Flood Risk Assessment in Geographic Information Systems Environment Using Analytical Hierarchy Process: İzmir Meles Stream Catchment Case

Project no. 27382 · Status: Kapanmış · 2023

Summary

Sudden and heavy rains and floods seen in the city of Izmir in the distant and recent past, especially in the winter months, due to climatic conditions and topographic features, as well as inadequate infrastructure, urban sprawl, the replacement of urban permeable surfaces with impermeable surfaces, and the deterioration of the flow regime as a result of the alteration of stream beds with anthropogenic effects. and cause flood disasters. The location of residential areas on flood and floodplains within the city causes loss of life and property in these disasters. Therefore, it is important to identify risky areas in order to eliminate/minimize the losses caused by disasters and to combat possible danger by developing solution proposals on a planning scale. The aim of the project is to analyze the flood risk of the Meles Stream Basin, which is a micro-basin located in the city of Izmir and stands out with its urban character, and to determine the areas at risk and map them spatially. Analyzing the flood risk in the basin located in the city center and characterized by residential and industrial land uses will be effective in determining the areas to take precautions by determining the impact area of a potential flood in the relevant residential and industrial areas. Meles Stream originates from the Adnan Menderes Airport area, flows in the north direction and flows into the Gulf of Izmir. It is the water system with the longest route located in the city center. Settlement, trade and industrial areas have developed along the highway axis that divides the Meles Stream Basin into two in the north-south direction. On the other hand, there is also a highway axis that divides the basin into two in the east-west direction. This axis serves as a threshold between the natural vegetation spread in the south of the basin and the built areas spread in the north. Meles Stream basin has gone through dynamic natural and cultural processes from past to present. Although it has significantly lost its natural characteristics and ecological function by being taken into the canal today, the vegetation spread especially in the south of the basin, in other words in the lands close to the upstream of the stream, is promising regarding the resilience of the basin against floods. On the other hand, towards the downstream of the basin, close to the Gulf, the construction is quite dense and densely textured. The loss of life and property resulting from the sudden and heavy rains that the city of Izmir has encountered in recent years requires studies at the scale of landscape planning within the scope of combating floods in the city. Increasing residential, commercial and industrial uses in the basin of the Meles Stream flowing in the city center make the region risky in case of a possible flood event. The subject of the project is to analyze the flood risk through geographical information systems in a micro-basin located within the city and stand out with its urban character, to create a flood propagation map and to determine the areas at risk. It is aimed to reveal the relationship between the land use classes of the risky areas identified within the scope of the study and the topographic, hydrological and socio-cultural characteristics of these areas. In this sense, the project involves mapping the flood risk of the Meles Stream in the city of Izmir and visualizing its risk potential. The hypothesis of the research; The flood risk areas within the borders of the Meles Stream Basin include residential, commercial and industrial areas with intensive use, located on the north-south axis of the city center. The city of Izmir has been experiencing sudden and heavy rains in recent years, resulting in loss of life and property. Settlement, commercial and industrial uses in the basin of Meles Stream, which flows in the city center, are spread in the sub-basin where the slope is low. This makes this region risky in case of a possible flood disaster. The hypothesis of the research; The flood risk areas within the borders of the Meles Stream Basin include residential, commercial and industrial areas with intensive use, located on the north-south axis of the city center. This study aims to calculate and map this risk. If the research results are shared, it will be possible for local administrators to make risky areas resistant to floods before a possible disaster occurs. Although the Meles Stream Basin has been the subject of many studies before (Kılıçaslan and Özkan, 2006; Özeren, 2012; Özeren and Kaplan, 2013; İzmir Metropolitan Municipality, 2020; Özer and Şahin, 2021), there has been no risk mapping on flood risk in the basin before. It has not been done. It is anticipated that this gap in the literature will be closed with this study. Within the scope of this study, in order to determine and map the flood risk of the Meles Stream Basin, 10 evaluation criteria were determined by examining the unique natural and cultural/anthropogenic features of the basin. The determined evaluation criteria will be weighted using the Analytic Hierarchy Process (AHP) method in terms of their potential to affect floods, taking into account the characteristics of the area. Potential flood areas will be mapped spatially by overlaying the parameters with the Weighted Overlay method according to their impact weights.

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