Estimation of peak flow variability in river basins of Peloponnese through comparative assessment of two widespread methods of flood hydrology

Two methodologies widely used for peak flow estimation, the known as rational and the curve number (CN) – synthetic unit hydrograph combination, are applied to 79 minor (area greater than 100 km2) and 9 major watersheds in Peloponnese area. Both methodologies were applied for three return periods, 20, 50 and 100 years. Four CN values for each watershed were estimated resulting to five peak flow values for each return period for each watershed. The analysis performed indicated that peak flow values for watersheds and subbasins have a big fluctuation range depending on the method applied (the rational method results to maximum values). For example, for return period of 100 years, differences in peak flow values are for most of the watersheds greater than 150% arising to 350%.