Disaster Risk Reduction Based on a GIS Case Study of the Čađavica River Watershed

Abstract

Background and Purpose: Although natural hazards cannot be prevented, a better understanding of the processes and scientific methodologies for their prediction can help mitigate their impact. Torrential floods, as one of the consequential forms of the existing erosion processes in synergy with extremely high precipitation, are the most frequent natural hazard at the regional level, which was confirmed by the catastrophic events in May 2014 when huge territories of Serbia, Bosnia and Herzegovina and Croatia were flood-struck. The basic input data for the design of protective structures in torrential beds and watershed slopes are the values of the maximal discharge, area sediment yields, and sediment transport. The calculation of these values requires a careful approach in accordance with the characteristics of torrential watersheds, such as the steepness of slopes and beds in torrential watersheds, intensive erosion processes, favorable conditions for fast runoff formation and the transport of huge quantities of sediment. Materials and Methods: The calculations of maximal discharges, area sediment yields, and sediment transport in the experimental watershed of the Čađavica River were based on using two different spatial resolutions of digital elevations models (DEMs) – 20 m resolution DEM, with land use determined from aerial photo images, and the 90 m resolution DEM, with land use determined on the basis of the CORINE database. The computation of maximal discharges was performed by applying a method that combined synthetic unit hydrograph (maximum ordinate of unit runoff qmax) and Soil Conservation Service methodologies (deriving effective rainfall Pe from total precipitation Pb). The computation was performed for AMC III (Antecedent Moisture Conditions III – high content of water in the soil and significantly reduced infiltration capacity). The computations of maximal discharges were done taking into account the regional analysis of lag time, internal daily distribution of precipitation and classification of soil hydrologic groups (for CN – runoff curve number determination). Area sediment yields and the intensity of erosion processes were estimated on the basis of the “Erosion Potential Method”. Results and Conclusions: The selected methodology was performed using different input data related to the DEM resolution. The results were illustrated using cartographic and numerical data. Information on relief conditions is a vital parameter for calculating the elements of the environmental conditions through the elements of maximal discharge, area sediment yields and sediment transport. The higher precision of input data of DEM provides a more precise spatial identification and a quantitative estimation of the endangered sites.

Keywords

• torrential floods
• erosion
• DEM resolution
• land use
• maximal discharge
• area sediment yield