Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

'Just Right' Plant Growth May Make River Deltas Resilient

26.08.2014

Research by Indiana University geologists suggests that an intermediate amount of vegetation -- not too little and not too much -- is most effective at stabilizing freshwater river deltas.


Elizabeth Olliver, Indiana University

This image shows freshwater marsh vegetation in Wax Lake Delta, La. Aquatic vegetation on low-elevation marshes is pictured in the foreground, while woody vegetation occupies a levee on the left. The open water in the distance is a deltaic distributary channel.

The study, "Optimum vegetation height and density for inorganic sedimentation in deltaic marshes," was published online Aug. 24 by Nature Geoscience. The findings may help guide restoration of river deltas, such as those near the mouth of the Mississippi River, which are under threat as sea levels rise.

Authors are William Nardin, a postdoctoral fellow in the Department of Geological Sciences in the IU Bloomington College of Arts and Sciences; and Douglas A. Edmonds, who holds the Robert R. Shrock Professorship in Sedimentary Geology and is an assistant professor of geological sciences.

Vegetation on marsh surfaces in river deltas can slow the flow of water and cause more sediment to be deposited, helping prevent sea-level rise from drowning sensitive marshlands. But the study finds that, if the vegetation is too tall or dense, it diverts water into the river channel, resulting in less sediment being deposited on the marsh.

“In river deltas the effect of vegetation on sedimentation seems to follow the Goldilocks principle,” Edmonds said. “You want the amount of vegetation that is just right -- not too much, but also not too little.”

The world’s river deltas are rich and productive and are home to about 10 percent of the world’s population. But they are threatened by an array of forces, including population growth, pollution, development and erosion, as well as sea-level rise associated with climate change.

Edmonds wrote in a 2012 Nature Geoscience article that river deltas can be restored, but it will take a better understanding of the processes involved in their formation and destruction. The current study suggests vegetation could play a role in designing effective river delta restoration.

In tidal saltwater marshes, research has shown that vegetation enhances sedimentation. But scientists know less about how vegetation affects sedimentation in freshwater marshes that are common in river deltas. Nardin and Edmonds used sophisticated computer modeling to study how marsh vegetation influences the transport and deposition of sediment in river deltas. They conducted 75 simulations involving varying scenarios of vegetation height and density and rates of water flow.

They found that vegetation of intermediate height and density results in the greatest deposition of sand and mud. However, if the plants are too tall or densely packed, sediment tends to remain in the river channel, bypassing marshes and being carried directly to the sea.

The researchers also analyzed remote-sensing data collected from Wax Lake Delta in Louisiana. The analysis showed the delta exhibits a hydrodynamic response to the presence of vegetation that corresponds with what the researchers found with their model.

The rate at which sediment is delivered to marshes in river deltas is strongly influenced by storms and flooding, as well as the construction of engineered diversions. The research suggests the resilience of river deltas will depend on the timing of floods and storms relative to the seasonal growth of vegetation. And of course, scientists can’t control or even predict when floods will occur.

“That unpredictability adds an interesting twist to the problem,” Edmonds said. “The time that the flood wave arrives does not always coincide with the timing of vegetation growth and decay. Those two have to line up just right for vegetation to really enhance deposition of sand and mud.”

Funding for the research came from a National Science Foundation Frontiers in Earth Systems Dynamics grant and from the Alfred P. Sloan Foundation. To speak with Edmonds or Nardin, contact Steve Hinnefeld with IU Communications, 812-856-3488 or slhinnef@iu.edu.

Steve Hinnefeld | newswise
Further information:
http://www.iu.edu

Further reports about: Geoscience Nature River construction floods marshes marshlands sedimentation storms

More articles from Earth Sciences:

nachricht Answer to restoring lost island biodiversity found in fossils
23.09.2014 | University of Florida

nachricht Snail shells show high-rise plateau is much lower than it used to be
23.09.2014 | University of Washington

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

Anzeige

Anzeige

Event News

Future questions regarding data processing

22.09.2014 | Event News

"Start-ups and spin-offs funding – Public and private policies", 14th October 2014

12.09.2014 | Event News

BALTIC 2014: Baltic Sea Geologists meet in Warnemünde

03.09.2014 | Event News

 
Latest News

New chip promising for tumor-targeting research

23.09.2014 | Medical Engineering

Answer to restoring lost island biodiversity found in fossils

23.09.2014 | Earth Sciences

Old drug may be key to new antibiotics

23.09.2014 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>