Computation of backwater effects in surface waters of lowland catchments including control structures – an efficient and re-usable method implemented in the hydrological open-source model Kalypso-NA (4.0)

Abstract. Backwater effects in surface water streams and on adjacent lowland areas caused by mostly complex drainage flow control structures are not directly computed with hydrological approaches yet. A solution to this weakness modelling is presented article. The developed method enables transfer of discharges into levels calculation backwater volume routing along balancing level slopes. implemented evaluated extends the application models for rainfall–runoff simulations backwater-affected catchments advantages (1) systems tidal lowlands, (2) less effort parameterise river streams, (3) defined input factors driving forces (climate change urbanisation) (4) runtime reduction 1 2 orders magnitude comparison coupled hydrodynamic models. open-source model Kalypso-NA (4.0). Evaluation results show applicability simulating regimes an exemplary catchment (Hamburg, Germany) a system where influenced range about 4 m. proposed applicable answer wide scope management questions, e.g. balances, flood forecasts effectiveness mitigation measures. It re-usable other numerical models, which apply conceptual flood-routing (e.g. Muskingum–Cunge or Kalinin–Miljukov).