Ditch the Ditch
Assateague Island National Seashore

Aerial view of the ditches crisscrossing a wetland
Aerial view of the ditches at Assateague Island National Seashore
NPS/ASIS

Quick Facts

GETTING READY FOR 2016:

A Call to Action
Action Item:
Revisit Leopold
Also Promotes:
Crystal Clear
Year Accomplished:
2013

Ditches in wetlands are not a new thing.  As European colonists arrived in the 17th century, they quickly learned that digging ditches in wetlands would increase their yield of certain marsh grasses.  By the 20th century, property owners were digging ditches to establish boundaries around their properties.  Later, as soldiers came home from the Civil War with malaria, local communities did everything they could to control the spread of the disease, including trying to drain wetlands.    

In the 1930s, still under the assumption that ditches would drain wetlands and therefore control mosquitoes, the Civilian Conservation Corps (CCC) started digging parallel grid ditches in wetlands up and down the Atlantic coast. When plans were made to turn Assateague into a private subdivision in the 1950s, it came as no surprise that ditches were dug on the marshes that protect the bayside of the island.  These ditches were maintained until the 1960s when scientists explained that the system didn’t work; ditching changed the hydrologic and geomorphic characteristics of wetlands and removed habitat for animals that eat mosquitoes.

Because the majority of the ditches do not fill in on their own (in fact, some widen depending on their location), Assateague Island National Seashore has been actively filling the ditches with sand since 2008. Our Resource Management team only works on this project, known as the Marsh Restoration Project, during winter months.  We have two study sites - Valentines and Tingles- where we are collecting data on the water table and surface water flow.  The preliminary data are suggesting that by filling in the ditches, the natural hydrology is being restored and water is staying on the surface of the marsh longer.  Both of these effects are desirable because certain species of native vegetation need to have their roots wet for longer periods of time.  At the same time, water lingering on the surface of the marsh longer allows it to filter into the marsh slowly so that nutrients can be taken up by plants and sediments can settle out of the water before it goes back into the bay.