Glaciers, storms, tides and winds are constantly creating and destroying islands and shorelines throughout the Chesapeake Bay region. According to Maryland settler and Jesuit missionary Father Andrew White, St. Clement's Island was 400 acres in 1634. Today, the island, measured with Global Positioning System (GPS), has been reduced by erosion to 62 acres.
During the 1920s, the Federal Government used layers of large stones, called riprap, to control erosion near the Blackistone Island Lighthouse. Fifty years later, through the efforts of the St. Mary's Historical Society and the State of Maryland, riprap now surrounds the entire island. The Maryland Park Service continues efforts to slow the effects of erosion by allowing vegetation to grow and by limiting recreational use of the island.
Hurricane Isabel's Devastation
During Hurricane Isabel in 2003, the Potomac waters forced a wall of riprap to collapse and washed away a portion of the island's bank. The fury of scores of hurricanes has shaped the Chesapeake Bay islands and beaches for more than 10,000 years.
[map image] A survey map, last revised by the military in 1920, illustrates how the island had changed shape and decrease in size since the 1883 survey.
[1920s photo] A 1920s photo, taken from the Blackistone Island Lighthouse tower, shows a riprap being used to protect the lighthouse grounds.
[photo] Riprap is more than rocks
A filter fabric is placed behind the riprap, making the erosion control more effective. The fabric allows the water to flow off the island and traps the soil normally lost in the run off.