Hydrologic Scaling of Peak Flows: Implications of Runoff Production Mechanism and Rainfall on the Ungaged Basin Problem

We analyze runoff data from the semi-humid 21.2 sq. km Goodwin Creek Experimental Watershed (GCEW) in northern Mississippi to examine watershed response over a range of scales. Runoff is monitored at the GCEW outlet and in 13 sub-catchments ranging in area from 0.06 to 17.6 sq. km. Previous data-based studies have shown that simple scaling theory fails to describe scaling of flood quantiles in large watersheds, and that there is a fundamental change in scaling behavior in semi-humid watersheds at an area of approximately 100 sq. km. We find that flood quantiles in nearly all sub-basins in the GCEW are self-similar as described by simple scaling theory. The primary reasons why flood quantiles are self-similar on Goodwin Creek are: precipitation is relatively uniform over the basin; peak discharges in smaller catchments are highly correlated with rainfall rates; nearly the entire watershed regularly contributes to runoff; and, the groundwater table plays little role in runoff production. These characteristics are common with runoff from urbanized areas. Therefore, we think it is possible that flood quantiles in urbanized catchments will follow simple scaling.