Can a 1926 spillway hold the key to restoring Louisiana’s coast?

By John A. Lopez Ph.D., Lake Pontchartrain Basin Foundation

The Bohemia Spillway area—a 12-mile reach on the east bank of the Mississippi River approximately 45 miles downriver of New Orleans—is a focus of research by the Lake Pontchartrain Basin Foundation (LPBF).  The spillway has a fascinating history.  In the 1920s, New Orleans residents had great fear of flooding from the Mississippi River, so the state authorized removal of artificial river levees to create a relief outlet for floodwater.  In 1926, the artificial river flood protection levees near the Bohemia Plantation were removed, thus creating the Bohemia Spillway.  This flood protection project also fortuitously created a wonderful scientific experiment of reintroducing the river floodwater to the adjacent wetlands.

Land Change map comparing east Bohemia Spillway to the west bank patterns of wetlands loss. (Courtesy USGS - Couvillion and others, 2011).

We find today that the wetlands near the spillway are healthier and more resilient than elsewhere in Louisiana.  Other than some modest shoreline erosion, the wetlands seem very stable.  Other causes of land loss do not seem to be active.  Typically elsewhere, oil and gas canals create direct loss of wetlands and an indirect effect by changing the wetland hydrology.  Many areas of coastal Louisiana have lingering land loss by canals created decades earlier.  Not so in Bohemia.  There is no pattern of “indirect loss”.  Rather, many canals are filling in with sediment and marsh.  Some have been completely reclaimed back to marsh.  The response to the oil and gas canals is one of resilience rather than weakness.  This resiliency is probably due to the river’s reconnection 85 years earlier.

LPBF has been investigating the spillway since 2007.  During the great spring flood of 2011, a major effort was undertaken to research and understand the interaction of the river’s overbank flooding and effect on the wetlands.  It is hoped that some of these documented natural processes can be replicated elsewhere in coastal Louisiana to make the coast more resilient.

LPBF will be releasing a major report on the spillway in 2012, as well as releasing a video introducing the Bohemia Spillway and this research.