Restoration science has evolved in recent years away from attempting to engineer the coast to working with nature to enhance natural marsh resiliency. Restoring the natural hydrology of coastal marshes allows the coast to withstand chronic and acute disturbances such as sea level rise, hurricanes, and oil spills.
One simple solution to restoring the natural flow across marshes is the removal of manmade barriers including spoil banks from canals, agricultural impoundments, and levees. Barriers restrict the natural flooding and draining regime, alter the salinity, and restrict tidal driven sediment exchange. The coast of Louisiana contains 10,000 miles of canals, dug for both oil and gas extraction and navigation. The sediment dug for the canals was placed on either side of the canal, creating spoil banks that restricted the flow over water over the marsh surface. This lead to water sitting on surface of the marsh for too long, eventually killing the grasses that hold together the soil, which resulted in extensive marsh loss. The canals also acted to funnel salt water and storm surges much further upland than would occur naturally.
Pushing what remains of the spoil banks back into the canals which they came from is an easy, inexpensive restoration technique that begins to restore the natural wetlands of Louisiana. The National Park Service will be backfilling approximately 16.5 miles of abandoned canals located in Jean Lafitte Park. In collaboration with NPS and other organizations, CRCL will help monitor the change in short and long term environmental conditions, including water level and flow, salinity, and elevation, associated with returning the spoil banks into the marsh. By restoring the natural tidal flow and decreasing water retention, we will be preserving important coastal wetland habitat.
Photo credit: Scott Eustis.
Backfilled canal at Yankee Bay in Jean Lafitte National Park. The spoil banks on either side have been pushed into the canal and the edges are beginning to fill in.