FTB36 - Barrier Island Shifts, Documented

Between 1984 and 2007, Karen Westphal* used time-lapse aerial photography to document shifting barrier islands along the Louisiana Coast while longshore transport, breaking waves, built structures, and other factors impact the movement of sand and sediment. Check out the links:

• interactive photo-map of multiple Louisiana delta complexes and chenier (coastal ridge) plains, 1984-2007
• photo pairings of Louisiana shoreline comparing 2001 + 2005 (pre- and post-Hurricanes Katrina + Rita)
• photo pairings of East + West Louisiana shorelines 2005-2007 (post-Hurricanes K+R)

I find the following images to be very helpful in understanding the processes that Karen has documented.

Barrier island accretion through drumstick model.  The opposite can also happen, as an island is split by wave washover.

Grand Isle, Lousiana.  Photo taken from edge of beach.  Note how currents have dropped sand loads between beach and rock wall.  Birds often hunt here.

From Andrew Barron of Barataria Terrebonne National Estuary Program (BTNEP)

relatively new delta lobes of the Mississippi River, now constrained to the Balize delta course

older geologic features, well below the surface

Southeastern Louisiana is disappearing.  It's well-known, and it's a complicated equation.  Levees and human-made hydrologic barriers prevent Mississippi River sediment from building land atop fault lines while industry drains subterranean oil reserves and salt domes.  Trade channels have altered salinity throughout the Pontchartrain Basin while Gulf wetlands are devastated by salinity intrusion through exploratory oil canals.  The region's urban areas are subsiding after pumping all water away from development, drying out soils that rely upon water for structural stability, and replacing swampland with impervious surfaces.  That's not all, but it's a start.  Long story short: in the history of development along the lower Mississippi, natural systems have not been given due attention.  Engineering did not beat out nature, and we are now short of breath (and money) trying to catch up.  Natural systems shift and adapt, often more slowly and powerfully than human-built systems.  The barrier islands of Louisiana are a great example of this.

*Karen is a scientist working for National Audubon Society's Louisiana Coastal Initiative and is involved coordinating the Louisiana Master Naturalist Program.  I'm stoked that she shared this with me, I hope you enjoy it.