PDF · Útgáfa VÍ 2012-005 / 4812 — júní 2012

Rann­sókn­ir á flóð­um íslenskra vatns­falla – Estimat­ing the flood frequ­ency distri­buti­on for ungauged catch­ments using an index flood procedure. Applicati­on to ten catch­ments in Nort­hern Iceland

The goal of this study is to develop an objective methodology for estimating design floods, i.e. the flood peak discharge with return period T, at poorly gauged and ungauged river catchments in Iceland. This is done by scaling a regional flood frequency distribution by the so-called index flood of the catchment. The regional flood frequency distribution is a dimensionless probability distribution function (PDF) estimated by pooling together the individual flood frequency distributions of a group of homogenous gauged catchments. The index flood is defined as the mean annual maximum flood peak discharge. For gauged catchments, the index flood is estimated from the measured streamflow series. For ungauged catchments, it is estimated by linear regression using physiographic and climatic catchment descriptors. The method is evaluated for ten catchments located in the Tröllaskagi region and in the Westfjords using annual maximum instantaneous and daily streamflow series. The results indicate that the method looks promising for the estimation of the T-year flood peak discharge and the associated confidence interval, along river channels, This methodology should be further developed and tested in other regions.