PDF · Útgáfa VÍ 2012-013 / 4812 — október 2012

Evaluati­on of two delineati­on methods for regi­onal flood frequ­ency analys­is in nort­hern Iceland (skýrsla v. verk­efnis­ins: Mat á flóða­tíðni á ómæld­um vatna­svæð­um)

The goal of the study is to present a regional flood frequency analysis for estimating flood return periods at ungauged and poorly gauged catchments. This information is usually required for the design and management of structures such as bridges, dams and reservoirs. The method involves two major steps, i) the delineation of a set of hydrologically homogenous watersheds with respect to extreme flood statistics, which constitute a "region" and ii) a regional estimation method which transfers the regional flood frequency distribution calculated with streamflow data from the gauged sites, to ungauged or poorly gauged sites, after proper rescaling. In a previous study, geographic regions were arbitrarily defined. Two objective regionalisation techniques are now evaluated for delineating automatically homogenous regions, namely a hierarchical clustering approach and the so-called region of influence approach. The results indicate that the two objective delineation techniques look promising and should be used rather than a geographic delineation as they allow for similar of better results in a rational and more objective manner.