Maps of flood statistics for regional flood frequency analysis in New Zealand

Open Access
Publisher Website
Google Scholar
Abstract
The two-parameter EV1 distribution adequately describes New Zealand's flood series. Contour maps of [Qbar]/A0.8 and Q100[Qbar] are presented, where [Qbar] is the mean annual flood, A is the basin area and Q100 is the 1% annual exceedance probability flood. The maps are based directly on measured discharge series from a large sample of river recording stations. Thus when basins are ungauged, or have just a short record, an estimate of a design flood QT with specified annual exceedance probability (1/T) can be obtained using map estimates of [Qbar]/A0.8 and Q100[Qbar], without having first to estimate rainfall statistics for the basin, a particularly difficult task in sparsely instrumented mountainous areas. These maps succinctly summarize a great deal of hydrological information and permit improved flood frequency estimates.