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Barrier island restoration and nourishment is necessary for sustaining coastal systems worldwide. In the Mississippi River Delta Plain, the lack of sediment supply, relative sea level rise, and reworking of abandoned delta lobes promote rapid disintegration of barriers, which can contribute to mainland storm impacts. Barrier island restorations that utilize higher quality sediments (Outer Continental Shelf- OCS) are expected to exhibit higher resiliency, withstanding coastal erosion, event-induced erosion, and ongoing transgression when compared to barriers nourished using lower quality nearshore (NS) sands. Additionally, use of OCS sediments increases sediment supply by adding material to the system supporting increased barrier longevity by maintaining a subaerial footprint longer compared to NS sediments. We used the Delft3D modeling suite to study barrier geomorphic trajectories nourished using OCS/NS sands, compared with control simulations with no nourishment. Resulting morphologies from 18 simulations with forcing that included annualized forcing, storms, and SLR are evaluated and compared.

More than 45 000 dams, with the capacity to hold 15% of global river runoff, have been constructed on rivers around the world for diverse purposes including water supply, irrigation water and power. The effects of these dams on river flow are diverse and dependent upon the purpose of the dam; some dams stabilise flow to improve transportation, water access and agricultural productivity, while dams such as those for power generation create flow regimes that vary drastically over a period of hours. The benefits of regulating river flow for human needs comes with ecological costs to riverine ecosystems including local extinctions, depletion of ground water, declines in water quality and water availability. The specific ecological costs of flow regulation are dependent on how the new, regulated, flow regime differs from the natural flow regime of a river system. Regulation of flow in Australia’s lowland rivers has been undertaken to suppress the inherent flow variability and dampen flow extremes, largely to improve water access for floodplain based irrigated agriculture. Flow regulation in these systems captures moderate sized flows, releasing this stored water during periods of natural low flow. This stabilising of river flow has resulted in an increase in the abundance of introduced species and a decline in the diversity of native fish, macroinvertebrate, and littoral plant communities along with altering river channel geomorphology and decreasing water quality. These declines may be partly caused by the loss of moderate sized flows reducing lateral hydrological connectivity between terrestrial and aquatic ecosystems. In an attempt to reverse this effect, flow rules that are designed to increase the frequency of small to moderate sized flow pulses, which are mostly contained within the channel, have been introduced in many of Australian’s lowland rivers.