REGIONAL FLOOD FREQUENCY ANALYSIS IN SOUTHERN ONTARIO USING L-MOMENTS

Annual flood series from unregulated rivers in southern Ontario are examined with a view to testing the efficacy of the generalized extreme value distribution to represent all flood frequency characteristics in the area. Series are characterized by their sample L-moments, the higher orders of which are more reliable than product moments, facilitating both the selection of the appropriate probability distribution and the estimation of its necessary parameters. The generalized extreme value distribution is found to provide a good fit to the diversity of annual flood characteristics found in the area and to furnish a reasonable regional flood frequency distribution. The spatial variations of the derived parameters may be successfully explained in terms of potential geographic and hydrologic controls on precipitation input, flood generating processes (snowmelt or rainfall), and land use