Chris McLindon, Causes of Accelerated Wetlands Loss in the Late 20th Century – Southeast Louisiana (2016)
Kolker et al. (2011) found a tight coupling between patterns of land loss measured in the Barataria Basin by Couvillion et al. (2011) and their interpretation of subsidence from the historical record of the Grand Isle tidal gauge.
The relationship between subsidence and land loss in the temporal domain determined by Kolker et al. (2011) can be extended to the spatial domain using the Land Area Change Map produced by Couvillion et al. (2011). Extrapolating from the tightly bound relationship between temporal patterns of land loss and the measurement of subsidence in the Barataria Basin across the SE Louisiana coastal plain provides a first order approximation of a subsidence map. This map is integrated with a first order approximation of the traces of active faults across the surface of the coastal plain to yield a pattern of hot spots of subsidence caused by the vertical movement of faults. This pattern of hot spot subsidence (and land loss) is integrated with a map of the distributary channels of the lower Mississippi River system that were likely to have been active between the late 18th and early 20th centuries to suggest that sedimentary loading during the period of elevated suspended load of the river system (Tweel and Turner, 2012) may have triggered a period of fault movement that is responsible for the mid to late 20th century period of accelerated land loss on the coastal plain.
Oil and gas industry seismic data has been used by academic researchers to map the surface expression of faults across the south Louisiana coastal plain over the past two decades. The first academic study to use an industry 3-D seismic survey for this purpose resulted in the 2014 publication ”Influence of growth faults on coastal fluvial systems: Examples from the late Miocene to Recent Mississippi River Delta” by Armstrong et al. This study mapped 28 faults in a 1375 km2 3-D survey in Breton Sound and Barataria Bay and found that ”Most of the seismically imaged faults appear to extend up to the modern land surface and some affect the modern delta morphology.” This study did not make note of the fact one of the active surface fault traces mapped with the 3-D survey traversed the location of Magnolia site for the proposed Lower Barataria Diversion. The New Orleans Geological Society is actively promoting the use of oil and gas industry 3-D seismic data, advanced imaging technologies, and general geological knowledge base in academic research supporting the coastal restoration effort. The proper planning and design of restoration projects relative to the underlying geological structure of the wetlands would be the most effective way to insure long term sustainability of the projects.
Coastal change is unlikely to require new law but properly dealing with its effects and planning our response to them will require more than just a good understanding of present law. Statutes rest on fundamental – but often unstated – societal assumptions favoring some outcomes and denying others. For example, Western societies presume land should remain in commerce and always be productive.
Virtually all of the major cases and controversies concerning water and/or coastal issues arising around the nation in recent years – property damage and land loss during hurricanes due to exploration and production (E & P) canals, increased expenses to levee boards from a subset of those same E & P canals, diversions affecting oyster beds, beach front lot owners objecting to beach restoration projects, Anthropogenic climate change causing increasing hurricane damage – were all resolved by applying existing law. Many of those laws are not just based upon Roman laws going back over 2,000 years; some are almost word-for-word copies of them.
Unfortunately, much of the general public either does not understand the basic principles of land use and tort or perhaps simply wishes for different outcomes despite existing (and well-settled) laws. Worse, there does not seem to be sufficient appreciation of the underlying geological factors driving some of the changes in and along our coasts, marshes, and swamps.
Law as an institution has never attempted to “control nature” per se but it most assuredly attempts to specify and control who gains and who loses - and why – when a river changes course, when new land forms at the beach, and when a dispute breaks out as to “what is a beach?” and “who owns it?”
A general overview of the major cases and an explanation of why they turned out as they did will better enable coastal planners to find – and stay within – more realistic limits of what can and cannot be accomplished within the framework of our existing laws. Moreover, if American society does determine a new direction in coastal programs is needed, a fuller understanding of current law will likely allow better choices to be consciously made. However, since law can only help illuminate the choices and assign the risks to various parties, ultimately geology – not law – is the key to future decisions about our coastlines.