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

McKerchar, A. I.; PEARSON, G. P.

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

1990

McKerchar, A. I. | PEARSON, G. P.

The two-parameter EV1 distribution adequately describes New Zealand's flood series. Contour maps of [Qbar]/A(0.8) and Q(100)[Qbar] are presented, where [Qbar] is the mean annual flood, A is the basin area and Q(100) 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 Q(T) with specified annual exceedance probability (1/T) can be obtained using map estimates of [Qbar]/A0.8 and Q(100)[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.

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