Download Coastal Ocean Institute 2012 Funded Project Final Project Report

Coastal Ocean Institute
2012 Funded Project
Final Project Report
Project Title:
Using Sedimentary Deposits from Oxbow Lakes for Reconstructing Floods and
Anthropogenic Impacts on the Mississippi Delta
What were the primary questions you were trying to address with this research? (Or, if more
appropriate, was there a hypothesis or theory that you were trying to prove or disprove?)
Floods on large rivers are among the costliest hazards for human habitation and economy but
are essential for preserving floodplain, deltaic and other wetland ecosystems. Historical
hydrographic measurements are limited to last 200 years, which is not a long enough period to
assess the impact of climate changes on the flood regime. We hypothesized that the history of
floods can be reconstructed from sedimentary records in oxbow lakes (former river meanders cut
off from the main course).
What have you discovered or learned that you didn't know before you started this work?
By using sediment cores we learned that indeed a history of floods can be retrieved by time
overlapping records in multiple oxbow lakes.
What is the significance of your findings for others working in this field of inquiry and for the
broader scientific community?
Long term flood regimes are difficult to reconstruct. Traditional attempts have used sediments
from the upper drainage basins but they are not representative for floods at the river mouth.
Oxbow lakes present the first true opportunity to overcome this knowledge gap.
What is the significance of this research for society?
Mississippi delta is heavily affected by climate change, sea level rise, and sediment deficits.
Restoration depends on sediment delivery during floods. Changes in hydroclimate are becoming
major problems in the context of the ongoing climate change. A better understanding of the flood
regime on the Mississippi would provide knowledge for delta restoration as well as for the
protection and adaptation of people and the economy.
What were the most unusual or unexpected results and opportunities in this investigation?
Sediments from 2 oxbow lakes show a very similar history of deposition, which means that floods
affect large swaths of the floodplain and cores from lakes have a high potential to be statistically
representative.
What were the greatest challenges and difficulties?
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Obtaining good ages for sediment deposition emerged as a serious challenge. However,
employing other dating techniques besides radiocarbon that has been used so far is expected to
deal efficiently with this problem.
When and where was this investigation conducted? (For instance, did you conduct new field
research, or was this a new analysis of existing data?)
This is field-based research. Cores were collected in late 2012 and analyzed in the lab in 2013
and 2014.
What were the key tools or instruments you used to conduct this research?
XRF scanner and radiocarbon dating.
Is this research part of a larger project or program?
We intend to develop into a larger project with NSF funding.
What are your next steps?
We submitted a letter of intent for the NSF SEES Natural Hazards program titled:
Unseen, underground and underestimated flood risks in the Mississippi River Delta
If invited, a full proposal will be submitted later in 2014.
Have you published findings or web pages related to this research? Please provide a citation,
reprint, and web link (when available).
No.
Please provide photographs, illustrations, tables/charts, and web links that can help illustrate
your research.
This research has not reached a stage to be presented. More cores are needed and the
chronology problem needs to be solved. The seed money was used to gather pilot data for a
larger NSF-funded project.
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