We are increasingly confronted with extreme precipitation events and the resulting flood runoffs. The intensity of events increases, the risk of flooding increases. In addition, the conservation of river and floodplain habitats is gaining in importance. For years, the focus has therefore also been on efforts to maintain and expand the natural environment. However, the main objective remains the protection of life and limb against the effects of floods.
The demands on the planning engineer are increasing. The simulation models with which protective measures and their effectiveness can be tested are becoming more demanding.
The hydrological precipitation-runoff models, which provide the input variables for the river models, usually have to be recalculated due to extreme precipitation, and peak discharges and discharge hydrographs have to be redefined.
Hydraulic river model (1D)
To determine the efficiency of water bodies, to calculate flood levels or to show the effect of interventions on the water body, a hydraulic river model is required with which the discharge processes in the water body itself can be simulated taking into account all structures and the existing discharge cross-sections. In the 1D model (Manning Strickler/Darcy-Weisbach), the description of the water body/construction is based on cross profiles. Input variables for the river model are flood peak values.
Hydraulic river model (2D)
Transient calculations are necessary for complex flow conditions and expected retention effects. Especially with strong deviations of the flow direction from the main flow direction, e.g. with protrusions, a 2D-HN model is unavoidable. The use of 1D models is not appropriate in this case.
The use of a 2D HN model requires a detailed description of the existing water geometry (DGM). Input variables of the hydraulic river model are calculated flood hydrographs from the hydrological model or from flood regionalization, which can be applied at the corresponding points along the river. Alternatively, the flow area can also be irrigated. This is particularly useful for the investigation of flow paths in outdoor areas.