Increasing frequency of intense rainfall events and flood damages in the northeastern U.S. suggest a corresponding increased need for a quantitative understanding of the drivers of flash-flooding, and improved flash flood warning systems. Although a number of metrics of stream flashiness are available, the effectiveness or sensitivity of the various measures has not been well established. We investigate different measures of stream flashiness as a function of urbanization and various watershed characteristics, including some novel metrics related to event hydrograph shape. We focus on the Mid-Atlantic region where heavy precipitation and large flood events have increased in recent decades, and urbanization over the past century has transformed flow regimes of many streams. The dataset includes streams with a continuous flow record from 2010 to present, limited reservoir storage and flow regulation, and drainage area less than 250 sq km. We show that numerous characteristics impact watershed flashiness well beyond imperviousness. We also find that the influencing characteristics differ between small versus large drainage areas and between rural, suburban, and urban environments. Further work will focus on developing a multivariate model of flash-flood susceptibility that can inform current operational practice.
.jpg "Rachel F. Hurley (she/her/hers) photo")
.jpg "David Brandes, A.M.ASCE photo")
