Hollis, G. 1975. The Effect of Urbanization on Floods of Different Recurrence Intervals. Water Resources Research. American Geophysical Union, London, England. Volume 11, Number 3. Page 431

flooding, hydrology, impacts, impervious, stream

The results of previously published studies are synthesized to show the general relationship between the increase in flood flows following urbanization and the percentage of the basin paved and the flood recurrence interval. In general, (1) floods with a return period of a year or longer are not affected by a 5% paving of their catchment, (2) small floods may be increased by 10 times by urbanization, (3) floods with a return period of 100 yr may be doubled in size by a 30% paving of the basin, and (4) the effect of urbanization declines, in relative terms, as flood recurrence intervals increase.