This dissertation uses two estuarine spatial
models and emergy analysis of two river
diversions within the Mississippi Delta to test
the hypothesis that natural river inputs
maximize marsh coverage and have net
societal benefits. Substantial advancements
including a higher resolution, variable
time-step hydrodynamic module, a
mass-balance sediment component, and a
marsh colonization routine, distinguished the
Mississippi Deltas Model (MDM) from the
Barataria-Terrebonne Landscape Simulation
Model (BTELSS). These advancements made
the MDM capable of simulating the
progradation of river deltas with varying river
regimes. No Action Plans (NAP), simulated by
both models, were used as a baseline of
comparison for simulations and predicted
continued land loss in the Barataria and
Terrebonne basins, and land gain in and
around the Atchafalaya and Wax Lake Deltas.
The river diversion simulation with the
BTELSS resulted in the preservation of 113
km2 of marsh and identified river diversions
as alternatives that can slow the rate of land
loss in abandoned delta lobes. In the MDM
simulations with magnified river flow and
sediment discharge increased the growth of
the deltas above the NAP rate of 2.5 km2/yr,
and reversed the trend in surrounding
marshes from land loss to land gain. Areas
with diminished river inputs due to jetty
construction experienced declines in marsh
coverage. The results from the model
simulations supported the hypothesis that
natural river inputs maximize marsh coverage.

The river diversion study demonstrated the
ability of emergy analysis to compare natural
energies and economic resources on a
common basis and identified a unique
concentration of natural energies that
characterize delta settings. By relying
primarily upon renewable energies inherent in
delta environments to produce both economic
and ecological benefits, the diversions
represent an important component of
sustainable management plans for deltaic
systems. The amount of additional emergy
exported due to the diversions outweighed the
economic costs and supported the hypothesis
that restoring riverine inputs to deltaic
marshes has net societal benefits. By
maximizing marsh coverage and producing
societal benefits, the optimization of natural
riverine inputs is a sustainable approach to
protect and restore deltaic ecosystems.

Email: martin.1130@osu.edu