Identifier

etd-01152013-123524

Degree

Master of Science (MS)

Department

Renewable Natural Resources

Document Type

Thesis

Abstract

The modern day Mississippi River Delta Plain and the Louisiana Chenier Plain have been greatly altered through anthropogenic changes to course and hydrological conditions of the Mississippi River and local rivers, most notably by levees that have excluded the Mississippi River from the delta plain. This has slowed accretion and increased land loss destroying vast quantities of marsh, endangering many coastal communities. This master’s thesis examined long-term total suspended sediment yield of four Chenier Plain rivers, total suspended sediment yield of the Mississippi River under different flow conditions, and total suspended sediment dynamics of the Atchafalaya River in relation to Atchafalaya River Delta Complex growth and Atchafalaya River Basin sedimentation. Results estimated average annual total suspended sediment yield to coastal Louisiana of 176.3 megatonnes (MT), with the Mississippi River contributing 72% and the Atchafalaya River contributing 28%. The Chenier Plain rivers contributed a negligible amount to this total, averaging annually 342,950 tonnes, with the Sabine contributing 62% to this total (213,100 tonnes), while the Calcasieu River supplied 46,850 tonnes, Mermentau River 40,200 tonnes, and Vermilion River 42,800 tonnes. The hydrograph-based approach for quantification of actual available total suspended sediment of the Mississippi River identified the rising limb of the flood pulse during Action Stage (12.1-14.6 m) and Flood Stage (14.6-16.8 m) maximized total suspended sediment with 28.9 MT supplied. Atchafalaya River Delta Complex growth rate was 2.8 km2 yr-1 (1989-2010). Both Atchafalaya River Morgan City subdelta (ARSD) and Wax Lake Outlet Subdelta (WLSD) growth rates were influenced by large floods that helped maintain positive growth rates, and tropical systems that decreased growth rates over the period. Average annual sedimentation rate in the Atchafalaya River Basin (ARB) was estimated between 30.4-79.1 mm yr-1, while total suspended sediment retention averaged 5.3 MT yr-1 (1996-2010), but interannual variation demonstrates that the ARB has reached an equilibrium and resembles a fluvially dominated system rather than lacustrine or palustrine system. Results from this study provide an exhaustive understanding of riverine sediment availability to coastal Louisiana and the impacts on coastal evolution, providing information that land managers can use to model restoration of coastal Louisiana.

Date

2013

Document Availability at the Time of Submission

Release the entire work immediately for access worldwide.

Committee Chair

Yi-Jun Xu

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