Design floods for all of Canada: Fid-Bau Portal

Design floods for all of Canada

Faulkner, Duncan

Preliminary design flood flows have been derived for 24,000 locations throughout Canada on rivers with catchments larger than 400 km 2 . In the absence of any published consistent method for flood estimation covering Canada, a flood frequency analysis of instantaneous and daily annual maximum flows at 1664 gauging stations has been regionalized using geostatistical methods. The methodology accounts, in a generalized way, for unusual catchments including arid areas in the Prairie Provinces, the influence of extensive lakes, and (implicitly) for the effects of snowmelt. It does not attempt to represent other more local effects such as flow regulation and diversion. Cross-validation has shown that the results exhibit little bias and at half of all locations the predicted results are within ± 25% of those calculated from the flood peak data, for floods with annual exceedance probabilities of both 1 in 2 and 1 in 20. This broad-scale analysis, which was performed as part of a flood mapping study, helps to pave the way for the development of a unified procedure for flood frequency analysis across Canada, which forms part of the FloodNet research initiative.