Short Term
Long Term
Setting a Precedent


Long Term: Wetlands
Written by Anna Simon

Currently, Louisiana’s wetlands are being lost at a staggering rate; annual net wetland loss is estimated at 75 square kilometers per year (USGS Fact Sheet: Louisiana’s Coastal Resources).  The Coast 2050 report projects that without action, southeastern Louisiana will lose 412,580 of its two million acres of wetland in the next hundred years; this estimate is pre-Katrina and may be somewhat conservative (Barrier Island Feasibility Study).

With preventative action, this loss can be reduced; however, because of the environmental and political complexities of the factors relating to the loss of wetlands, a goal of a net gain, or even no net loss of the wetlands is unfortunately not a reasonable goal.  Instead, the goals for maintaining the wetlands over the next hundred years should be to

  1. Mitigate wetland loss as much as possible by restoring and creating wetlands, as well as controlling the factors that are currently causing the wetland loss in southeastern Louisiana
  2. Put special effort into controlling wetland loss in the most crucial areas for protecting New Orleans from storm surge, i.e. the barrier islands
  3. Improve and develop technology for restoring and recreating wetland habitats

It is estimated that with preventative action using current technology, southeastern Louisiana will be able to retain an additional 300,000 acres of its wetlands over the next hundred years, reducing the area lost by approximately 30% (Barrier Island Feasibility Study).  However, this estimate is extremely difficult to make, as it depends on the development of restoration technology, the number and severity of storms that will hit southeastern Louisiana, and the ecosystem dynamics and response to large-scale restoration.

In general, the hundred year plan will consist of a long-term investment and involvement in the wetlands.  Because the wetland ecosystems are complex ecosystems and the technology for restoring them is poorly understood, a high degree of monitoring and reevaluating plans based on successes and failures of restoration processes is necessary.  It would probably be optimal for committees to reevaluate and determine the needs of certain areas at least every five to ten years. 

The key aspect of the hundred year plan for the wetlands of southeastern Louisiana is to optimize the wetlands’ future potential to deflect storm surge, and protect the New Orleans area.  In order to effectively protect against storms, the wetlands themselves should be optimally healthy and well-adjusted to the projected conditions in one hundred years, specifically increased sea level and increased amount of erosion.  The two major aspects to this plan are to maintain the barrier islands but encourage their natural landward migration, and to change the species composition of areas that were formerly brackish marshes so they are less susceptible to destruction due to an increase in salinity. 

The most important aspect of hurricane protection in southeastern Louisiana is the barrier islands.  Barrier islands are Louisiana’s first and probably most important defense against hurricanes.  Barrier islands act as “speed bumps” --- as hurricanes pass over them, they lose considerable energy (Wetlands Break Waves).  Additionally, barrier islands are the keystone to the health of Louisiana’s coastal marshes, as they absorb the incoming wave energy from the Gulf of Mexico, protecting the interior wetlands from erosion.

Although Louisiana’s barrier islands are relatively low-lying, they are probably more threatened by high-energy storms like Hurricane Katrina than a rise in sea level.  When storms pass over barrier islands, the way that they lose energy is that they take it out on the barrier islands instead of the coast.   Additionally, Louisiana’s barrier islands are eroding at an artificially high rate, due to a lack of sediment entering the bays that they surround. 

The hundred year plan for barrier islands must address both the continuous, chronic erosion, and the acute effects from severe storms.  Normally, when barrier islands erode, they erode until they reach about 400-700 feet wide, and then the waves push sand onto the other side like a rug; with sea level rise, they might be eroded from both sides (Greenhouse Effect, Sea Level Rise, and Barrier Islands).  The hundred year plan, which would take such a rise in sea level into account, would include nourishing the barrier islands’ landward side in order to maintain the area of the barrier island.  The barrier islands would migrate landward, which is desirable, as it would maintain an optimal distance from the coast for protecting the coastal marshes.

However, the level of success of barrier island restoration projects has been mixed --- while some projects have been successful, others have failed to live up to expectations.  Another possible problem is that if barrier islands are eroded and renourished too quickly, stable biological communities may not have sufficient time to become established.  Additionally, previous restoration efforts have not addressed the problems associated with the amount of sea level rise expected over the next century.  Therefore, it is difficult to determine how much barrier island area can be saved in the next hundred years.   Some Coast 2050 report reports that without action, southeastern Louisiana’s barrier islands will essentially be gone in 100 years (some Coast 2050 report).

Another wetland environment that is crucial to protect in the next hundred years are fresh, intermediate, and brackish marshes.  The brackish, intermediate, and fresh marshes represent a large amount of southeastern Louisiana’s current wetland area, and a large portion of the amount projected to be lost.  Much of this loss can be attributed to salt water intrusion.  Given current conditions, significant salt water intrusion is inevitable in many areas, and should be planned for.  A possible innovative solution for salt water intrusion is to restore marshes that have experienced salt water intrusion with plants that are better adapted to survive in the new conditions.  This could be done either by replanting with improved strains of the species that was there, possibly the descendents of the individuals that survived when the others died, or with new species better suited to saline environments.  This type of replanting is still in experimental phases, but advances in this area are crucial to protecting Louisiana’s wetlands.

For every one to four square miles of wetland, the neighboring areas get a foot less of storm surge (Wetlands Break Waves).  It is difficult to quantify exactly how much the loss of a certain area of wetland will increase the height of the storm surge, but it almost definitely will in fact increase the height or the storm surge that southeastern Louisiana will experience for a particular storm.  The Coast 2050 study predicts a hundred-year increase in storm surge of 10-20%, although this estimate may be conservative (Barrier Shoreline Feasibility Study).  Probably, the amount of area of the barrier islands that can be conserved will be the most important factor in determining southeastern Louisiana’s capacity to absorb storm surge.  The decreased protection from storm surge will limit the amount of area in the New Orleans area that will be reasonably safe to live in, and therefore the sustainable number of people who can live in New Orleans.

We have estimated the quantitative effect of our proposed diversions on the wetlands.  We examined the figures from the Army Corps of Engineers’ West Bay Sediment Diversion Project, which diverts the river about Head of Passes in order to increase the sediment available to wetlands in the Plaqumithes parish.  Based on their projected rates of accretion, a distributary of 50,000 cfs would rebuild a gross 50,000 acres of wetland in 100 years.  Proportionally, our two diversions, in the MRGO channel of the Barataria Basin, of 100,000 cfs each would each rebuild a gross 100,000 acres in 100 years.  Clearly, this estimation is quite rough; the rate of accretion is not directly proportional to the volume diversion but dependent on many other environmental factors.  However, this approximation is useful because it allows for a quantitative estimate of the result of our planned diversion.

According to our estimates, approximately half of the currently existing two million acres of wetlands will be lost in the next hundred years without corrective action.  With restoration and diversion efforts, we projected to lose 700,000 out of two million acres in the next century.  Because the project wetland loss is greatest closest to the coast and southeast of New Orleans, we assumed that the net loss was approximately evenly distributed along the coast.  Therefore, we will assume that the width of the strip of coastal wetlands will be 13/20 of its current width in 100 years.  The width of the coastal wetland area is approximately 30 miles, so a loss of 7/20 of the total would result in a projected width of 20 miles in 100 years.  It is estimated that for each three to four miles of wetland, storm surge is decreased by one foot. (Coast 2050: Toward a Sustainable Coastal Louisiana; Unnatural Disasters: Natural Solutions).  Therefore, with the projected decrease in wetland area, storm surge will increase 2.5-3 feet.

This estimation is extremely rough.  The wetland loss in Louisiana is not analogous to simply taking the outermost strip off; the loss of wetlands is much patchier, as it is dependent on many factors other than proximity to the coast.  Additionally, the outlying areas that will be lost most quickly are disproportionably important to protection against hurricanes.  Specifically, barrier islands will most likely be eroded most quickly, and they are especially important for protection against hurricanes.  However, just like the other approximation, this approximation is useful because it allows for a rough idea of how the decrease in wetland area will affect the amount of storm surge.

The estimated cost for a continued, intense, restoration of southeastern Louisiana’s wetlands is approximately $14 billion dollars (Coast 2050 Report)  Although this plan for wetland restoration is expensive, the costs are necessary.  Sustaining some measure of protection from storm surge from the wetlands is crucial for the safety of the New Orleans area.  Additionally, if New Orleans is made into a historical city, ecotourism in the wetlands is a good idea, and would probably be lucrative, like Florida’s ecotourism in the Everglades.