Future conditions of coastal Louisiana are highly uncertain due to the dynamic nature of deltas, climate change, tropical storms, and human reliance on natural resources and ecosystem services. Managing a system in which natural and socio-economic components are highly integrated is inherently difficult. Sediment diversions are a unique restoration tool that would reconnect the Mississippi River to its deltaic plain to build and sustain land. Diversions are innately adaptable as operations can be modified over time. An expert working group was formed to explore how various operational strategies may affect the complex interactions of coastal Louisiana’s ecological and social landscape and provide preliminary recommendations for further consideration and research. For example, initial operations should be gradually increased over 5 to 10 years to facilitate the development of a distributary channel network, reduce flood risk potential to communities, limit erosion of adjacent marshes and reduce stress to vegetation and fish and wildlife species. Diversions should operate over winter peaks to capture the highest sediment concentration, reduce vegetation loss while dormant, and reduce detrimental effects to fish and wildlife. Operations during the spring/summer should occur over shorter periods to capture the highest sediment load during the rising limb of the flood peak and minimize impacts to the ecosystem. Operational strategies should strive to build and sustain as much of the coastal landscape as possible while also balancing the ecosystem and community needs.

This paper depicts a simulation-based assessment of sediment quality on the performance of dedicated dredging projects for barrier island restoration in coastal Louisiana, USA. The research involved the development and integration of two sub-models. In the first, geomorphic modeling was used to simulate sediment transport dynamics within a proxy barrier island template over a 50-year trajectory. The template was assumed to be nourished with one of two sources of dredged material: nearshore (NS) sediments of lower quality (smaller grain diameter, higher organic fines); or higher quality sediments from distal sources located on the Outer Continental Shelf (OCS). In the second model, agency project records and commercial bids were used to estimate project construction costs as a function of dredge material quantity, transport distance, and project target elevation. These sub-models were coupled within a net present value framework from which average annual break-even values for ecosystem services (EBEV) were derived as an efficiency metric for comparing the economic performance of NS- and OCS-sourced projects. Results indicate that in some cases, the physical resiliency afforded by even small increases in sand diameter (+4 μm d50) can translate to greater long-term economic viability (lower EBEV) for OCS-sourced sediment transported over longer distances. Moreover, projects constructed with much higher diameter OCS sediment (+44 μm d50) with low fines and transported over relatively long distances (200 μm, 5% fines, 15-20 miles) were found to be more cost-effective than all comparably-sized projects constructed with lower quality NS sediments obtained from proximal sources (156 μm, 20% fines, 3-5 miles). For some comparisons, this quality advantage yielded a lower EBEV for OCS-sourced projects with transport distances exceeding 30 miles. Under storm-punctuated simulations, these quality advantages were more pronounced, with greater physical and economic implications for earlier (Y₅) versus later (Y₂₀) occurring storms. Budgeting for dedicated dredging projects has traditionally centered on the value of sediment as a commodity, with a focus on material placement cost. The findings of this study, however, indicate that a more comprehensive accounting of sediment quality and performance is required to maximize the economic efficiency of coastal restoration spending.

The coastal zone of Louisiana contains more than 3 million wetland acres and has the highest acreage of salt marsh of any state. However, Louisiana accounts for 80 percent of the nation’s coastal land loss. The loss of Louisiana’s coastal wetlands results in changes in economic and ecological benefits on local communities. The purpose of the study is to investigate the factors that motivate private coastal landowners to participate in income-generating activities and the level of income derived from their coastal wetland parcels and to gauge their opinion of potential policy instruments for coastal wetlands stewardship. A double-hurdle model was applied to econometrically identify the determinants on the participation and level of participation in income-generating activities using data collected from a sample of coastal wetland owners. The results based on the estimated parameters and marginal effects revealed that decisions to participate and the level of participation are related to physical characteristics of the wetland and socioeconomic characteristics of the landowner. For example, the type of wetland is the primary factor influencing the decision to participate and the level of participation. In addition, understanding the landowner’s attitude toward wetland restoration program provides the opportunity for policymakers to better evaluate current and potential policies for coastal management in Louisiana.