Hydrological criteria to assess changes of flow dynamic in urban impacted catchments

In this study the hydrological assessment criteria flow acceleration, peak discharge and discharge dosage are determined with the focus to assess the quantitative impact on urban rivers. Dependencies of these hydrological parameters are studied within comprehensive statistical analyses with long-term data sets. The hydrological parameters were compared on impacted and un-impacted sites. The influence of land use, influences of discharge data resolution and scale dependencies respectively were investigated. Additionally, probability analyses and calculations of recurrence intervals were conducted for all three parameters. Using those three, sensitive hydrological parameters a hydrological approach is given, which considers the natural hydrograph as target value for a hydrological assessment and captures the whole spectrum of possible changes of the flood hydrograph. Furthermore, the suggested parameters are easily to determine from discharge time series and hence, widely available for management decisions. The study is a contribution for an improved implementation of hydrological assessment indices and capturing flow dynamic variability additionally to qualitative aspects within an ecologically meaningful assessment according to the EU Water Framework Directive.