PUNCTUATED COASTAL REORGANIZATION: A LESSON LEARNED FROM HURRICANE KATRINA?

Hurricane Katrina's category 4 landfall along the Plaquemine shoreline of southeastern Louisiana created an unparalleled level of abrupt alteration and reorganization to the geomorphology, ecosystems, and sociology of the Louisiana coastal zone. Hurricane Katrina ranks as the nations' most widespread natural disaster in terms of loss of life, property destruction, and rapid displacement of hundreds of thousands of people. The potential of landfall of a catastrophic hurricane along southeastern Louisiana had been, for many years, soothsaid by a wide array of scientists, engineers, sociologists, and legislators. In response, numerous plans were developed and partially implemented that provided protection for the ecosystem and society of the region by restoring the rapidly disappearing coastal wetlands and barrier island systems. These geomorphologic elements afford protection to interior wetlands and communities by diminishing the storm surge and retarding the intrusion of marine waters, thereby reducing impacts to the wetland ecosystem and lessening the overall loss of life, property, and infrastructure during a major storm impact. The Louisiana Coastal Area (LCA) study of 2004, jointly developed and completed by state, federal, and private entities, was initially undertaken to alert federal legislators and the public to the potential hazard associated with a deteriorating coastal zone becoming increasingly susceptible to storm impacts. The LCA study specifically identified the need to preserve and restore the coastal zone and requested federal funding to cost share these efforts with the state of Louisiana. Although some federal funding was pledged as a result of the LCA report, it was too little too late; this is evident for example, in the failure of an under-funded and inadequate storm-surge protection system for New Orleans. What have we learned about the future of the coastal zone from this disaster? From a geologic perspective the coastal zone of the north-central Gulf is forever changed as a result of Katrina; barriers have been extensively breached and reduced in size and large areas of wetland have been completely removed. Some of the impacted barrier chains will reestablish and some breaches will close as sand is moved back onshore and redistributed along shore. In other instances, barriers will never be restored in the same locations. At these sites the sand comprising the barrier systems has been washed deep into the landward sounds beyond the marsh and tidal flat platform. For example portions of the Chandeleur Islands may never reform and as the result of Katrina have been transformed into subtidal sand shoals in an evolutionary tract similar to Ship Shoal. Coastal ecosystems and communities landward of the coast are now even more susceptible to hurricane impact and potential future devastation. Coastal marsh platforms that were completely eroded will never fully recover, in spite of these areas having some of the highest rates of accretion and plant growth. In a few areas, because large storms are well known to fuel the recovery of some marsh through the introduction of nutrients and sediment, some interior marsh may actually expand, become healthier, and provide an enhanced protective buffer beyond the area of direct impact. The relative balance between marsh destruction versus increased growth is yet to be determined. For several years I have discussed the necessity of Louisiana coastal restoration with three potential conceptual approaches to coastal zone protection: 1) A full restoration of the coastal zone to some previous point in time; 2) A reengineering of the coastline to protect critically important segments, communities, and vital infrastructure; 3) A managed retreat from a rapidly disintegrating coastal area that is impacted by the highest rates of relative sea-level rise in the nation. The first of these is clearly impossible as no amount of labor or monetary investment can restore the once widespread and robust coastal zone of southern Louisiana to its status of even 5 years ago. The second alternative is locally tractable because the technology exists to build storm resistant infrastructure along the coastal zone and State and Federal agencies have had success using dredged sediment to reconstruct some barrier systems and close breaches that would otherwise allow unimpeded inflow of storm surge deep into the interior wetlands and associated communities. As feared, the third option is now a likely alternative because of the impact by Katrina, rather than a plan implemented before such a devastating event. Discussions with numerous coastal zone residents indicate that many have abandoned the thought of a coastal zone life and are considering the possibilities of more inland habitation, creating a shift in the sociological shoreline and coastal demographics. Not surprisingly, numerous examples exist within historical times of similar storm-forced inland migrations and sociological reorganizations. There are suggestions that as a society we have entered into a phase of more frequent and larger tropical cyclones. Hurricane Katrina provides a clear glimpse into the future for areas of the nations' coastal areas that are susceptible to hurricane landfalls. Such impacts will most certainly induce punctuated changes in coastal zone geomorphology and processes, uniquely providing a glimpse into the role of major storms and the associated physical processes that contribute toward the construction of the geologic record. Economic necessity and shear desire will drive people to continue to inhabit coastal areas such as southern Louisiana and impacts by future storms will certainly, and unfortunately, contribute toward the loss of life and property. For these reasons punctuated coastal reorganization of geomorphology and society that is driven by future storms will occur. The lessons of Katrina however should provide for the establishment of regulations and plans that reduce future devastation by reconstructing deteriorating coastal zone buffers and limiting the re-habitation of unprotected areas that are highly susceptible to the devastation arising from large tropical cyclones and continued sea level rise.