Search Results (5)

Coastal vegetated ecosystems, including tidal marshes, vegetated dunes, and shrub- and forest-dominated wetlands, can mitigate hurricane impacts such as coastal flooding and erosion by increasing surface roughness and reducing wave energy. Land cover maps can be used as input to improve simulations of surface roughness in advanced hydro-morphological models. Consequently, there is a need for efficient tools to develop up-to-date land cover maps that include the accurate distribution of vegetation types prior to an extreme storm. In response, we developed the RUSH tool (Rapid remote sensing Updates of land cover for Storm and Hurricane forecast models). RUSH delivers high-resolution maps of coastal vegetation for near-real-time or historical conditions via a Jupyter Notebook application and a graphical user interface (GUI). The application generates 3 m spatial resolution land cover maps with classes relevant to coastal settings, especially along mainland beaches, headlands, and barrier islands, as follows: (1) open water; (2) emergent wetlands; (3) dune grass; (4) woody wetlands; and (5) bare ground. These maps are developed by applying one of two seasonal random-forest machine learning models to Planet Labs SuperDove multispectral imagery. Cool Season and Warm Season Models were trained on 665 and 594 reference points, respectively, located across study regions in the North Carolina Outer Banks, the Mississippi Delta in Louisiana, and a portion of the Florida Gulf Coast near Apalachicola. Cool Season and Warm Season Models were tested with 666 and 595 independent points, with an overall accuracy of 93% and 94%, respectively. The Jupyter Notebook application provides users with a flexible platform for customization for advanced users, whereas the GUI, designed with user-experience feedback, provides non-experts access to remote sensing capabilities. This application can also be used for long-term coastal geomorphic and ecosystem change assessments. Full article

To assess the impact of the marine environment on the community of fish eggs in Daya Bay, we collected fish egg samples across four seasons during 2022. A total of 51 species of fish eggs were gathered. The fish egg community exhibited significant seasonal and spatial variations. The number of fish egg species was highest in spring and lowest in winter, while overall abundance peaked during summer. The abundance of eggs from large economic fish (Sparidae) showed a declining trend; however small pelagic fish (Leiognathidae, Engraulidae) have become dominant over time. Spatially, higher abundance is observed in the inner bay compared to the outer bay, particularly around coastal bank waters, near islands and reefs. Additionally, environmental factors and geographical location significantly influenced the fish egg community. For instance, Stolephorus continentalis and Photopectoralis bindus demonstrated a significant positive correlation with both temperature and water depth; conversely, Acanthopagrus schlegelii exhibited a negative correlation with water temperature. Full article

Coastal highways along narrow barrier islands are vulnerable to flooding due to ocean and bay-side events, which create hazardous travel conditions and may restrict access to surrounding communities. This study investigates the vulnerability of a segment of highway passing through the Pea Island National Wildlife Refuge in the Outer Banks, North Carolina, USA. Publicly available data, computational modeling, and field observations of shoreline change are synthesized to develop fragility models for roadway flooding and marsh conditions. At 99% significance, peak daily water levels and significant wave heights at nearby monitoring stations are determined as significant predictors of roadway closure due to flooding. Computational investigations of bay-side storms identify peak water levels and the buffer distance between the estuarine shoreline and the roadway as significant predictors of roadway transect flooding. To assess the vulnerability of the marsh in the buffer area, a classification scheme is proposed and used to evaluate marsh conditions due to long-term and episodic (storm) stressors. Marsh vulnerability is found to be predicted by the long-term erosion rate and distance from the shoreline to the 5 m depth contour of the nearby flood tidal channel. The results indicate the importance of erosion mitigation and marsh conservation to enhance the resilience of coastal transportation infrastructure. Full article

Coastal dunes arise from feedbacks between vegetation and sediment supply. Species-specific differences in plant functional morphology affect sand capture and dune shape. In this study, we build on research showing a relationship between dune grass species and dune geomorphology on the US central Atlantic Coast. This study seeks to determine the ways in which four co-occurring dune grass species (Ammophila breviligulata, Panicum amarum, Spartina patens, Uniola paniculata) differ in their functional morphology and sand accretion. We surveyed the biogeography, functional morphology, and associated change in sand elevation of the four dune grass species along a 320-kilometer distance across the Outer Banks. We found that A. breviligulata had dense and clumped shoots, which correlated with the greatest sand accretion. Coupled with fast lateral spread, it tends to build tall and wide foredunes. Uniola paniculata had fewer but taller shoots and was associated with ~42% lower sand accretion. Coupled with slow lateral spread, it tends to build steeper and narrower dunes. Panicum amarum had similar shoot densities and associated sand accretion to U. paniculata despite its shorter shoots, suggesting that shoot density is more important than morphology. Finally, we hypothesize, given the distributions of the grass species, that foredunes may be taller and wider and have better coastal protection properties in the north where A. breviligulata is dominant. If under a warming climate A. breviligulata experiences a range shift to the north, as appears to be occurring with U. paniculata, changes in grass dominance and foredune morphology could make for more vulnerable coastlines. Full article

A geographic information system (GIS) was used to introduce and test a new method for quantitatively characterizing topographic change. Borrowing from classic Newtonian mechanics, the concept of a body’s center of mass is applied to the geomorphic landscape, and the barrier island environment in particular, to evaluate the metric’s potential as a proxy for detecting, tracking and visualizing change. Two barrier islands along North Carolina’s Outer Banks are used to test this idea: Core Banks, uninhabited and largely-undeveloped, and Hatteras Island, altered by the presence of a protective dune system. Findings indicate that for Core Banks, the alongshore change in the center of mass is in accord with dominate littoral transport and wind conditions. Cross-shore change agrees with independent estimates for the island migration rates. This lends credence to our assertion that the mass center metric has the potential to be a viable proxy for describing wholesale barrier migration and would be a valuable addition to the already-established ocean shoreline and subaerial volume metrics. More research is, however, required to demonstrate efficacy. Full article