Unmanned aerial vehicle (UAV) technology was used to determine tidal extent in Kimages Creek, a restored tidal wetland located in Charles City County, Virginia. A Sensefly eBee Real-Time Kinematic UAV equipped with the Sensor Optimized for Drone Applications (SODA) camera (20-megapixel RGB sensor) was flown during a single high and low tide event in Summer 2017. Collectively, over 1,300 images were captured and processed using Pix4D. Horizontal and vertical accuracy of models created using ground control points (GCP) ranged from 0.176 m to 0.363 m. The high tide elevation model was subtracted from the low tide using the ArcMap 10.5.1 raster calculator. The positive difference was displayed to show the portion of high tide that was above the low tide. These results show that UAVs offer numerous spatial and temporal advantages, but further research is needed to determine the best method of GCP placement in areas of similar forest structure.

Consistent shoreline development and urbanization have historically resulted in the loss of wetlands. However, some construction activities have inadvertently resulted in the emergence of new tidal wetlands, with prominent examples of such anthropogenic wetlands found within the Hudson River Estuary. Here, we utilize two of these human-induced tidal wetlands to explore the sedimentary and hydrologic conditions driving wetland development from a restoration perspective. Tivoli North Bay is an emergent freshwater tidal marsh, while Tivoli South Bay is an intertidal mudflat with vegetation restricted to the seasonal growth of aquatic vegetation during summer months. Using a combination of sediment traps, cores, and tidal flux measurements, we present highly resolved sediment budgets from two protected bays and parameterize trapping processes responsible for their divergent wetland evolution. Utilizing a 16-year tidal flux dataset, we observe net sediment trapping in Tivoli North for most years, with consistent trapping throughout the year. Conversely, sediment flux measurements at Tivoli South reveal net sediment loss over the study period, with trapping constrained to the summer months before being surpassed by large sediment exports in the fall and early spring. The timing of the transition from sediment import to export marks the end of the invasive water chestnut growing season and the onset of the associated exodus of both sediment and organic material from Tivoli South. When sediment cores collected for this study are compared to sediment cores collected in 1996, 137Cs profiles confirm little to no sediment accumulation in Tivoli South over the previous two decades. These results support the hypothesis that water chestnut is serving to inhibit sediment trapping and facilitate sediment erosion, preventing marsh development in Tivoli South. The longevity of this dataset highlights the capacity of aquatic vegetation to regulate sediment exchange and geomorphology in enclosed bays when provided an opportunity to colonize. Results of this project provide evidence to inform the management of restoration projects in river systems with freshwater tidal wetlands, especially those affected by invasive species of aquatic vegetation. In bays where tidal sediment supply is not limited, water chestnut removal may present a viable strategy to facilitate marsh restoration.