Wednesday, September 10, 2008

When Mountains Move

The recent series of tropical storms and hurricanes traversing the Caribbean have caused considerable loss of life and property. Pictures of Haiti in the news media show extensive flooding, destroyed buildings, and homeless people wading through ankle-high and deeper water. Some of those pictures also show mud-filled streets.

One of the causes of the flooding and sedimentation is the loss of vegetation on the hillsides. Haitian colliers have cut down stands of trees to make charcoal, an important cooking fuel, and the more level portions of those once forested tracts are now in cultivation. Without that dense vegetation, the water runs unimpeded down the slopes and into cities and villages. With light and moderate rains, the amount of sedimentation is probably negligible, perhaps even unnoticed by residents; but heavy rainfall causes catastrophic destruction.

In some ways, recent events in Haiti illuminate Port Tobacco's past. Like the Haitians, Americans extensively cleared the Port Tobacco valley. The resulting sedimentation...gradual and catastrophic...filled the river and covered portions of the floodplain. In previous posts I've shown that a foot or more of gravelly sediment had been deposited within the town. Throughout the 20th century, much of the land in the area has reverted to forest, greatly reducing the movement of sediments. But there is still sedimentation on a smaller scale and it continues to choke the remaining open waters of the Port Tobacco River.

Our new traveling exhibit deals with these issues and the role of archaeology in studying the changing landscape over centuries and millennia. It debuts at the Charles County Fair this week...see you there.


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