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How does the recent
deluge of rain to the Chesapeake Bay watershed compare to the
historic rains and flooding produced by Hurricane Agnes in
1972? In 1972, Agnes was preceded by an unusually wet winter and spring since the ground was already saturated by up to 6 inches of rain, which produced almost immediate flooding. An average of 5 inches of rain or greater were observed watershed-wide, with one-third of the watershed recording 12 inches of rain, and some sites receiving 18 inches over three days in late June 1972. The peak average daily flows during Agnes were 1,130,000 cubic feet/second (cfs) for the Susquehanna River at the Conowingo Dam.
Both events resulted in flooding, destruction of property and unfortunately a number of storm-related deaths, yet these two storm systems produced two very different flooding events. DNR is supplementing its extensive water monitoring network with additional cruises, as well as working with its other partners to monitor the impacts of the storm flood on water quality and aquatic resources in the Bay. Periodic updates will be posted on our Eyes on the Bay website. For more information:
Impacts of June 2006 Extreme Rainfall
Photograph of spectacular
eye and eye wall of a hurricane taken from NOAA P-3 Chart of 2006 Water Year, courtesy of USGS |
The rains of June 24-28, 2006 were just as impressive as Agnes but
were preceded by quite dry periods. Much of the Chesapeake watershed
received rains in excess of 8 inches and isolated regions in the
Bush, Potomac, Susquehanna and mid-Eastern Shore watersheds received
12-16 inches of rain. The June 2006 event produced a peak flow at
Conowingo Dam of 451,000 cfs – well below the historic levels
associated with Agnes.