Adam Gartelman

Ship Shoal, a large transgressive sand body on the Louisiana continental shelf, is a critical sediment source for coastal restoration. This study evaluates spatial and temporal variability in sediment grain size, percents organic matter (%OM), and carbonate (%CO₃) across the shoal crest (REF), Caminada Dredge Pit (CAM), and Terrebonne Dredge Pit (TER). Sediment samples were collected between 2020 and 2022 using box cores and analyzed for grain size, %OM, and %CO₃, with temporal and spatial patterns assessed through statistical comparisons, correlation analyses, and random forest regression models. Results show that dredged areas act as sinks for fine-grained, organic-rich sediments, with CAM consistently exhibiting the smallest median grain sizes and highest %OM, while REF maintained coarse, well-sorted sands. Carbonate enrichment reflected long-term depositional regimes, with REF exhibiting the highest %CO₃ due to the absence of dredging disturbance. Grain size and %CO₃ were identified as the strongest predictors of %OM, while %CO₃ was only weakly correlated with other sedimentary variables. Collectively, these findings demonstrate that dredge pits function as persistent repositories, with implications for benthic habitat resilience, sediment management, and coastal restoration planning. Future integration of hydrodynamic modeling with sediment transport and biogeochemical processes is needed to enhance predictive capability for managing dredged environments.

Due to high sedimentation rate up to ~1 m/year, mud-capped dredge pits (MCDP) are often considered natural laboratories for studying sedimentary processes, slope stability and the impacts of dredging activities on marine environments. Although many studies have been performed on the Louisiana shelf, there is a lack of high spatial resolution research covering the eastern, central and western Louisiana shelf to comprehensively investigate sediment infilling. Eighteen vibracores were collected from the Peveto Channel dredge pit (PC), Raccoon Island dredge pit (RI) and Sandy Point dredge pit (SP), and more than 1300 samples were analyzed to study the spatial variation in surficial sediment using statistical analyses. Our results indicate that the inner Louisiana continental shelf is silt-dominated, and there was no consistent grain size variation when comparing the sediment within the pits with that outside the pits. Skewness emerged as a prominent factor in the RI and SP, while standard deviation was the most influential in the PC. Our analysis shows also that two principal components are confirmed and account for more than 95% of the total grain size variance.

Due to high sedimentation rate of ~1 m/year, mud-capped dredge pits (MCDP) are often considered as natural labs to study detailed sedimentary processes, slope stability, and the impacts of dredging activities on marine environments. Although many studies have been performed on the Louisiana shelf, there is a lack of high spatial resolution research covering the eastern, central, and western regions of Louisiana shelf to comprehensively investigate sediment infilling in multiple MCDPs. Eighteen vibracores were collected from Peveto Channel dredge pit (PC), Raccoon Island dredge pit (RI), and Sandy Point dredge pit (SP) and more than 1300 samples were analyzed, to study the spatial variation of surficial sediment through statistical analysis. Our results indicate that the inner Louisiana continental shelf is silt dominated, sediment inside the pit could have bigger or smaller grain size compared to the sediment outside the pit, and the skewness is the most influential explanatory variable based on the absolute value of the standardized coefficients in RI and SP while the skewness is the most influential explanatory variable in PC. Our analysis shows that two principal components are confirmed and account for more than 95% of the total grain size variance.