NOAA 03-R450
Contact: Ben Sherman
NOAA News Releases 2003
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Scientists at NOAA’s Chesapeake Bay Office are watching with both care and interest the eminent arrival of Hurricane Isabel in the Chesapeake Bay watershed. Based on forecasts from NOAA’s National Hurricane Center and the region’s saturated soils, the Chesapeake Bay ecosystem could be in for a rough ride. NOAA is an agency of the U.S. Department of Commerce.

Bob Wood, a fisheries specialist with NOAA’s Chesapeake Bay Office, says the storms potential is not good news for those local, state, federal agencies that focus on protecting and restoring the estuary’s natural resources. He points to history as a guide to potential impacts from Isabel and how it could affect Chesapeake Bay restoration efforts and economically important habitats and species such as blue crab and oysters. The lessons come from re-visiting the impact hurricane Agnes had on the Bay as it traveled through the area in June of 1972.

From June 21-23, (1972) Agnes filled rain gauges throughout the watershed as it entered Virginia as a tropical storm, crossed the mouth of Chesapeake Bay and headed into the coastal Atlantic before turning west into New York and finally dissipating in northern Pennsylvania. While other storms like hurricane Camile recorded as much as 28 inches of rainfall in mountainous Nelson County, Virginia (113 Virginian’s killed, 39 missing), Agnes’ impact on the Chesapeake Bay ecosystem was more dramatic because rainfall over all of the Bay’s watershed was very high. On average, over eight inches fell throughout the Bay’s two largest river basins, the Susquehanna and Potomac. Making matters worse, the storm arrived when soils were already saturated by a wet winter and spring.

The similarity to this hurricane season is striking. Because soils throughout the watershed are now nearly saturated, and Isabel is forecast to track through virtually all of the watershed states, it is possible that Chesapeake Bay could be subject to the same type of ecological damage that resulted from Agnes’ passage 31 years ago.

Effects on the plants and animals

Agnes’ passage resulted in a heavy influx of freshwater entering Chesapeake Bay in 1972, resulting in freshwater pushing tidal saltwater down the Bay more than 30 miles farther than normal. This event had its most of damaging effects on plants and animals that live in, on, or attached to the Bay bottom. Strong currents scoured plants and animals from some shorelines and areas of the Bay bottom, massive amounts of sediment (32 million metric tons of dry sediment from the Susquehanna alone) buried others, and excess nutrients degraded water quality, which further impacted the ecosystem’s populations and habitats.

The effects of these stresses on some key plants and animals lasted for years. The worst hit were some key populations and habitats important to both the ecosystem and the regional economy.

  • As much as two-thirds of the submerged aquatic vegetation habitat disappeared in the Bay.
  • In the middle and upper Bay and its rivers, 90% of the soft clams died
  • Oysters suffered massive mortality, nearly all oysters died north of the Bay Bridge.
  • Dissolved oxygen and light penetration were both low through the following summer (1973) as nutrients delivered by the storm kept phytoplankton populations elevated.

Making matters worse, some of these same plants and animals were already in decline due to a combination of declining water quality and overharvesting.

The situation 31 years after Agnes is surprisingly similar. During this wetter than average year, local, state, and federal agencies, many of which are partners in the Chesapeake Bay Program, realize that the same key habitats and animals are stressed by poor water quality and overharvesting. Confronting a rising regional human population and its effects on the Chesapeake Bay, the Bay Program and its partners are facing stiff challenges. Challenges that could be made worse if Isabel’s track and rainfall total’s follow a worst case scenario.

NOAA’s Chesapeake Bay Program functions to represent all NOAA line offices, including National Marine Fisheries Service (NMFS), the Office of Oceanic and Atmospheric Research (OAR), the National Ocean Service (NOS), the National Weather Service (NWS), and the National Environmental Satellite, Data, and Information Service (NESDIS), and to provide a clear focal point within NOAA for Chesapeake Bay initiatives, involve all relevant NOAA entities in Bay restoration efforts, manage peer-reviewed NOAA-funded research, and to strengthen NOAA’s interactions with Chesapeake Bay partners.

NOAA is dedicated to enhancing economic security and national safety through the prediction and research of weather and climate-related events and providing environmental stewardship of the nation’s coastal and marine resources. NOAA is part of the U.S. Department of Commerce.

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Hurricane Isabel’s forecast track: