Extraction of potential debris source areas by logistic regression technique: a case study from Barla, Besparmak and Kapi mountains (NW Taurids, Turkey)

Debris flow is one of the most destructive mass movements. Sometimes regional debris flow susceptibility or hazard assessments can be more difficult than the other mass movements. Determination of debris accumulation zones and debris source areas, which is one of the most crucial stages in debris flow investigations, can be too difficult because of morphological restrictions. The main goal of the present study is to extract debris source areas by logistic regression analyses based on the data from the slopes of the Barla, Besparmak and Kapi Mountains in the SW part of the Taurids Mountain belt of Turkey, where formation of debris material are clearly evident and common. In this study, in order to achieve this goal, extensive field observations to identify the areal extent of debris source areas and debris material, air-photo studies to determine the debris source areas and also desk studies including Geographical Information System (GIS) applications and statistical assessments were performed. To justify the training data used in logistic regression analyses as representative, a random sampling procedure was applied. By using the results of the logistic regression analysis, the debris source area probability map of the region is produced. However, according to the field experiences of the authors, the produced map yielded over-predicted results. The main source of the over-prediction is structural relation between the bedding planes and slope aspects on the basis of the field observations, for the generation of debris, the dip of the bedding planes must be taken into consideration regarding the slope face. In order to eliminate this problem, in this study, an approach has been developed using probability distribution of the aspect values. With the application of structural adjustment, the final adjusted debris source area probability map is obtained for the study area. The field observations revealed that the actual debris source areas in the field coincide with the areas having high probability values on this final map.