Checking Flood Frequency Curves Using Rainfall Data

There is no agreement on the best way to develop flood frequency curves and synthesize runoff peak flow rate data, and no precise procedure which applies to all cases of flood frequency statistics. Consequently it is prudent to check the data to see whether a given flood frequency curve is apppopriate. One such check is a statistical evaluation of the rainfall depth-duration frequency data corresponding to the critical duration of the catchment as associated with each annual peak flow rate. A chi-squared test applied to this data is useful in checking how ``rare'' or ``probable'' the rainfall data are with respect to the model frequency, thereby checking how probable is the flood frequency curve. It is interesting that such a check is sensitive to the precise definition chosen for the ``T-year event.''