Mapping and analysis of river network modification as a factor of flood risk in the Blanice river basin

Abstract

Anthropogenic modifications of river network represent a significant phenomenon that influences runoff conditions in river basins, both under normal water level conditions as well as in the period of hydrological extremes. Modifications of watercourses on various levels influence the speed and timing of floodwave progress as well as the potential to efficiently transform the floodwave in the floodplain and to lessen the extremity of the flood event. The paper presents the methodological framework for analysis of historical and current intensity and nature of man-made modifications of river network. There are presented two essential approaches: First represents the analysis of distance data, e.g. the water management maps, historical maps or aerial imagery. The second approach is based on field mapping of various parameters of river network and floodplain modifications. The presented methodologies are applied on the Blanice river basin that represents the core zone of extreme flood in August 2002 that heavily affected the Central Europe. The GIS analysis of results revealed the spatial differentiation of anthropogenic changes in river basin and their potential importance in the context of the flood risk. The results and the applied methodologies are discussed from the viewpoint of their practical applicability and of limitations in terms of data accuracy, availability and reliability.