Flood modelling and creating flood inundation maps in Borçka district with geographic information systems (GIS) and HEC-RAS software

Floods, one of the most common natural disasters in the world, cause serious economic damage and loss of life. It is one of the natural disasters that cause the most loss of life and property after earthquakes in our country. Almost every year, floods and landslides occur due to meteorological conditions (excessive precipitation) and anthropogenic activities (human activities such as agricultural activities, excessive irrigation and road excavations) throughout the province of Artvin, which is one of the provinces where natural disasters are most common in Turkey. In the Arhavi, Hopa, Kemalpaşa and Borçka districts of Artvin, which receive the most precipitation, natural disasters with meteorological characteristics such as floods and landslides triggered by excessive precipitation are frequently seen, causing loss of life. The main purpose of this study is to carry out flood risk analyzes of Aksu (Deviskel) and İçkale (Cihala) creeks located within the borders of Borçka district of Artvin province. The ultimate goal of the study is to determine the flood spread maps of the aforementioned streams. The maximum return periods (Q50, Q100, Q500 and Q1000) and the Manning roughness coefficients of the streams used in the study were obtained from the 26th Regional Directorate of SHW in Artvin. The spatial data required to produce the Digital Elevation Model (DEM) of the study area (1/1000 scale current maps) were obtained from Borçka Municipality. In the modeling and analysis phase; one and two dimensional flood models were made using DEM, flood flow rates, manning roughness values and base flows. As a result of these models, flood water surface profiles and flood spreads were produced. At the end of the study, it was determined that 50 buildings and outbuildings around İçkale Stream, 211 buildings and outbuildings around Deviskel Stream, 105.591 m² around İçkale Stream and 90.984 m² around Deviskel Stream could be affected by floods at Q1000 recurrence flow rate. It is aimed that the maps obtained will form a basis for the measures to be taken to prevent possible floods in the study area and/or to minimize their damage.