Modeling of flood inundation areas in Denizli province Serinhisar district center with geographical information systems and HEC-RAS package program

Floods stand among the significant natural disasters causing loss of life and property. The primary aim of this study is to assess the flood risk of settlements and determine measures to combat this risk using geographic information systems and hydraulic modeling. For this purpose, Serinhisar district center was chosen as the study area. In this thesis, flood risk analysis was conducted considering flood discharges with return periods of Q25, Q50, Q100, Q200, and Q500. The hydraulic modeling method "Hydraulic Engineering Center's River Analysis System" 2D model was utilized to determine both the verification of existing flood channel dimensions at the mouth of the Çaykesiği Stream and the spread of floods from the Kavaklar and Hamamcıçeşmesi streams within the city. In this context, with the support of the Denizli Metropolitan Municipality Water and Sewerage Administration (DESKİ), a Digital Elevation Model of Serinhisar District Center was produced using a 50 cm resolution unmanned aerial vehicle (Drone). Then, rainfall data were obtained from the largest observed rainfall events (mm) at standard intervals from the Ajıpayam Meteorology Station. The results of 64 different statistical distributions were determined using Easyfit Software. Among these distributions, the Gamma*3P distribution showed suitability. Accordingly, potential floods originating from streams in Serinhisar district center were examined in detail. Then, using the McMath and Mockus method, maximum flood discharges with return periods of Q25, Q50, Q100, Q200, and Q500 were calculated, and depth and water spread areas were determined for each scenario. As a result of the flood analysis, it was determined that flood spreading heights in Serinhisar Center range from 0.24 m to approximately 4.5 m, and the water spread areas according to flood return periods are 254,228.00 m², 267,368.00 m², 278,191.00 m², 281,043.00 m² and 301,815.00 m² respectively. According to these results, hundreds of residences and businesses are at risk of being submerged, and agricultural areas in the lower basin of the Denizli-Antalya road and Serinhisar Center are significantly affected by floods. Additionally, flood risk maps were created for Serinhisar Center.