Application of remote sensing video systems to coastline management problems

There is major salt marsh loss in Galveston Bay and other estuarine environments. In Galveston Bay, the causes of marsh loss include wave action, subsidence, eustatic sea-level rise, and insufficient sediment supply. To assess the relative importance of these factors in marshes of West Galveston Bay, wave action, sediment supply, and sedimentation rates were studied. Analysis of the data indicated a significant gap between the historic sediment accretion rate of 0.20 cm y−1 and the relative sea-level rise (the rate of rise of the water depth due to the combined effects of eustatic rise and subsidence) of 0.65 cm y−1. Furthermore, in 94% of the eroding marshes, where 20% exceedance wave height was less than 0.17 m, the role of wave-induced erosion was relatively small. Thus, the major cause for salt marsh loss is insufficient sediment supply. These findings indicate that in the many eroding marshes in Galveston Bay, where wave action is not the major cause of marsh loss, marsh restoration efforts ...

https://bioone.org/journals/Journal-of-Coastal-Research/volume-2009/issue-252/07-0942.1/Causes-of-Salt-Marsh-Erosion-in-Galveston-Bay-Texas/10.2112/07-0942.1.pdf

Causes of Salt Marsh Erosion in Galveston Bay, Texas

Achieving community sustainability requires understanding connected economic, social, and environmental consequences of actions that support informed choices allowing people to lead healthy, productive, and enjoyable lives, now and in the future. Designing successful sustainable development strategies reveals a tight connection between resilience, diversity, and long-lasting stability of social-ecological systems. Dauphin Island (AL) wanted to secure a resilient and sustainable future after experiencing destruction from two hurricanes. During 10 months of a transparent, all-inclusive public consultation process, culminating in a community initiated, driven, and concluded strategic plan, stakeholders designed a program of consensus-building and policy-making toward a more sustainable community with a resilient future. Facilitated stakeholder groups used the Community Capitals Framework to evaluate how various issues historically played important roles in community development. A “spiraling capital assets” model was employed to define points of decline and potential strategic improvement milestones. Resulting plans included shifting the tax base from reliance on expensive rental home lodging and property taxes to growing a more diverse, small business community emphasizing cultural heritage. As an outcome of the planning processes stakeholders examined all community assets (environmental, cultural, historic, etc.) they possessed to determine leverage points for reversing rural economic leakage patterns and promoting new local forms of valueadded economic development that protected environmental resources.

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Seeking Resiliency in the Development of Sustainable Communities

Modeling wave processes over fringing reefs with an excavation pit

Beach-nourishment requirements on the southwestern Spanish coast have led to a significant increase in offshore dredging. Following a new research line, assessment of changes recorded in physicochemical and biological parameters due to dredging and dumping operations was performed at the Cape of Trafalgar and Palmar Beach during June and July 2008. Turbidity, salinity, pH, dissolved oxygen, temperature, and suspended-sediment data were collected at 10 stations. At the end of the study, a three-campaign monitoring program was implemented for 1 year to assess the possible effects on biological communities and sediment properties. The relevant results, such as the average extent of the sediment plume (<400  m) and its persistence in the environment (<10  min), are discussed in this paper. A precise correlation between turbidity and suspended sediments and the recovery time of ecological balance were also established. Furthermore, minimal and reversible effects caused by dredging and dumping operations in thi...

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Turbidity and Other Effects Resulting from Trafalgar Sandbank Dredging and Palmar Beach Nourishment

A methodology is presented for predicting the impacts of nearshore dredging on shoreline change, using numerical models for waves, currents, and shoreline change. The dredge pit, outside of the surf zone, was assumed to be steady state, but alters waves reaching the surf zone. The methodology accounts for the transformation of directional wave energy spectra due to spatial gradients in both mean currents and bathymetry, wind inputs, and energy dissipation via several mechanisms. The wave transformation model SWAN (Simulating Waves Nearshore) was used to simulate waves at Folly Island, S.C., which served as the test case. Wave model results were validated using short-term field measurements at three locations. Longer-term (1 year) simulations were driven using hindcast wave and wind data. Velocity fields and tidal stages were simulated using the hydrodynamic model Environmental Fluid Dynamics Code in two-dimensional mode, after calibrating with field measurements. Wave model results were used to estimate longshore sediment transport and shoreline change due to longshore gradients of the longshore sediment transport rate. Empirical sediment transport coefficients were chosen to match model results to measured beach volume changes derived from beach profile data. The calibrated model was then used to predict impacts of dredging on long-term shoreline change. Results reproduced observed trends of erosion and accretion along approximately 90% of the shoreline.

Fairlight Fehrenbacher

Papers

Nearshore Impacts of Dredging for Beach Nourishment