Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Spillways can divert sand from river to rebuilt wetlands

25.07.2012
Researchers could have a new method to rebuild wetlands of the Louisiana delta, thanks to a chance finding while monitoring severe flooding of the Mississippi River.

A team of civil engineers and geologists from the University of Illinois, in collaboration with the U.S. Army Corps of Engineers, published their findings in the journal Nature Geoscience.

In the spring and summer of 2011, high floodwaters on the Mississippi prompted the corps to open the Bonnet Carre spillway. The spillway had been built to divert water from urban New Orleans after flooding in 1927. The Illinois team saw in the spillway opening a chance to study how much sand flowed from the river into the spillway wetlands.

“Whenever we have such natural disasters, it stresses the human system quite a bit,” said Praveen Kumar, a professor of civil and environmental engineering at the U. of I. “But it also offers an opportune time to look at some scientific questions that we might otherwise not be able to explore.”

Armed with funds from the National Science Foundation, the researchers went to the spillway site to monitor the sand diverted from the river to the delta wetlands. They discovered a surprising dichotomy: a mere 10 to 15 percent of water from the top of the river sloshed into the spillway, but an estimated 36 to 41 percent of the river’s sand load deposited into the Bonnet Carre.

“That was a completely unexpected finding in this particular study,” said postdoctoral researcher Jeffrey Nittrouer.

“I think one of the real strong outcomes that came from this particular study is that we happened to be lucky about where the site was placed. Back when the structure was built, the Army Corps of Engineers just wanted to get water out of the river. But it turns out that where they decided to place the spillway was a fantastic location for getting sand out as well.”

The findings were exciting to the team, because diverting river sediment has been a goal of research work to build up wetlands. Coastal wetlands act as a natural buffer against storm surges, protecting residential areas from the turbulent weather along the gulf. Under natural conditions, flooding periodically would inundate the wetlands, allowing sediment overflow to deposit incrementally over time to replace ground lost to erosion. However, since the urbanization of New Orleans, the extensively engineered levee system has cut off the river from the wetlands.

“We’re essentially putting a straitjacket on the river itself, disconnecting the river from the surrounding environment and preventing these natural exchange processes,” Nittrouer said. “Because we build communities along these rivers, we build levee systems that corral all that water and sediment and take it straight to the Gulf of Mexico.”

What caused such a large percentage of sand to divert to the spillway in such a small amount of water? The researchers believe that the local conditions at that point in the river hold the answer. The spillway is on the inside of a bend and adjacent to a sandbar.

“That acts as a means of allowing for sustained high-concentration sandy water to be positioned very near the spillway itself, so that sediment-enriched water is now spilling into the floodway and that sediment is depositing out,” Nittrouer said.

Now, the researchers will further explore how local river conditions could favor the movement of sediment from the river into the neighboring wetland spillway. They plan to use modeling and lab studies to find optimal conditions that could shunt sediment out of the river, with the eventual goal of designing other spillways that could be opened strategically to rebuild lost wetlands without flooding residential areas.

Geology professor James Best, geology and civil and environmental engineering professor Gary Parker, graduate students Ronald Cash and Matthew Czapiga, and corps engineer Christopher Brantley were co-authors of the study.

Editor’s notes: To reach Praveen Kumar, call 217-333-4688; email kumar1@illinois.edu. To reach Jeffrey Nittrouer, email jeffnitt@illinois.edu.
The paper, “Mitigating Land Loss in Coastal Louisiana by Controlled Diversion of Mississippi River Sand,” is available online.

http://www.nature.com/ngeo/journal/vaop/ncurrent/full/ngeo1525.html

Liz Ahlberg | University of Illinois
Further information:
http://www.illinois.edu

More articles from Ecology, The Environment and Conservation:

nachricht Gran Chaco: Biodiversity at High Risk
17.01.2018 | Humboldt-Universität zu Berlin

nachricht Dead trees are alive with fungi
10.01.2018 | Helmholtz Centre for Environmental Research (UFZ)

All articles from Ecology, The Environment and Conservation >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Scientists decipher key principle behind reaction of metalloenzymes

So-called pre-distorted states accelerate photochemical reactions too

What enables electrons to be transferred swiftly, for example during photosynthesis? An interdisciplinary team of researchers has worked out the details of how...

Im Focus: The first precise measurement of a single molecule's effective charge

For the first time, scientists have precisely measured the effective electrical charge of a single molecule in solution. This fundamental insight of an SNSF Professor could also pave the way for future medical diagnostics.

Electrical charge is one of the key properties that allows molecules to interact. Life itself depends on this phenomenon: many biological processes involve...

Im Focus: Paradigm shift in Paris: Encouraging an holistic view of laser machining

At the JEC World Composite Show in Paris in March 2018, the Fraunhofer Institute for Laser Technology ILT will be focusing on the latest trends and innovations in laser machining of composites. Among other things, researchers at the booth shared with the Aachen Center for Integrative Lightweight Production (AZL) will demonstrate how lasers can be used for joining, structuring, cutting and drilling composite materials.

No other industry has attracted as much public attention to composite materials as the automotive industry, which along with the aerospace industry is a driver...

Im Focus: Room-temperature multiferroic thin films and their properties

Scientists at Tokyo Institute of Technology (Tokyo Tech) and Tohoku University have developed high-quality GFO epitaxial films and systematically investigated their ferroelectric and ferromagnetic properties. They also demonstrated the room-temperature magnetocapacitance effects of these GFO thin films.

Multiferroic materials show magnetically driven ferroelectricity. They are attracting increasing attention because of their fascinating properties such as...

Im Focus: A thermometer for the oceans

Measurement of noble gases in Antarctic ice cores

The oceans are the largest global heat reservoir. As a result of man-made global warming, the temperature in the global climate system increases; around 90% of...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

10th International Symposium: “Advanced Battery Power – Kraftwerk Batterie” Münster, 10-11 April 2018

08.01.2018 | Event News

See, understand and experience the work of the future

11.12.2017 | Event News

Innovative strategies to tackle parasitic worms

08.12.2017 | Event News

 
Latest News

Gran Chaco: Biodiversity at High Risk

17.01.2018 | Ecology, The Environment and Conservation

Only an atom thick: Physicists succeed in measuring mechanical properties of 2D monolayer materials

17.01.2018 | Physics and Astronomy

Fraunhofer HHI receives AIS Technology Innovation Award 2018 for 3D Human Body Reconstruction

17.01.2018 | Awards Funding

VideoLinks
B2B-VideoLinks
More VideoLinks >>>