H172-0024
WHAT DO SMALL URBAN WATERSHEDS TELL US ABOUT CLIMATE CHANGE? COUPLED ANALYSES OF TWO DECADES OF URBAN STREAMFLOW AND A 20-YEAR HIGH-RESOLUTION RADAR RAINFALL DATA SET

Tuesday, 15 December 2020
Poster
Andrew J Miller1, Mary Lynn Baeck2, James A Smith3, Molly Margaret Margaret Chaney3 and Touba S Shah4, (1)University of Maryland Baltimore County, Dept. of Geography & Environmental Systems, Baltimore, MD, United States, (2)Princeton University, Department of Civil and Environmental Engineering, Princeton, NJ, United States, (3)Princeton University, Civil and Environmental Engineering, Princeton, NJ, United States, (4)University of Maryland Baltimore County, Dept. of Geography & Environmental Systems, Baltimore, United States
Abstract:
The Baltimore, MD metropolitan area is home to some of the flashiest urban watersheds in the conterminous United States. Rainfall-runoff behavior is typically attributable to patterns of impervious cover and efficiency of storm-drain networks, causing storm hydrographs to mimic the timing and intensity of short-term rainfall fluctuations. Emerging evidence suggests that the urban streamflow signal in some watersheds may now be responding to changes in frequency of intense precipitation associated with climate response to greenhouse warming.

In this presentation we examine spatial and temporal trends from a 20-year 14,000-km2 record of warm-season rainfall derived from Sterling, Virginia WSR-88D radar observations (single polarization from 2000-2012, dual polarization from 2012-2019), with temporal resolution of 15 minutes and spatial resolution of 1 km2. Examination of spatial patterns reveals sharp gradients in frequency and amount of rainfall attributable to high intensity precipitation over distances of 50-100 km. These gradients are not evident from analyses summarized in the NOAA precipitation frequency atlas. We compare these trends with temporal trends in frequency of high flow for a set of small urban watersheds across the Baltimore-Washington metropolitan area, and we explore the dynamics of rainfall-runoff relationships for a series of high-intensity short-duration convective storms and a smaller set of longer-duration extreme storms responsible for flood peaks that are at or above the regional envelope curve.

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