ANNAPOLIS – As Hurricane Isabel advances toward the eastern seaboard, officials fear flooding will wreak havoc on the Chesapeake Bay.
Extended rain could flood the brackish bay with fresh water and fill it with soil runoff, making its water fresh, cloudy and uninhabitable to many species. Above-normal rainfall this year makes soil runoff likely.
“This year has been constant rain, constant overflow of fresh water,” said Chris Judy of Maryland’s Department of Natural Resources. “And now we get a hurricane.”
Increased soil and freshwater runoff threaten underwater grasses that cannot survive in cloudy water and oysters that need salt water to live. Oysters are also threatened by soil runoff because they feed by filtering water.
“The sediment is just going to choke them,” said Mike Fritz, a coordinator for the Chesapeake Bay Program.
The threat to oysters comes at a perilous time for the species.
“The oyster population is at an all-time record low,” Judy said.
Last season’s oyster harvest amounted to only 53,000 bushels, the lowest catch since Maryland began keeping records in the 1870s. Maryland once produced as many as two million bushels a year.
Underwater grasses provide habitat for fish and migrating birds and generate oxygen needed by many species.
Hurricanes have always meant increased levels of soil and fresh water runoff into the bay, and the extent of Isabel’s damage depends on the amount of rain it brings.
The intensity of rainfall is a “paramount concern,” according to Quentin Banks, spokesman for the Maryland Emergency Management Agency. Because the soil is already saturated “the rainfall has nowhere to go,” Banks said.
Isabel is expected strike the East Coast Thursday. It appears to be headed toward the bay’s watershed, which extends from central New York to southern Virginia.
Damage to the bay from flooding has occurred in the past. In 1972, the problem was Hurricane Agnes.
“Agnes brought an incredible amount of sediment into the bay,” Fritz said. “It took decades to see underwater grasses come back from Agnes.”
A 1976 study indicated Agnes reduced bay grasses by 67 percent.
Flooding struck again in September 1996 when remnants of Hurricane Fran crossed the bay watershed and combined with months of unusually high fresh water flows, causing widespread sediment and freshwater runoff.
Yet Scott Phillips, Chesapeake Bay coordinator of the U.S. Geological Survey, does not think bay destruction from Isabel will reach levels wrought by Agnes.
“If a hurricane is going to hit, it’s better if it hit this time of year rather than June,” Phillips said.
Agnes, which hit in June, was so destructive because it hit just as oysters began spawning and bay grasses began growing.