Moving Land: Erosion and Sediments

Land loss and land gain are terms we throw around a lot at CWPPRA but what do they mean? Where does the old land go and where does the new land come from? To answer that, we need to understand that “land” is made of inorganic particles that we call sediment and various types of organic matter. Sand, clay, gravel, boulders, and silt are all types of sediment, and grain size is how we classify them. [1] For example, a boulder is larger than gravel, which is larger than a grain of sand, which is larger than a silt particle, etc. Sediment size influences how each grain experiences force and inertia, which leads to different rates of land loss and gain between sediments. Imagine holding a handful of sand in one hand and a handful of gravel in the other. Now imagine you blow as hard as you can on each one. More gravel would stay in your hand than sand. The same is true of sediment in water- smaller grains of sand can be picked up more easily by the forces acting on them than the gravel can.

Erosion detaches sediment from an original source, such as a cliff face or the middle of a valley. Over long periods of time, eroded particles get smaller and smaller, eventually degrading to sand or silt, depending on the mineral base. Once they get into a river or stream, their movement is connected to water flow. When water flows faster or stronger, it “suspends” and carries more sediment, while sediments in slower currents tend to settle out and “deposit” on the bottom of the lake, bayou, or swamp. Approximately 40% of the USA drains through the Mississippi River, and any suspended sediment in those waterways travels through Louisiana on its way to the Gulf of Mexico. [2]

Sediments move downstream differently depending on their size class.

Wetlands are defined by sediment type and other characteristics including salinity. In Louisiana, we have fresh water wetlands like swamps and bottomland hardwood forests, but also saline wetlands like salt and brackish marsh. Each of these wetlands types contains fine sediment particles, and they are all relatively new in the scope of geologic time. Because they are young, there are not many hard-packed substrates in Louisiana wetlands, but instead deeper layers of sediment that are compacting and subsiding. [3] Sediment replenishment is important to all the wetlands in Louisiana because new sediment is needed on top of compacting sediment to maintain elevations that support plant life and productive ecosystems. Unfortunately, sediments that should be replenishing the wetlands of Louisiana are not doing so. Instead, they are being transported out into the Gulf of Mexico or are trapped farther upstream behind dams. More information about this topic can be found in our post “The Mississippi River Deltaic Cycle”. Controlling the flow of the Mississippi river keeps sediments suspended for longer because water does not disperse or slow down as it naturally wants to. Without new sediment, marsh platforms lose structural integrity and they erode, leaving open water where marsh once was.

To answer the original question; for CWPPRA land loss is the process of sediment and marsh sinking or eroding into open water along Louisiana’s coastline and reducing the land available. Land gain describes the process of sediment depositing to form new platforms and it is much less common along our coast, but CWPPRA and their Partners in Restoration are working to restore the integrity of coastal wetlands by moving and capturing sediment, planting stabilizing species on terraces, and creating marsh in critical areas. Combating land loss is a multi-disciplinary effort, and we have a long fight ahead.

 

Featured image: http://amazonwaters.org/waters/river-types/whitewater-rivers/

Embedded image: http://blog.sustainability.colostate.edu/?q=schook

[1] https://www.tulane.edu/~sanelson/eens1110/sedrx.htm

[2] https://www.nps.gov/miss/riverfacts.htm

[3] https://www.sciencedirect.com/science/article/pii/S027277140600312X

The Watershed Flood Center

On May 4, 2018, the University of Louisiana introduced an important new venture: The Watershed Flood Center. [1] In response to massive flooding in August of 2016 in Southern Louisiana, experts will come together to develop a better understanding of flooding in the area. Torrential downpours hit the state consistently on August 12 and 13 of 2016, amounting to more than 31 inches in Watson, LA, and more than 20 inches in Lafayette, the new home base for the Center. Atmospheric conditions caused a series of storms to form and stay over southern Louisiana for those two days, dropping and estimated 2 inches of water per hour. [2] Across the state, an estimated 7.1 trillion gallons of rain came down on August 12th and 13th, more than three times the volume Louisiana received during Hurricane Katrina in 2005.  The flooding caused an estimated $10-15 billion dollars in damages across the affected parishes, including almost 150,000 homes and businesses. [3] This catastrophe was called a 1-in-1000-year flood because meteorologists attributed a .1% chance to something of this scale happening in any given year based on past events. The Watershed Flood Center seeks to study how much that chance may be increasing with projected changes in atmospheric and climatic conditions.

Basins that will be researched at the new center | Source [1]

Wetlands are adapted to flooded conditions, so they are great for mitigating floodwaters. Mitigation allows water to be stored and released when needed, so they act like a sponge. Unfortunately, the sheer volume of water that came and stayed was too much to redirect into neighboring wetlands. Wetlands used to be more prominent but as towns and cities expand into wetlands, mitigation potential of those wetlands diminishes. Thanks to development and decreased wetland area, much of the flooded area was inundated and impassable for over a week even after the rain had stopped.

The new center at The University of Louisiana at Lafayette is far from the only research venture the university funds. ULL has many research centers and partners, including LUMCON, the Ecology Center, and the Informatics Research Institute, to name a few. These centers study many branches of science, including infectious diseases, immersive technologies, ion beams, and soon the list will include the flood-condition hydrology of Louisiana. The Watershed Flood Center is currently in development and, once completed, will study flood events with real-time monitoring to develop better forecasts to protect public interests. [4]

 

[1] https://thecurrentla.com/2018/a-new-flood-research-center-launched-to-put-fractured-regional-efforts-on-the-same-page/

[2] https://en.wikipedia.org/wiki/2016_Louisiana_floods

[3] https://weather.com/forecast/regional/news/rain-flood-threat-south-mississippi-ohio-valley

[4] https://floodcenter.louisiana.edu/research/projects

Featured image from http://www.theadvocate.com/louisiana_flood_2016/article_dbfba072-7148-11e6-a7b4-0f0b3863c31e.html

Marsh Island Hydrologic Restoration (TV-14)

banner_tv-14.fwReasons to Restore:

  • Natural erosion
  • Subsidence
  • Construction of navigation canals along the northeast shoreline of a Marsh Island.
  • Deterioration of the north rim of Lake Sand and the interior marshes.

Restoration Strategy:

  • Stabilizes the northeastern shoreline of Marsh Island.
  • Stabilizing the northern shoreline of Lake Sand.
  • Help restore the historic hydrology.
  • Construction of 7 closures for oil and gas canals at the northeast end of Marsh Island.
  • Protect the northeast shoreline with rock including the isolation of Lake Sand from Vermilion Bay.

TV14_map

[2]

Location:

This project is located in Iberia Parish, Louisiana, on the eastern portion of the Russell Sage Foundation Marsh Island State Wildlife Refuge and surrounding Lake Sand.

final_map_Tv14

Project Effectiveness [1]:

  • Effective at reducing water level variability within the northern portion of the project area
  • Water level variability did not increase in the project area as is did in R1 post-construction
  • Reducing erosion rates at the northeast shoreline was partially met
  • Reduced erosion in areas of applied rock dikes versus unprotected areas.
  • The steel sheet pile, rock rip-rap wingwall, and stone bank paving installed at each end of closure No. 5 proved to be successful in preventing erosion during a storm event.

Previous Progress [2]:

  • The monitoring plan was finalized in January 2000 following with further data collection.
  • Pre-construction and post-construction aerial photography were in the year 2000, and 2009 with future imagery analyses upcoming.
  • Water level, submerged aquatic vegetation and shoreline position and movement data were also collected to evaluate project effectiveness.

Progress to Date [1]:

  • Construction was completed in December 2001.
  • This is one of the three projects nearing the end of their 20 year lives.
  • The Task Force will vote on the Technical Committee’s recommendation on the path forward for the following projects [1]:

3 projects

This project is on Priority Project List (PPL) 6.

Project Sponsors Include:

                     US_AOE_Logo

 

  CPRA_logo_sponsor                

Source:

[1] Mouledous, M. and Broussard, D. 2014. 2014 Operations, Maintenance, and Monitoring Report for Marsh Island Hydrologic Restoration. Coastal Protection and Restoration Authority (CPRA). Available:https://lacoast.gov/ocmc/MailContent.aspx?ID=10092 [May 22,2018].

[2] Marsh Island Hydrologic Restoration (TV-14) Land-Water Classification. 2009. Coastal Wetlands Planning, Protection, and Restoration Act (CWPPRA). Available: https://www.lacoast.gov/products/sab_net_pub_products/map/original/2011-02-0009.pdf [May 22, 2018].

Salt Water Intrusion

When it comes to Louisiana, there is no one reason for coastal land loss. Causes are both natural and man-made, but when those forces combine, they are detrimental to Louisiana’s coast. One example contributing to these synergistic forces is known as salt water intrusion.

Facts about Salt Water Intrusion: [4]

  • May occur in freshwater systems like aquifers or coastal marshes.
  • Is the movement of saltwater into interior areas or underground sources such as aquifers of freshwater marsh.
  • Most common in coastal regions, where freshwater is displaced by the inland movement of saltwater from the ocean.
  • Can also occur inland, far away from an ocean, as freshwater is pumped out from underground reservoirs and the salt-laden water from surrounding salty layers of the earth flow in.
  • Most common cause of saltwater intrusion is the pumping of freshwater from wells near coasts.
  • Climate change can increase saltwater encroachment along coastal regions as sea level rises.
  • Increased salinity of coastal freshwater can threaten the plant life and wildlife of coastal areas, destroy habitats such as marshes, and force the abandonment of drinking-water supplies.

swi_22

Coastal Louisiana is currently experiencing higher than expected salinity in traditionally freshwater marshes, waterways, and reservoirs [1]. It is possible for wildlife to adapt to locally saline conditions, but that is a process that requires time. A study by two professors at the University of Louisiana at Lafayette concluded:

  • Resident marsh fishes have genetic adaptations for localized salinity conditions [1].
  • Continued adaptation will be most successful if salinity increases gradually [1].
  • The existence of adaptation to salinity tolerance will be most important in aiding survival during surges of high salinity, such as those associated with hurricanes [1].

At the same time that sea level is rising, man-made actions are intensifying salt water intrusion through [4]:

  • Canal dredging, including oil and gas access canals
  • Channelization or straightening of natural waterways
  • Construction of levees for flood control
  • General development activities in the coastal zone

CWPPRA hydrologic restoration projects help reduce the inland march of salt water. Culverts and pumps restore the flow of freshwater into marshes, while locks and weirs create “one-way” channels out of the marsh that salt water can’t access.

Help Prevent Salt Water Intrusion
Coastal Zone Management Solutions for Salt Water Intrusion
[5] Educational Video (3minutes and 42 sec):   Testing the limits of salt water intrusion 
[6] Educational Video (13minutes 50 sec): A Video Presentation of Saltwater Intrusion from a student of the University of Idaho.
[7] Educational Video (1minute 49sec): Saltwater intrusion threatens rice acres
[8] Educational Video: 12min 05sec): Rosemary Knight, “Sentinel Geophysics: Imaging Saltwater Intrusion from Monterey to Santa Cruz”.

Source:

[1] Leberg, P. and Klerks, P. 2004. Final Report: Saltwater Intrusion On The Gulf Coast: An Assessment Of The Interactions Of Salinity Stress, Genetic Diversity And Population Characteristics Of Fish Inhabiting Coastal Marshes. University of Louisiana at Lafayette (ULL). Available: https://cfpub.epa.gov/ncer_abstracts/index.cfm/fuseaction/display.highlight/abstract/5385 [May 22, 2018].

[2] Spatafora, James. 2008. Saltwater Intrusion of Coastal Aquifers in the U.S. Available: http://kanat.jsc.vsc.edu/student/spatafora/default.htm#homepage  [May 22, 2018].

[3] Encyclopedia.com. 2018. Available: https://www.encyclopedia.com/environment/energy-government-and-defense-magazines/saltwater-intrusion [May 22, 2018].

[4] Southern Regional Water Program. 2018. Louisiana Environmental Restoration. Available: http://srwqis.tamu.edu/louisiana/program-information/louisiana-target-themes/watershed-restoration/ [May 22, 2018].

[5] Fowler, Kristen. “Saltwater Intrusion – EnvS 546 Univ of Idaho”. ” 23 April 2016. Online video clip. YouTube. Accessed on 24 May 2018. <http://www.youtube.com/watch?v=puSkP3uym5k>

[6] PBS Newshour. “Testing the limits of saltwater intrusion”. 17 September 2015. Online video clip. Youtube. Accessed on 24 May 2018. https://www.youtube.com/watch?v=75CoHNQVbY8

[7] LSU AgCenter Video Archive. “Saltwater intrusion threatens rice acres”. 8 Jan 2016. Online video clip. Youtube. Accessed on 24 May 2018. https://www.youtube.com/watch?v=Z4TGPtq4bD0

[8] Stanford Alumni. Rosemary Knight, “Sentinel Geophysics: Imaging Saltwater Intrusion from Monterey to Santa Cruz”. 2 April 2014. Online video clip. Youtube. Accessed on 24 May 2018. https://www.youtube.com/watch?v=k4XcBx7OT3Y

 

 

 

Louisiana Coastal Land Loss: A Local Example, A Global Concern

Effects of global climate change, such as sea-level rise, continue to affect Louisiana’s coastal populations and economy. Some may not know that Louisiana’s coast is also known as “America’s Wetland”. It derives its name from the vast expanse of wetlands along the coast (Louisiana contains 40% of all tidal marshes in the continental United States [1]).

Benefits provided by the Louisiana Coastland:

  • Louisiana produces 30% of all coastal fisheries in the continental U.S. [1]
  • Louisiana serves 90% of the nation’s offshore energy, and 30% of the U.S. oil and gas supply [5]
  • Louisiana wetlands provides vital hurricane protection to the 2 million citizens living in the area [1]
  • Louisiana’s boating ports provide access for 31 states [5]
  • Louisiana is home to one of America’s most remarkable cultures [1]
  • Louisiana is an area of world ecological significance for wildlife [1]

Coastal land loss has affected the people and environment of Louisiana for more than a century now. According to the New York Times, Isle de Jean Charles climate refugees are an example of the new and massive problem the world may be facing in the coming decades [2]. The island has lost 98 percent of its land area since 1955 as sea levels rise and land is lost to the Gulf of Mexico. Most Isle de Jean Charles residents are Native American and tribal members of the Biloxi-Chitimacha-Choctaw Indians as well as the United Houma Nation [3].

tribes_losing

In 2016, “the community of Isle de Jean Charles became the first U.S. group of “climate refugees” to receive federal assistance for a large-scale retreat from the effects of climate change” [3]. The terms “migration with dignity” or “planned relocation” are preferred over “climate refugees” [4]. Other American groups considered “climate refugees” are the Quinault Indian Nation of the Pacific Northwest and the Inupiat of Kivalina, Alaska [4].

Dr. Julia Meaton from the University of Huddersfield’s Centre for Sustainable and Resilient Communities, mentioned, “Most people don’t engage with climate change because they perceive it as a distant phenomenon. They think there’s nothing they can do and technology or governments will solve the problem”; she also notes, “we worry about our children and our grandchildren but we don’t worry about the future for our children’s grandchildren” [7].

delta compare 2.png

National Oceanic and Atmospheric Administration scientists  (NOAA) say that by the year 2100, the Gulf of Mexico could rise as much as 4.3 feet across the Louisiana landscape [5]. Dr. Julia Meaton from the University of Huddersfield says, “an estimated 250 million people will be climate change refugees by the year 2050″ [7]. She also mentioned that to combat to global climate change “we need to completely change our business models, consume less, increase energy efficiency,  and make fewer demands on the world’s natural resources [7].

Economic losses that Louisiana experiences may expand across the nation. Louisiana coastal land loss is not just a state problem, but also a national concern and a global example of future issues resulting from climate change. A diverse group of partners, including the Coastal Wetlands Planning, Protection, and Restoration Act, are working to slow land loss and rebuild wetlands across Louisiana’s coast through large-scale restoration projects and public outreach.

la basins 3

How YOU CAN Help:

  1. Participate in a wetland restoration plan. Contribute your professional expertise or elbow grease through wetland clean-ups, replanting, and other activities [1]. 
  2. Become involved in local government actions that affect wetlands. You can request to receive the agenda of project planning meetings and copies of documents covering any restoration issues [1].
  3. Speak out for protection for Louisiana’s coast and coastal wetlands, marshes, cheniers and barrier islands to your elected officials. Let them know the coast has a voting constituency [1].
  4. Observe development practices in Louisiana’s coastal zone to determine if erosion and pollution control is effective and report violations to city and county officials [1].
  5. Encourage neighbors, developers and state and local governments to protect wetlands in your watershed resolutions, ordinances, and laws [1].
  6. Learn more about wetland restoration activities in your area; seek and support opportunities to restore degraded wetlands. You can even obtain technical and financial assistance if you wish to restore wetlands on your property [1].

More ways to Help!

 

Click a Link Below for further reading!

Isle de Jean Charles Official Website

Reclaiming Native Ground

Loyola Center for Environmental Communication

LSU: Climate Change: What will it mean for Louisiana’s Coastal Fisheries?

PRI: Louisiana’s Coastline is disappearing at the rate of a football field an hour

Scientific American: Losing Ground: Southeast Louisiana is Disappearing, Quickly

Climate Refugees Film

Louisiana Fights the Sea, and loses

 

Sources:

[1] America’s Wetland Foundation: Campaign to Save Coastal Louisiana. 14 May 2018. http://www.americaswetlandresources.com/index.html

[2] Davenport, Coral and Robertson, Campell. “Resettling the first American Climate Refugees”. 14 May 2018, https://www.nytimes.com/2016/05/03/us/resettling-the-first-american-climate-refugees.html

[3] Johnson, Chevel. “As Louisiana Shrings State Paying to Move Residents”. 14 May 2018, http://www.foxnews.com/us/2018/03/21/as-louisiana-island-shrinks-state-paying-to-move-residents.html

[4] Lenferna, Alex. “Don’t Celebrate the U.S. for Protecting Climate “Refugees”. 14 May 2018, https://www.huffingtonpost.com/entry/opinion-lenferna-climate-refugees_us_5aa92f40e4b001c8bf15db8f

[5] Marshall, Bob. “Losing Ground:Southeast Lousiana Is Disapperaing Quickly”. 14 May 2018, https://www.scientificamerican.com/article/losing-ground-southeast-louisiana-is-disappearing-quickly/#

[6] Reckdahl, Katy. “Losing Louisiana”. 14 May 2018, http://stories.weather.com/story/5931

[7] Stelfox, Hilary. “250 million people will be climate change refugees by 2050, predicts Huddersfield University academic”. https://www.examiner.co.uk/news/west-yorkshire-news/250-million-people-climate-change-10664041

[8] Featured Image: https://www.nasa.gov/press-release/nasa-releases-detailed-global-climate-change-projections

 

Rockefeller Refuge Gulf Shoreline Stabilization (ME-18)

wordpress fact sheet banner ME-18-01

The project is designed to address Rockefeller Wildlife
Refuge gulf shoreline retreat that averages approximately
46 feet/year with a subsequent direct loss of emergent saline
marsh.

The project will construct shoreline protection along the Gulf
of Mexico. A rock breakwater with lightweight aggregate
core will be tied into the west bank of Joseph Harbor
and constructed westward along the gulf shoreline for
approximately 3 miles. The structure is designed to reduce
shoreline retreat along this stretch of gulf shoreline, as well
as promote shallowing, settling out, and natural vegetative
colonization of the overwash material landward of the
breakwater. Gaps will be constructed between breakwater
segments to facilitate material and organism linkages.

ME-18 Map

The project is located along the Rockefeller Wildlife Refuge
Gulf of Mexico shoreline from Joseph’s Harbor canal,
westward 3 miles in Cameron Parish, Louisiana.

Engineering and design are complete. Construction on this
project has begun.

This project is listed on Priority Project List 10.

The Sponsors for this project include:

The Mississippi River Deltaic Cycle

Water flows downhill naturally and, over time, will make a river change from one path to another. As sediment moved and elevations changed over the last 7 millennia, the Mississippi River has emptied into several historic delta complexes: Maringouin, Teche, St. Bernard, Lafourche, Plaquemines-Balize, and Atchafalaya. Each of the deltas built up part of Louisiana’s coast to what we see today, but now that natural process has been interrupted [1]. After the great Mississippi flood of 1927 that caused $1 billion worth of damages (almost $1 trillion in today’s dollars), the US Army Corps of Engineers built the world’s longest levee system under the Flood Control Act of 1928. The Levee system was constructed to reduce flood damages and allow for more control of the Mississippi [2].

Image 1: Historic Deltas of the Mississippi River

An unforeseen and unfavorable side effect to taming the river was that all the water is kept moving too quickly to deposit sediment, and now sediment is lost to the Gulf of Mexico rather than deposited into our coastal wetlands [3]. Our Louisiana coastline is dependent on new sediment to nourish wetland ecosystems. Without sediment delivery, there is no material for natural land gain or replenishment, which will continue to contribute to our retreating coastline. The solution is not as simple as removing the levee system, however, since so much of Louisiana is populated now, and removing the levees containing the Mississippi would displace millions of residents from their homes. Instead, CWPPRA and our partners in restoration use man-made systems to create marsh, nourish wetlands, and maintain hydrologic connectivity so that we can protect and restore Louisiana’s coast.

 

 

[1] https://en.wikipedia.org/wiki/Mississippi_River_Delta

[2] https://en.wikipedia.org/wiki/Great_Mississippi_Flood_of_1927

[3] http://mississippiriverdelta.org/our-coastal-crisis/wasted-sediment/

Image 1 from https://www.nationalgeographic.org/photo/miss-delta-formation/

Featured image from https://phys.org/news/2015-04-future-mississippi-delta.html