Hydrology of floods

Methodology

Mathematical models describe the water cycle considering the most important or relevant physical processes in the nature. The processes over the see surface sometimes are not considered. Furthermore, processes like vapour advection or condensation are also excluded. Those phenomena are meteorological and their simulation in Hydrology is not of great importance.

Important for the simulation is the temporal and plane distribution of the precipitation over the surface. This information is provided by the weather service or any other meteorological institution.

According to the hydrological cycle each kind of hydrological simulation has to consider more or less all input parameter named below:

  • Precipitation
  • Interception
  • Evapotranspiration
  • Snow-Hydrological processes
  • Soil Moisture Regime
  • Groundwater

To model the runoff formation, it is considered the transformation of the effective precipitation of a catchment area into a discharge hydrograph at the outlet node of this catchment area. For the calculation of the runoff formation, the so called hydrologic model approaches dominates. It assumes that the discharge concentration can be decomposed into translation and retention process, where both of them can be linearly superposed.

Applying the translation model, it is possible to describe time delay of the runoff (discharge) streamlines in the water network and subcatchments. Lines of the same translation time, that correspond to the flow duration of a water particle from one point of the catchment area to the outlet node is referred to as isochrones.

On the other hand, the discharge also depends on the retention characteristics. Thus, the discharge concentration is also influenced by the storage capacity of the catchment and not only by the translation process. The retention capacity depends on the soil type, vegetation cover and the slope of the terrain. It particularly influences the shape of the rising limb of hydrograph.


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Module
Flood modelling
Source

TUHH

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