A FLOOD CLIMATOLOGY OF THE LOWER ROANOKE RIVER BASIN IN NORTH CAROLINA

Abstract

Flooding processes in the lower Roanoke River Basin (RRB) exert a strong control on the distribution of forest-community types and geomorphic landforms across the floodplain. Since the early 1950s, the flow of the river has become regulated as a series of dams have been built upstream of the lower RRB. As a consequence, the variability of the discharge has been reduced dramatically; extended periods of low-magnitude flooding now replace the transient high-magnitude floods that characterized the unregulated regime. In this study, regression analysis is used to model long-term trends in the unregulated flow regime (i.e., no dams upstream). Comparisons of the observed flows before damming with the predicted flows after damming (i.e., no flow regulation) provide estimates of flow alterations resulting from climate change. By comparing the modeled flows with observed flows after damming, the impacts of damming on the river are isolated (i.e., climate held constant). The constructed empirical model indicates that the magnitude and frequency of flooding on the unregulated stream has increased dramatically in the spring, but has decreased in the summer. [Key words: Roanoke River, hydroclimatology, river discharge, damming, North Carolina, Virginia.]