Scalable Geomorphic Monitoring for Tidal Wetland Sediment Nourishments

Wetland function is, in part, controlled by geomorphic processes, and the placement of dredged material seeks to support at-risk coastal environments. However, the stability of sediments used in beneficial use of dredged material (BUDM) efforts is highly variable as a function of coastal sediment properties, which often necessitates the implementation of adaptive management decisions to ensure project success. Few studies document effective methods to monitor geomorphic processes over multiple spatial and temporal scales. Likewise, little is known about how these rapidly evolving postnourishment landscapes are utilized by wildlife. To address this, a multiplatform approach was employed at a coastal BUDM within the Delaware Bay in New Jersey. Site conditions were monitored pre-, during, and postcompletion of dredging to understand how dynamic (fluctuations in elevation, flow paths, sediment characteristics, etc.) the BUDM site was on short (days to weeks) and long (months to years) timescales. Monitoring revealed that significant elevation was gained regardless of sediment composition (sands versus fines), and sands remained mobile across the nourishment area in the months postdredging. Advantages and disadvantages of monitoring methods were evaluated to guide coastal managers on how to best capture spatial and temporal phenomena throughout the dredging process and short-term (<2 years) establishment of the wetland or shore protection feature. It was found that vibracore data can provide spatially incomplete predredging sediment characterization, and thus adaptive management methods, like adjustments to pipeline configurations, are imperative to maintain sufficient project progression. Of note, the nourished wetland was utilized frequently by native wildlife, indicating some of the intermediate benefits BUDM sites offer prior to achieving final design goals. Uncertainties related to the rates and magnitudes of geomorphic change are common during wetland nourishment, but with a scalable monitoring plan, adaptive management principles can be applied to improve success rates and reduce stakeholder concerns.