The NASA satellite image shown below appeared in an August 2012 U.S. Geological Survey report documenting the loss of sediment trapping capacity in the Conowingo Dam reservoir. The image has since been used by the Coalition as a visual reference to illustrate the downstream extent of sediment transport during major storm events. Maryland county jurisdictional boundaries have been added for contextual reference.
The photograph of the approximately 100-mile sediment plume extending from the Conowingo Dam following Tropical Storm Lee in September 2011 illustrates the scale of sediment transport associated with extreme storm events.
Estimated quantities of sediment and nutrients transported into the Chesapeake Bay during this single event are summarized below:
*According to the U.S. Geological Survey
- 42,000 tons nitrogen
- 10,600 tons phosphorus
- 19 million tons sediment (of which 4 million tons was scoured from the reservoir)
*According to the UMCES- Horn Point (Cambridge, MD) Survey
- 115,910 tons nitrogen
- 14,070 tons phosphorus
For comparison, below are the yearly pollutant loading averages from 1978-2011
- 71,000 tons nitrogen
- 3,300 tons phosphorus
- 2.5 million tons sediment
What will the next significant watershed storm event do to the Bay and to the restoration efforts below the Conowingo Dam?