EVALUATION OF THE FLOODED AREAS BASED ON HISTORICAL INFORMATION IN EASTERN AEGEAN BASIN OF BULGARIA.

Floods are natural phenomena which cannot be prevented. In order to avoid and reduce the adverse impacts of floods for human health, the environment, cultural heritage and economic activity it is important to provide flood risk management plans. Development of flood risk management plans under Directive 2007/60/EC are elements of integrated river basin management. For the implementation of Directive 2007/60 / EC, Member States need to carry out a preliminary flood risk assessment based on available or readily derivable information. Based on this flood risk assessment, areas are identified where a potential significant flood risk exist or might be considered likely to occur. As part of a preliminary flood risk assessment, it is necessary to describe floods which have occurred in the past and which had significant adverse impacts on the protected categories "Human Health", "Environment", "Cultural Heritage" and "Economic Activities" and where there is a likelihood of recurrence of similar future events. In order to obtain as much information as possible about past floods, different sources of information were used for data collection. The results of the following data collection methods are taken into account: survey of municipalities through a questionnaire on past floods, a list of information of specialized services and departments and evaluation of available materials from literature sources, websites, scientific articles and monographs. After processing, analysing and evaluating the information provided by the various sources, it was found that, for the Eastern Aegean Basin, the main reason for the floods is intense, prolonged rainfall. Another type of floods, common for the basin, is flash floods resulting from intensive (up to 6 hours) rainfall. A small part of the documented floods (three) are as result of sewage overflow. Criteria for the number of affected inhabitants and material damages in the settlements, infrastructure and agriculture are applied. As a result of the analysis and evaluation of the information, 23 sensitive areas have been identified in the region. When identifying potential flood risk areas based on the provided information, there is a risk of missing such areas for which insufficient or complete historical information has been collected. To approximate these areas, an approach with the introduction of a criterion for horizontal distance from the river bed was used. 1D hydraulic modeling and GIS were used to determine the flooded areas in the defined areas at risk in terms of future flood risk. [ABSTRACT FROM AUTHOR]