk management because it constitutes the most recurring natural disaster in the world that causes significant damage. Algeria is among the Mediterranean countries that are affected by sudden and unpredictable floods. According to the Algerian civil protection services, one out of three municipalities is likely to be flooded, in part or in full. In recent decades, extreme hydrological events have occurred in the arid city of M'chouneche. Their high frequency and dependence on climate change, in addition to the increasing demographic pressure on the shores of valleys, make them a cause for concern and difficult to manage. The use of empirical, hydrodynamic, or conceptual models and geographical information systems (GIS) has become a valuable approach for assessing natural hazards, especially floods. This work aims to simulate floods for a 10-year and 100-year return periods with a one-dimensional (1-D) model using HEC RAS (Hydrologic Engineering Centers River Analysis System) software, GIS (Geographic Information System), and remote sensing (RS). The result is a decision support tool for local authorities based on feedback experience from extreme hydrological events and flood frequency analysis for different return periods to identify probable flood scenarios and provide valuable decision support for emergency response and crisis management.

Jordanian Journal of Engineering and Chemical Industries, 2020

Jordan is located in an arid and semi-arid climatic zone, where about 80% of the country, known as the "Badia". Generally, this is classified as a dry or arid region. Climate change is expected to exacerbate the current aridity and scarcity of water resources in Jordan. Sudden and extreme weather events are becoming more common; this likely means longer and drier summers, more severe droughts, harsher winters, and an increase in flash floods. Jordanian Civil Defense reported that during 1963-2019, 451 people were killed and about one million people affected by flash floods. This research aims to determine the critical locations of flash floods in the Amman Zarqa Basin. This research methodology depends on using four variables (slope, vegetation cover/density, soil type/texture, and land use/cover) under the GIS environment to calculate the Flash Flood Potential Index (FFPI). This index has not been used in Jordan (up to our knowledge). Five scenarios were used in this study, based on previous reviews and the last one (scenario 5) based on Jordanian experts of flash floods in Jordan. The results show that increasing the weight of slope and land use in different FFPI equations will increase the values of FFPI. Reducing the vegetation density by 50% resulted in limited effects on the importance of FFPI. The risk level is divided into four categories (extreme, high, medium, and low) related to the FFPI values. Scenario two, which uses equal weights for all parameters, had the lowest risk level all over the area. Scenario four, which double the consequences of the slope and the land use with respect to the other two parameters. This has the highest risk level over the study area. Based on equation no. 5, which is modified based on Jordanian experts' opinion, the low-risk level covered 9.01% of the basin. Besides, the medium, high, and extreme risk levels covered 72.96%, 15.89%, and 2.14% of the study area, respectively.