Master of Science (MS)
Oceanography and Coastal Sciences
To achieve a sustainable Mississippi delta, the river must be reconnected to the delta through river diversions. However, the use of large diversions is hampered by opposition, partly due to resulting rapid decreases in salinity and the consequences of added nutrients. A large, intermittent river diversion would build land quickly, on the order of historic river crevasses, and infrequent operation would help to alleviate concerns regarding decreases in salinity and nutrient enrichment. This study examines a large, intermittent river diversion into the Maurepas Swamp, an upstream, forested wetland system. Objectives of this study were to (1) use a delta progradation model to estimate land grain trajectories and (2) combine these land building trajectories with ecosystem service valuation (ESV) to perform a cost-benefit analysis of the diversion project. Modelling results from the delta progradation model show that significant land building is possible in the Maurepas Swamp. For a 7079 m3/s diversion operated 16 weeks every 2 years, 138 km2 of subaerial land is built between 2030 and 2080 in the medium sea-level rise scenario, although significant uncertainty exists (-36%, +55%) due to uncertainty in basin parameters. ESV was conducted using benefit transfer, which produced a range of ecosystem goods and services (EGS) values - $1,365.91/acre/year (-76%, +152%) for restored swamp habitat and $145.73/acre/year (-33%, +100%) for restored marsh habitat - for disaster risk reduction, water quality improvement, recreation, and carbon sequestration. These EGS values were combined with habitat-type trajectories, cost estimates of the river diversion, and several discount rates to perform the cost-benefit analysis. Assuming a cost of $1.75 billion, a positive marginal benefit is realized at discount rates of about -1%, -1.6%, and -2.1% in the low, medium, and high SLR scenarios, respectively. In interpreting these results, it is important to be aware that benefit transfer is limited by the quality and quantity of relevant studies, and this study constitutes a very geographically specific usage of benefit transfer. Only a subset of the EGS provided by the Maurepas Swamp were analyzed, due to limited primary valuations within Louisiana, and error is accrued in transferring studies out of location and context.
Document Availability at the Time of Submission
Student has submitted appropriate documentation to restrict access to LSU for 365 days after which the document will be released for worldwide access.
Rutherford, Jeffrey Scott, "Examining the benefits of a large, intermittent river
diversion into the Maurepas Swamp" (2017). LSU Master's Theses. 4586.