Spatial and temporal aspects of high streamflow periods within the Danube drainage basin in Bulgaria

Abstract

High flow events are the main prerequisites for floods with negative social and environmental consequences. Their study under uncertain and changing climate gives informative knowledge for further management decisions. This paper seeks to analyze the spatio-temporal parameters of high flow periods within the Danube drainage basin in Bulgaria. Three characteristics of the hazard phenomena: time of occurring, frequency and duration are investigated. The analysis is based on daily discharge data collected from 20 gauging stations for the period 2000–2005. The surplus water quantities are identified by the Threshold level method using fixed values – Q25 and Q5, derived from the flow duration curve. Results show a concentration of the high flow periods during the spring hydrological season, with an average duration up to six weeks. The calculations establish positive correlations between the duration of high flow, the altitude of catchments, and the density of drainage network. The resulting information can serve as a support for the development of preliminary flood risk assessments in the Danube River Basin