How Did Sandy Affect the Chesapeake?

The center of Hurricane/Superstorm Sandy made landfall the evening of October 29 near Atlantic City, New Jersey, but significant effects were felt across the Chesapeake Bay watershed and beyond. While NOAA scientists are analyzing information and planning more in-depth research on Sandy’s effects on the Bay and its living resources, initial data are available.

NOAA Chesapeake Bay Interpretive Buoy System observing platforms tracked data at 10 locations during the storm. The peak wind observed was at the Potomac/Point Lookout buoy—52.5 knots (60.4 miles/hour) from the north at 6:30 p.m. on October 29. The maximum wave height was at the First Landing buoy—14.9 feet at 7:00 a.m. on October 29. Below is a map with maximum wind speeds and wave heights at each location (note: First Landing windspeed stopped reporting as of 7:10 a.m. on October 28, likely due to impact with 15-foot breaking waves). CBIBS buoys track wind speed at roughly 14 feet off the water; wind speeds recorded by other observing stations may have instruments that are located at higher points (e.g., the sensor at Thomas Point Light, which recorded a gust to 66.9 miles/hour (29.9 meters/second, is 59 feet off the water).

While parts of New Jersey, New York, and the southern New England coast dealt with crippling storm surge, for the most part, the Chesapeake Bay avoided surge-related flooding, though some coastal flooding was reported. Because Sandy made landfall northeast of the Bay and then moved north-northwest, the Chesapeake experienced winds primarily out of the north and northeast during the height of the storm. Thus, there was no big “push” of water up the Bay associated with landfall.

But some areas along the Bay experienced surge-type flooding on Tuesday, October 30, especially during high tides, because by then the winds had shifted around to the south. NOAA monitors water levels at 16 locations in the Bay; they reported storm surges of 2 to 4 feet on top of an already high astronomical tide (full moon was the afternoon of October 29). The storm surge, which was highest in the Hampton Roads area, was approximately half of that seen during Hurricane Isabel in 2003. Isabel moved west of the Bay as it moved north, and its counterclockwise motion pushed water up the Bay.

But high rainfall around the watershed—including a storm-high 12.55 inches at Easton, Maryland, on the Eastern Shore—also brought flooding to some parts of the Bay. Notably, the rainfall is significantly raising water levels on the Potomac River and some of its tributaries, including the Monocacy River. The map below shows multisensor rain totals as tracked by rain gauges and radar.

Precipitation in the Chesapeake Bay watershed during Superstorm Sandy

The NOAA National Weather Service’s Middle Atlantic River Forecast Center continues to track and forecast flooding, including peak levels, in the Chesapeake Bay watershed. Much of the rainfall is still upstream from the Bay, working its way down through the river systems.

Rainfall from Sandy is affecting different parts of the Chesapeake Bay watershed than did 2011’s Irene and Lee rainfalls, which brought tremendous rainfall to the Susquehanna River watershed, especially from Lee. In the aftermath of those storms, rainfall increased flow of the Susquehanna River so much that the Conowingo Dam—located in the lower Susquehanna River near where it meets the Chesapeake Bay—had to release major amounts of water, which sent an accompanying sediment plume into the Bay.

NOAA scientists are working with scientists from partner agencies including the U.S. Geological Survey and Environmental Protection Agency to analyze how Sandy is affecting the Bay. For example, once skies clear, images from NOAA satellites will help scientists explore how the Bay is changing, including surface water temperatures and sediment levels. New satellite images will be compared with images from before the storm hit.

Scientists and experts will use this analysis to explore how changes may affect living resources in the Bay—for example, will the freshwater from the rainfall hurt or help oysters? Will declining water temperatures encourage blue crabs to move within the Bay or influence striped bass? Because it’s so late in the season, will underwater grasses be affected at all? NCBO will post more information on this as it becomes available.