Summary

Because of the risk to human life, the adequacy of a spillway of a dam upstream of a population center is judged with the PMF, which is the result of the PMP. The PMP is an estimated limiting value event: the largest magnitude possible for a hydrologic event at a given location, based upon the best available hydrologic information.

HEC-HMS can be used to compute the PMF, using PMP depths as input for the hypothetical storm. Common loss and transform methods can be used, but adjustments to the parameters may be required to represent the worst-case condition. Likewise, dam and spillway performance can be simulated with the reservoir model included in HEC-HMS. For that, the analyst must derive and specify functions that describe how the reservoir will perform.