Much of Gulf Coast prepping for future flooding/storm surge
Our neighbors to the east, the State of Louisiana, has had some unpleasant experiences with hurricanes as has Texas.
The state government of Louisiana, however, is moving to do something about it so future hurricanes maybe won’t be as devastating as prior ones.
In an article in “Scientific American” dated Jan. 26, 2012, author Mark Fischetti stated more than six years after Hurricane Katrina devastated the Louisiana coast, the state has proposed a plan to use wetlands to protect against future high storm surges.
“The state’s new flood plan is a sharp turn from past plans, which relied heavily on levees and seawalls to hold back rising waters. If all the plan’s provisions are carried out, it would cost $50 billion over 50 years,” he wrote.
Over the past 80 years, an almost Delaware-sized chunk of wetlands have been lost to erosion in southern Louisiana. If the wetlands plan is successful, however, the state stands to gain more land than it loses by 2042 and would gain an average of about 2.5 square miles of land per year by 2061.
The state coastal authority says it can accomplish the land gain by fortifying shredded barrier islands with sandy sediment dredged from the ocean bottom.Natural land ridges along the coast would be strengthened in a similar manner, and the two landforms would have the effect of breaking up any strong wavefronts, the plan says.
Closer inland, the plan calls for cutting diversions in Mississippi River levees, allowing more water and sediment to seep into wetlands areas when the river is running high. According to the plan, building up the land and its freshwater stores will have the effect of diluting plant-killing salt water that could wash in during a major storm.
In New Orleans, the plan suggests strengthening man-made levees and floodproofing homes and business, but wetlands improvement — at $17.9 billion — is still the single largest expenditure in the proposal.
Some fishermen have complained that increasing in-shore freshwater flows will displace shrimp, crab and other fish that prefer brackish water. They say previous experimental levee diversions have failed to rebuild land.
Studies have shown that diversions do result in improvements but those improvements are not always as significant as predicted. Either way, the effects will not be seen for a number of years.
The Coastal Protection and Restoration Authority website shows that while the future looks bleak, the state has the opportunity to take bold action to save the coast and secure south Louisiana’s future.
The CPRA’s Draft 2012 Coastal Master Plan is based on a two-year analysis involving some of the state’s best scientists as well as national and international specialists. The state used this analysis to select 145 high performing projects that could deliver measurable benefits to communities and coastal ecosystem over the coming decades. The plan shows that if these projects were fully funded, at a pricetag of $50 billion, the agency could substantially increase flood protection for communities and create a sustainable coast.
“”Louisiana is in the midst of a land loss crisis that has claimed 1,883 square miles of land since the 1930s,” the website reads. “Given the importance of so many of south Louisiana’s natural assets—its waterways, natural resources, unique culture, and wetlands—this land loss crisis is nothing short of a national emergency, one that takes a daily toll on the lives of coastal residents.
“To address this crisis the Louisiana Legislature passed Act 8 in 2006, which created the CPRA and required it to develop a coastal master plan every five years. The first master plan was approved by the legislature in 2007. The new master plan, now under public review, will be submitted to the legislature for approval this spring.”
The types of projects are as follows:
• Bank Stabilization- Onshore placement of earthen fill and vegetative plantings designed to reduce wave energies and maintain shorelines in open bays, lakes, and bayous. Bank Stabilization projects include work on navigation channels. It is the state’s policy that funding for these projects is the sole responsibility of the federal government.
• Barrier Island/Headland Restoration- Creation and restoration of dune, beach, and back barrier marsh to restore or augment Louisiana’s offshore barrier islands and headlands.
• Hydrologic Restoration- Project features that restore natural hydrologic patterns either by conveying fresh water to areas that have been cut off by man-made features or by preventing the intrusion of salt water into fresh areas through man-made channels and eroded wetlands.
• Marsh Creation- Creation of new wetlands in open water areas through sediment dredging and placement. Some projects involve pipeline conveyance of sediment.
• Sediment Diversion- Use of new channels and/or structures to divert sediment and fresh water from the Mississippi and Atchafalaya Rivers into adjacent basins.
• Channel Realignment- Use of new channels and/or structures to divert sediment and fresh water from the Mississippi and Atchafalaya Rivers into adjacent basins.
• Oyster Barrier Reefs- Establishment of bioengineered oyster reefs to improve oyster propagation and serve as breakwaters to attenuate wave energies.
• Ridge Creation- Re-establishment of historic ridges in basins through local dredging, sediment placement, and vegetative plantings to restore natural ridge functions.
• Shoreline Protection- Nearshore rock breakwaters to reduce wave energies on shorelines in open bays, lakes, sounds, and bayous. Shoreline protection projects include work on navigation channels. It is the state’s policy that funding for these projects is the sole responsibility of the federal government.
• Multiple Feature Projects- Projects that combine one or more of the above features.
• Protection Projects: Structural- Structural risk reduction projects reduce flood risk in coastal communities by acting as physical barriers against storm surge. We viewed protection through the lens of reducing communities’ expected flooding risk to either the 50 year, 100 year, or 500 year level. To this end, the 31 structural projects evaluated in the 2012 Coastal Master Plan include one or more of the following basic components:
The principal component of structural projects is the earthen levee. These structures consist of pyramidal banks of compacted earth that provide a barrier against storm surge for coastal communities and assets. Levees can either be linear in shape or ringed. Ring levees form a closed risk reduction system that encircles a protected area (referred to as a polder). Linear levees create a closed system by tying into other linear levees or by extending inland to high ground.
These are typically located at points along an earthen levee that have a high potential for erosion or insufficient space for the wide slopes of an earthen levee. Concrete walls were specified at junctions with water crossings, railroads, and major roadways (i.e., interstates and state highways).
Floodgates are needed where levees or concrete walls cross a road or railroad or where they intersect waterways. Floodgates were established for each of these crossings for the structural projects in the master plan.
Pumps are needed in enclosed risk reduction systems to allow water that enters a polder to be pumped out. Pumps were included as features of most of our protection measures.
• Protection Projects: Nonstructural- Nonstructural projects reduce storm related flood risk by modifying individual residential and commercial structures. Although many parishes have already implemented nonstructural measures to reduce flood risk within communities, we did not have a complete list of these projects, nor did we have a study of coast wide nonstructural measures to work from. To fill this gap and provide a comprehensive approach to nonstructural protection in the master plan, we developed a list of 112 possible nonstructural projects and identified where on the coast they could be located. This list was conceptual, but it allowed us to fully integrate nonstructural measures into our analysis.
Raising residential structures so that their lowest floors are higher than projected flood heights. For residential structures, this measure was considered for areas with a projected flood depth of between 3 and 18 feet.
Refitting structures to be resistant to flood damages. Residential and commercial floodproofing were considered for structures in areas with projected flood depths of 3 feet or less.
Voluntary acquisition of structures in areas where projected flood heights make elevation or floodproofing infeasible. We considered this option for residential structures that would need to be elevated higher than 18 feet. Less than 3% of the nonstructural projects recommended in the draft plan falls into this category.
Leaders in Orange County, likewise, aren’t standing idly by without preparing for future hurricanes.
Bobby Fillyaw, executive director of the Orange County Economic Development Corporation and also over the county levee project, said Orange County has completed the finishing stages of a feasibility study with the engineering firms of Carroll and Blackman, Leap Engineering and Costello Engineering. Engineers have been working on the study since the summer of 2009.
FEMA has produced new flood maps and surge maps for the area that will give leaders a better understanding.
The second stage of the project is to secure additional funding for the project to get things rolling. There was no funding prior to the Fall of 2010 -2011, Fillyaw said.
Plans are to use a gate system or Interstate 10 as a barrier on the west side of the county. A levee would also protect the east side of Jefferson County.
“This could take years to complete, even if the construction started tomorrow. You have to deal with engineering strategies, environmental issues, mitigation issues and permitting. It will take several years to do this,” Fillyaw said. “We need to find ways to fund this It could cost a lot of money. We may not be able to do it alone for Orange County.”