We investigate the links between the drainage density of a river basin andselected flood statistics, namely, mean, standard deviation, coefficient ofvariation and coefficient of skewness of annual maximum series of peak flows.The investigation is carried out through a three-stage analysis. First, anumerical simulation is performed by using a spatially distributedhydrological model in order to highlight how flood statistics change withvarying drainage density. Second, a conceptual hydrological model is used inorder to analytically derive the dependence of flood statistics on drainagedensity. Third, real world data from 44 watersheds located in northern Italywere analysed. The three-level analysis seems to suggest that a criticalvalue of the drainage density exists for which a minimum is attained in boththe coefficient of variation and the absolute value of the skewnesscoefficient. Such minima in the flood statistics correspond to a minimum ofthe flood quantile for a given exceedance probability (i.e., recurrenceinterval). Therefore, the results of this study may provide usefulindications for flood risk assessment in ungauged basins.
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