Paleohydrologic bounds and low probability floods

摘要

An expeditious way to evaluate the magnitude of low probability floods is to identify and assign ages to geomorphic surfaces adjacent to a stream that serve as limits for the paleostage of large floods over thousands of years. These paleostage limits can then be input into a hydraulic model to calculate the maximum discharge that would not significantly inundate. and therefore significantly modify, a particular geomorphic surface. This maximum discharge, together with age of the surface, forms a conservative limiting bound on flood discharge through time that is input for flood-frequency analysis. These paleohydrologic boudns are not actual floods. but instead they are limits on flood magnitude over a measured time interval. In this way, these bounds represent stages and discharges that have not been exceeded since the geomorphic surface stabilized.