Investigation of flood and soil liquefaction risks for disaster risk reduction in the construction of water reservoirs

Two water treatment plant project sites in Çambel and Bozalan, which are planned to be constructed in Menemen and Kemalpaşa districts of Izmir until 2030 within the scope of Turkey’s national water plan, were analysed in terms of soil liquefaction and flood risks during earthquakes in this study. In the study, the ’Simplified Method’ was used for soil liquefaction analyses and HEC-RAS-2D software was used for flood modelling. Soil liquefaction risks between 3.5 m–15.5 m for the Çambel water treatment plant project site and between 3.5 m–15.0 m for the Bozalan project site were determined with this study. Therefore, ground reinforcement such as jet grouting or deep soil mixing columns are recommended for both water treatment plant project sites in this study. This study revealed that there are differences in water depth and flow velocity data during flooding between the floodplain modelling results obtained in this study and the national flood management plans and reports of the Turkish government. In the ’Gediz Basin Flood Management Plan’ prepared by the General Directorate of Water Management of the Ministry of Agriculture and Forestry of the Republic of Turkey in 2023, it was determined during the field studies carried out in Çambel and Bozalan settlements that the streams and the Gediz River have a flood risk and it was reported as ’low flood risk’ for these regions. However, national government reports are based on 1D modelling flood analyses, whereas ’high flood risk’ was found for these areas using 2D modelling in this study.