Deja voodoo: is marsh management coming back to life? (part une)
Editor’s note: The much-discussed guest post on the Katrina experience was broken into serial form because of its length. When this piece started becoming too long for a single post I decided to serialize it as well.
Call me crass, but my unintended experiment with back to back posts, one controversial and one blatant good news, showed that the latter generates no feedback. I’ve never been in the news business before but I’m learning.
Although the subject of this post (marsh management) doesn’t rival the powerful emotions elicited by the life-or-death lessons of Katrina, it is still a controversial topic, as you will see.
As hurricane season 2009 rolls around, constructing, armoring or elevating levees assumes the highest priority in the minds of many residents of south Louisiana. This appears to be reviving interest in an old coastal dispute involving levees that seemed to have died but that may be re-emerging.
I’m referring to the traditional cultural practice formerly known as marsh management, a sacred cow renamed during the nineties to hydrologic restoration in order to avoid controversy. Marsh management is the idea* that freshwater marshes can be preserved and sustained indefinitely by “protecting” them from natural variations in water level and salinity.
In my humble opinion, protecting freshwater marshes from coastal stresses using marsh management is tantamount to using abstinence to protect teens from the risks of sex. I believe that the widespread practice of marsh management, like damming Bayou Lafourche, was one of the huge coastal mistakes that got us where we are now.
On levees in general, there is a philosophical chasm between levees-only advocates, those who see levees as the end-all and be-all of coastal protection, and environmental purists who argue for “natural protection,” using barrier shorelines, reefs, coastal forests and marshes. This chasm has been reopened by discussions of the Morganza-to-the-Gulf Project, which is currently high on the state’s priority list for implementation.
As a reminder, the largest delta in North America, on which we live and depend, is critically dysfunctional and on life support because of the abuse it has received since Europeans first settled here. Thus I find myself conflicted on levees. The ecologist in me prefers a natural solution but the realist in me recognizes our fundamental need for levees – to protect lives and culture – but not landscape.
Sadly, by the time coastal restoration became serious, in many places we had already painted ourselves into the corner of absolute levee dependence.
While I support levees to protect population centers I strongly oppose them in remote areas, especially levees used to “manage” marshes. I support a “Taco Belle lite” version of Morganza-to-the-Gulf, not the whole, incredibly expensive, enchilada.
I referred above to a struggle in the nineties between two coastal camps: (1) advocates of marsh management, using levees and water control structures to protect freshwater wetlands from tides and saltwater; vs (2) advocates of the re-introduction of river water and sediments and nourishing barrier shorelines. The natural (science based) approach seemed to have won the day until Hurricanes Katrina and Rita thrust Morganza-to-the-Gulf into the spotlight.
Marsh management, aka hydrologic restoration, is basically the idea of “protecting” freshwater marshes in our sinking coast by surrounding (impounding) them with a levee created by the spoil dredged from a linear (four sided) borrow pit. This technique goes back to the thirties, when some of these newly “protected” wetlands were pumped out so as to “reclaim” the rich organic soils for row crops.
Such experiments inevitably failed, resulting in permanent large rectangular ponds now visible on satellite images. The agriculture projects failed because when freshwater wetlands at sea level are impounded and drained they inevitably sink below sea level as their organic soils oxidize and shrink. This was the historical fate of the “bowl” of NOLA, later of Metairie and Kenner and currently happening on the West Bank of Jefferson Parish.
To be fair, marsh management has become considerably more sophisticated over time and so-called “modern marsh management” incorporates water control structures such as flap gates to block saltwater inflow and to allow freshwater outflow. Operation and maintenance of these complex mechanisms is problematic, however.
Even with control structures, managed marshes are always at risk of being overtopped by hurricane surges, trapping salt water long enough to poison the vegetation. I have flown over such projects after hurricanes and observed large black dead rectangles. The other huge problem with marsh management is the restriction of impounded marshes to fisheries exchange.
This summer, while we intensely scrutinize weather patterns along the African coast, Supreme Court appointee Sonia Sotomayor faces intense scrutiny by the Senate re her views on the US Constitution. Would that we had a “Coastal Constitution,” an explicit set of principles for restoring a functional delta against which to confirm the “levee logic” of the folks who make coastal policy decisions!
To be continued in part deux, e.g., how alligators, oil and gas and Morganza-to-the-Gulf have influenced marsh management.
*Strongly supported by some resource agencies, including the state Department of Wildlife and Fisheries (LDWF); the federal Natural Resources Conservation Service (NRCS); and the US Fish and Wildlife Service (USFWS).