Coastal zone management

Sourcing sediment from adjacent inlets for placement on eroded downdrift beaches is an increasingly common practice, as an inlet sources’ proximity to a placement site reduces the transportation cost of a project and is considered a beneficial use of the dredge material (BUDM). This project aimed to compare two nourishment projects using adjacent inlet sediment sources for changes in water quality, morphology, and sedimentology at two geographically similar locations in southeast Florida. In 2023, Jupiter Beach Park (Jupiter, FL) and South Inlet Park Beach (Boca Raton, FL) were nourished using sediment from the adjacent inlet system. Jupiter was nourished with sediment from the inlet’s sand trap and Boca Raton was nourished with sediment from the ebb shoal. Suspended sediment concentration (SSC) in the water column is closely associated with other properties of water including temperature, salinity, and dissolved oxygen.
A sudden increase in suspended sediment in nearshore water can be triggered by anthropogenic activity, like nourishment, as well as natural occurrences, like storms. Sampling began prior to the initiation of nourishment (February) and continued throughout hurricane season (May – November). Sediment samples were analyzed for moment method statistics (i.e., mean, standard deviation/sorting) at half-phi intervals above 63μm. Fine sediment (<63μm) was dried and weighed. Surface and bottom water samples were collected and measured for SSC, dissolved oxygen, temperature, and salinity to analyze changes in response to nourishment.

With the escalating challenges posed by global warming, sea-level rise, and natural disasters like hurricanes and tropical storms, coastal erosion has become a critical issue along the US coasts. The economic significance of U.S. coastlines, multitude of services offered by these coastal areas, underscores the critical importance of addressing the threats posed by both natural and human-induced factors that lead to erosion and coastal loss. To enhance future planning and to promote resilience of these invaluable coastal resources, it is essential to gain a comprehensive understanding of the strategies employed to mitigate coastal erosion in response to the diverse array of driving forces. A widely embraced solution to this erosion, caused by both natural forces and human activities, is beach nourishment.
Historical assessments of beach nourishment at the regional level have been conducted, however, there remains a gap in national-level analysis examining the overarching trends and the diverse factors that impact these trends. This study aims to provide a comprehensive perspective on beach nourishment practices encompassing 16 coastal states, including the top ten highly nourished states, and an additional six states selected from various coastal regions. It delves into the multifaceted factors that shape these practices, offering a holistic understanding of the beach nourishment landscape at a national level. An extensive analysis of beach nourishment trends and the influence of factors such as sea level rise, storms, hurricanes, hurricane categories, and coastal management approval years on beach nourishment activities was conducted.

The coastal system provides habitat, storm protection, and economic value. In particular, Florida’s beaches are subject to chronic coastal erosion resulting from natural and anthropogenic influences. The most common mitigation response is the nature-based solution of beach nourishment. While this method is widely considered effective, quantifying changes from the dredge and placement on the physical environment is critical to ensure best management practices. The first step in addressing the need to identify gaps in knowledge relating to natural and human-induced changes to the continental shelf, a comprehensive literature review of the US East and Gulf coast continental shelves was conducted identifying needs for more expansive sand searches, a greater understanding of storm impacts on shelf morphodynamics, planning for long-term use of offshore sediment sources, and the impact of dredging on habitats. This study then evaluated the northern Palm Beach County beaches adjacent to the Jupiter Inlet over multiple years to understand the effects of natural and human influence on the morphology and sedimentology of the beach-nearshore environment. Beach sediment was coarser near the Inlet and finer downdrift (south). Seasonal changes in the nearshore from storms decreased the grain size and eroded beaches, whereas nourishment increased grain size and expanded beach width. Influences of physical characteristics of the beach-nearshore environment on the ecosystem were examined based on two important marine species: loggerhead sea turtles and blacktip sharks. No adverse impacts from restoration activities were found on loggerhead reproductive success. However, the active 2020 hurricane season resulted in lower reproductive success metrics. The blacktip shark migration coincides with the typical nourishment construction window. High turbidity in the nearshore was documented in association with multiple nourishment events during the two-year study. The blacktip sharks were quantified in the nearshore south of the nourishment; however, whether the turbidity was influencing the shark aggregates or habitat preference remains unknown. These results support numerous benefits of beach nourishment but suggest further research is needed to evaluate how project construction may impact nearshore fauna. The findings of this study are important for coastal managers who may consider reviewing best management practices of the beach-nearshore system.

This study analyzed two different inlet management strategies being utilized in Palm Beach County and compared how the downdrift beaches were affected by those strategies throughout the year. Cross-sectional beach profiles, Digital Elevation Model comparisons, and subaerial volumetric change were analyzed for patterns in postplacement beach morphology. Trends in cross- and alongshore grainsize were also analyzed. In Boca Raton the inlet was dredged multiple times a month depending on the level of infilling and the material was placed on the beach immediately downdrift of the inlet. The downdrift beach of the Boca Raton inlet underwent a cycle of shoreline advance in the summer and shoreline retreat in the winter. It was dominated by seasonal processes and its morphologic change was the direct result of shifts in the wind and waves without having a beach more than 60 to 80 meters over the course of the study. In Jupiter, the inlet was dredged on a near annual basis and the material was placed 600m south of the inlet. The size and scope of the larger one-time annual nourishment project resulted in beach widths upwards of 120 meters. The equilibration process that followed in both the cross- and alongshore are what dominated the morphological trends experienced at the site. The results of this study should help coastal managers without current inlet management strategies, compare and overview two different successful inlet management options. For future studies, researchers should extend the monitoring period and extend profiles to the depth of closure to capture. Sediment is a valuable resource, and it’s important for best management practices to maximize benefits and protect downdrift beaches for long-term resiliency of coastal communities.

Aquatic plants and submerged aquatic vegetation (SAV) are some of the most wide-ranging species and create important habitat for fish and wildlife in many ecosystems, including highly variable coastal ecotones. Mechanistically understanding factors controlling current distributions of these species is critical to project future distribution and abundance under increasing variability and climate change. I used a population-based approach to quantify the effects of spatial and temporal variability on life history transitions of the SAV Ruppia maritima L. (widgeongrass) in the highly dynamic Everglades-Florida Bay ecotone as a model to (1) examine which life history stages were most constrained by these conditions and (2) determine how management can promote life history development to enhance its distribution, an Everglades restoration target. Ruppia maritima life history transitions were quantified in a series of laboratory and field experiments encompassing a ra nge of abiotic and biotic factors known to affect seagrass and SAV (salinity, salinity variability, temperature, light and nutrients and seed bank recruitment and competition). These studies revealed that R. maritima life history varied east to west across the Everglades ecotone, driven by multiple gradients in abiotic factors that constrained different life history transitions in distinct ways. Based on this examination, persistence of SAV populations from dynamic coastal environments is highly dependent on large reproductive events that produce high propagule densities for recruitment. Large productive meadows of SAV also depend on high rates of clonal reproduction where vegetation completely regenerates in a short amount of time. Therefore, in hydrologically variable systems, maintenance or increases in SAV reproduction is required for population persistence through recruitment. However, SAV communities that do not experience high rates of sexual reproduction are dependent on successful seed germination, seedling and adult survival and clonal reproduction for biomass production and maintenance. Seedling survival and to a lesser extent, adult survival, are bottlenecks that can limit life history transitions under highly variable hydrological conditions. To ensure long-term survival in these communities, management activities that increase survival and successful life history development through these critical stages will be beneficial. If not, SAV populations may become highly reduced and ephemeral, providing less productive habitat.

As sea levels continue to rise, the projected damage that will ensue presents a great challenge for conservation and management of coastal ecosystems in Florida. Since Juncus roemerianus is a common marsh plant throughout Florida with unique growing characteristics that make it a popular restoration plant, this study implemented a 20 week greenhouse split plot experiment to examine the effects of sea level rise on J. roemerianus and ultimately determine its tolerance ranges to salinity and inundation in a high nutrient environment. Overall, salinity level and the interaction effect of salinity level and water level had the greatest effects on measured growth parameters including average mature height, maximum height, density, basal area, root length, and biomass. An inverse relationship between increasing salinity and the measured growth variables was observed with the greatest growth and survivability in 0 ppt water, survivability and reduced growth in 20 ppt water, survivability and little growth in 30 ppt water, and nearly complete senesce in 40 ppt water. This was the first laboratory study to determine the effect of 40 ppt water on J. roemerianus. Elevated water levels resulted in higher growth variables in the 20 ppt, 30 ppt, and 40 ppt treatments while inundated water levels produced higher growth variables in the 0 ppt treatment despite previous research finding inundation to have completely adverse effects on J. roemerianus. It is likely that the high nutrient environment provided for this study is the cause for this anomaly. The results of this study have major implications for the future of coastal ecosystems that are dominated by stands of J. roemerianus in South Florida and can be used in conjunction with studies on bordering marsh plants to predict shifts in the ecosystems of Florida that are responding to sea level rise scenarios.

Water Resources (WR) agencies have recently shifted to holistic management approaches that combine the use of watersheds and ecoregions as complimentary tools. However, the classification of data is based on land used and land cover detection. In contrast, this research is concerned with inferring WR quality from the landscape using satellite imagery and aerial photography combined with collateral data. To conduct the study, three major procedures were devised: (1) construction of a classification system for regional coastal WR, (2) delineation of WR units based on the interpretation of water quality parameters (e.g. land use/cover, soil, vegetation, etc.), and (3) development and implementation of a water quality rating system. The results showed that this technique can be utilized effectively to monitor WR. The distribution of beneficial water quality was correlated with anthopogenic activities and modifications. Temporal events such as sea surface temperature had a short, but detrimental impact on water quality.

A novel, 'near-real' time technique; peptide nucleic acid chemilumiscent in situ hybridization (PNA CISH), was developed and validated for detecting, enumerating and identifying potential indicators (Staphyloccus aureus and Pseudomonas aeruginosa) of beach quality. To understand the dynamics of bacterial indicators a plethora of physical, chemical and biological parameters were tested under field and lab conditions. Escherichia coli tagged with green fluorescence protein (GFP) was used to assess the impact of wave energy and rainfall on seawater counts. PNA CISH and plate counts correlated strongly (r = 0.94 to r = 0.86). Temperature, salinity, nutrient availability and predation significantly influenced the survival of indicators. Rainfall and wave energy affected the re-suspension of bacteria from sand onto overlying water. Overall PNA CISH provides a reliable rapid method for beach monitoring. The implications of beach topography and sampling time on the numbers of Clostridium perfringens and other potential indicators are discussed. Data suggest a revision of policy for tropical sandy beaches.

Shorelines are prefigured by inherited geologic features and spatially-defined process-form relationships that require in depth study. This thesis is based on the interpretation, delineation, and analysis of coastal geomorphological features, as mapped from large-scale (e.g. 1:3600), digital, georeferenced, stereo-paired, color, aerial photography. The morphologic features identified include coral-algae reef tracts, rock reefs, sedimentary features such as bars, troughs, and sandflats, and different types of engineering works. Interrelationships between these morphologic features are analyzed using a remote sensing-GIS/MIS (Geographic and Marine Information Systems) framework, and applying interpretive approaches in the analysis of beach and nearshore morphodynamics. Sediment and wave data is used to calculate the dimensionless fall velocity (O), which combined with local geomorphology, defines beach types. Special purpose geomorphological and morphodynamic maps generated here, together with assessment of beach types and analysis of downdrift erosion provides new insights and deep understanding of large scale coastal behavior, which is of great use to management planning strategies.