NASA Image Shows Sediment Clouding the Chesapeake Bay

NASA’s Image of the Day today features a satellite image showing storm runoff flowing into the Chesapeake Bay on Sept. 9 after Tropical Storm Lee drenched the area with heavy rains. The ensuing floods from the storm swept up debris, garbage, sewage, farm runoff and mud, carrying all of it down rivers and streams into the bay.

Since records began in 1967, only two other events have carried more fresh water into the bay: Tropical Storm Agnes in 1972 and a snowmelt event in 1996. This year, rain from Tropical Storm Lee has had a far greater impact on the bay than Hurricane Irene.

The muddy influx covers much of the top half of the bay in this image captured by the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Terra satellite on Sept. 13.

After Lee, the bay turned from its normal dark blue to a muddy tan, an indicator that thick sediment clouds the water. Resource managers use images like these along with other satellite data to help gauge the extent of runoff events, said Mark Trice from the Maryland Department of Natural Resources. Satellite data also helps managers confirm readings taken from boats and measuring stations.

The mud and debris is bad for the bay for many reasons. The mud damages grasses and other habitat on the bay floor, while the incoming fresh water replaces the brackish water many ecosystems in the bay require. When rain from Tropical Storm Agnes flooded the bay in 1972, the entire biological community was disrupted, and oysters and soft-shell clams were particularly hard hit. The flooding from Lee was less severe than Agnes, so the impact may not be as extreme.

Source: NASA