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In the present study, 43 watersheds in Serbia and Bulgaria are taken for the morphometric analysis using digital elevation model in the environment of geographical information system. Statistical analysis, including correlation, regression and factor analysis is conducted with the following results and conclusions: (1) as evidenced in the correlation matrix, there is a high correlation between maximal discharges and watershed area, primarily and watershed length, secondarily; (2) the high correlation is found between independent variables watershed area and watershed length, as well as Melton index and relief ratio; (3) the multiple linear regression model encompassing all seven independent variables is obtaind with R squared of 70,99, indicating that the model as fitted to that extent explains the variability in maximal discharge, and adjusted R squared of 0,65. An additional multiple regression analysis is done excluding the watershed area, due to a high starting impact on the dependent variable. In this case, a multiple regression linear model is obtained with R squared=60,116 and adjusted R squared=0,53468, leading to the conclusion that the excluded parameter has a high influence which is also confirmed by the results in correlation matrix; (4) according to the rotated component matrix in principal component analysis, first component is mostly influenced by the relief ratio, Melton index and watershed length, while the second component is determined by parameters of relief characteristics, slope >25ᵒ and watershed relief. Having regard to the results of correlation and factor analyses the watersheds are prioritized on the basis of the morphometric parameters with a purpose to indicate the watersheds with the high priority for implementation of measures reducing the flood risks. Though morphometric study itself is not sufficient to explain extensively the occurrence of maximal discharges in the events of demolishing torrential floods, morphometric analysis may meaningfully contribute to the flood risk assessment.

<p><strong>Abstract.</strong> Natural hazards are existence of natural components and processes, which create a situation that could negatively affect people, the economy and the environment. In this concern, they are associated with the probability of negative impacts and they are considered as limiting factors for people's lives and activities. Rising public awareness about natural hazards could improve the quality of life, save financial resources and even save lives. Methodological issues of complex analysis of multiple natural hazards in geographic information system (GIS) environment are presented in the current paper on the example of floods and landslide assessment. The complicated nature of natural hazards and the interrelations between natural components require a complex analysis of natural hazard factors and an integrated assessment taking into account all aspects of different hazards as well as the overall hazard resulting from a probable simultaneous occurrence of several adverse natural phenomena. A special attention is given to the data as one of the most important component of the analysis. Different data formats and particularities of spatial data interpretation in GIS environment are considered. Having regard the nature of the data and the phenomenon being evaluated, different GIS spatial analysis tools (fuzzy overlay, weighted sum, interpolation) are applied together with mathematical analyses. The results of the current research and suggested approach could support decision makers in territorial planning and risk management.</p>

Soil erosion is the most serious soil degradation factor on the territory of Bulgaria. Nearly 66 % of its area have slopes in a range greater than 3°. The predominant hilly-mountainous relief and high slope degrees are prerequisites for development of water erosion. The properties of the topographic surface as a conditioning factor of erosion processes are evaluated in the current study on the example of the Dzhebelska River watershed (Southern Bulgaria). The following morphometric parameters are considered: basin relief, Melton index, slope and stream power index (SPI). Slope length and steepness factor (LS factor) is calculated using the slope degree and specific contributing area. The values vary between 0 and 43.36. The results of the analysis of the morphometric parameters indicate high erosion susceptibility in the upper and the middle part of the watershed but active erosion can be observed too in the low part of the watershed, where first order streams (Strahler’s method) flows directly to the river of fifth order. The current study is done in GIS environment on the base of 12 m digital elevation model.