Author(s): Stefan Achleitner, Benjamin Kammereck, Bernhard Kohl, Leopold Stepanek, Robert Sitzenfrei
Linked Author(s): Stefan Achleitner
Keywords: Design rainfall, hydrograph superposition, retention basin, torrent hydrology, urban hydrology
Abstract: The design of retention measures in urban sewer systems is well known, but only aspect of the sewer system itself is considered, with regard of the hydraulic design of retention basins. Runoff from urban and natural catchment parts is often considered independent due to the faster response from urbanized areas in many cases. To reduce the peak flows from the urban area at an economically feasible level is the main goal. In general, this argument does not lack logic but is far from being evidenced. Situations, where the urban peak discharge is reduced (which is positive) but as well delayed bear the risk that peak discharges (urban and torrent) superposition to an increased total discharge in the torrent. Purpose of this work is to investigate the dynamic interaction between an urban and torrential catchment. The aim is to test if reducing the urban peak discharge leads to an overall reduction of the peak flow for different situations. Two models describing the rainfall runoff generation from Torrent and Urban catchment parts were coupled and ran sequentially. A systematic variation of spatial rainfall distributions and simulation allowed evaluating the situation in a generalized way. Simulations were made with and without the retention basin installed. Although the urban catchment part, which is retained via the basin was small compared to the overall catchment, a clearly visible increase of peak flows was found in some cases. Combinations of rainfall situation in the different catchment parts led to increased peak discharges were identified. The magnitudes of increases found for this catchment situation were small. Still, for cases with smaller torrential catchments as compared to the urban parts, increases can be more significant. Thus, future steps include the assessment of different catchment configurations
Year: 2017