METHODOLOGIES AND APPLICATION Flash flood potential prioritization of sub-basins in an ungauged basin in Turkey using traditional multi-criteria decision-making methods Hu ¨ seyin Akay 1 • Mu ¨ steyde Baduna Koçyig ˘ it 1 Ó Springer-Verlag GmbH Germany, part of Springer Nature 2020 Abstract Morphometric analysis of watersheds based on morphometric parameters is the most widely accepted method for watershed prioritization. However, traditional methods adopted for prioritization of sub-basins lack a standard classifi- cation of the morphometric parameters and ranges of their values. So, in this study several multi-criteria decision-making (MCDM) methods and a number of traditional methods are used for watershed prioritization regarding the flash flood potential of the sub-basins. Akc ¸ay, a small ungauged basin in Turkey, was chosen as the study area, and 12 morphometric parameters were determined for the basin. The geomorphological instantaneous unit hydrograph concept coupled with Monte Carlo analysis was used to estimate the flood yield of the basin due to the lack of flow data. Kendall tau and Spearman correlation coefficient tests and receiver operating characteristics analysis were performed to validate the results of the traditional methods and the MCDM approaches for prioritization of the sub-basins. Results showed that the AHP method could well predict the sub-basins with higher flood potential, while the methodology adopted in the study to determine the criteria weights obtained from ANP method in MCDM improved the prediction capability of those approaches, especially VIKOR. The initial values of criteria weights were determined to be effective on the predictions and sensitivity analysis. When the results of traditional methods and MCDM approaches were compared, the MCDM approaches were found to give improved results. This study showed that MCDM approaches can be used to provide an efficient management of basins regarding conservation of water resources and soil. Keywords Multi-criteria decision-making methods Á Morphometric parameters Á Prioritization Á Flash flood potential Á Western Black Sea Basin 1 Introduction Some extreme weather conditions such as the occurrences of heavy rainfall, floods, drought, heatwaves and hurri- canes have increased in recent decades all over the world. Some research has shown that the appearance of these events is the outcome of potential changes in climate and the impact of climate change on floods is especially sig- nificant (Frei et al. 2000; Milly et al. 2002; van Aalst 2006). So, watershed management faces a substantial challenge from those flash floods. Moreover, management challenges such as the mitigation of flood hazards, instal- lation of control structures and urbanization stress on the environment demand a thorough knowledge of the mag- nitude and frequency of flooding events and their change through time (Knuepfer and Montz 2008). Hence, water- shed prioritization which is based on grading of different watersheds of a basin has become an important means for watershed management. Moreover, it might even become more crucial for ungauged basins where no or scarce flow data are available and the watershed is prone to flash floods. In the literature, different methods have been developed for prioritization of watersheds among which morphometric analysis is accepted to be the best approach (Sukristiyanti et al. 2018). Morphometric analysis depends on grading of various morphometric parameters of water- shed. However, despite many approaches and researches Communicated by V. Loia. & Hu ¨seyin Akay akayhsyn@gmail.com Mu ¨steyde Baduna Koc ¸yig ˘it musteydebaduna@gmail.com 1 Civil Engineering Department, Gazi University, 06570 Maltepe, Ankara, Turkey 123 Soft Computing https://doi.org/10.1007/s00500-020-04792-0