Beach nourishment

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.

As climate change threatens with sea-level rise and more storms, increased erosion could increase the need for beach nourishment. Alterations to sand characteristics may result in changes to the sea turtle nest microenvironment, impacting the temperature and oxygen levels which may affect hatchling performance. In this study, leatherback, loggerhead, and green nests were sampled from two sites with different sand characteristics in Juno Beach, Florida, USA. Gas exchange was higher in green turtle nests with a greater mixture of sediment. Darker sediment elevated nest temperatures. Finer sediment and a greater mixture of sediment in leatherback nests elevated the nest temperatures; conversely finer sediment, and a greater mixture of sediment decreased loggerhead and green nest temperatures. Elevated nest temperatures reduced leatherback, loggerhead, and green turtle hatchling performance. Understanding the relationships between beach composition, nest environment, and hatchling performance will aid management decisions essential to sea turtle conservation.

For the last several decades, beach nourishment has been a widely implemented erosion mitigation strategy along many developed coastlines. Measuring subsequent patterns of erosion and accretion can help elucidate local sediment transport trends, improve time scale predictions of profile equilibration, decrease renourishment intervals, and adjust future engineering design of nourishments. This study evaluates the morphologic evolution of two beach nourishment projects (e.g., characterized as a full and partial nourishment) at the same location in Boca Raton, Florida using time series beach profiles, surface sediment samples, and wave data. More than 85% of sediment volume was retained within the full nourishment six months after project completion, compared to 50% retained eight months after completion of the partial nourishment. Wave energy largely influenced immediate post nourishment change. Profile equilibration was controlled by high-energy events (i.e., hurricanes) for both nourishments.

Jupiter Island is a barrier Island on the central East Coast of Florida whose beaches are subject to severe erosion. At intervals of several years, lost sand is replaced by the addition of sand ("renourishment") from other locations. In this study, I determined the effect of sand replacement on sea turtle nesting activity, and on the survival of nests placed on renourished and an adjacent natural beach. Renourishment caused a reduction in nesting activity by the turtles, which lasted about two years. Thereafter, turtle nesting on renourished and control beaches was similar. There were no differences in nest survival between the two sites. Renourishment prevents the loss of beach and shoreline property, but is not necessarily beneficial to sea turtles.