Flood estimation



In most general terms, there are two alternative ways to estimate design floods and to relate them to some probability (frequency) of occurrence:

  • statistical analysis of observed stream flow data and
  • rainfall-runoff modelling.

Statistical analysis of observed flows

Statistical analysis of observed flows is the basic approach for estimation of flood-frequency relationship when adequate data on observed flows are available. If only a short record of streamflow is available, it is sometimes possible to establish a regional relationship with flows from neighbouring stations and to use such relationship to extend the existing short record in order to perform statistical analysis.

Application of flood frequency analysis is limited to gauged catchments, i.e. to gauged stream profiles. When flow rates of certain probability of occurrence are required at ungauged sites or along a stream (e.g. for flood zone mapping), other methods are needed for flood estimation.

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Flood modelling






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