 It created a long and relatively shallow lake along the upper stretch of the Conejohela Valley known as Lake Clarke.The creation of the lake shrank the upper Conejohela Flats in size.The mixed marshy terrain of the Conejohela Valley contained rapids and small waterfalls, wetlands, and thick woods along both sides of the river within a ten-year floodplain which saw annual inundations all the way down into Maryland at the headwaters of Chesapeake Bay, and experienced catastrophic floods regularly (the meaning of a ten-year floodplain).