3 Feb 2025

Mediated Model Development for Coastal Marsh Management in the Chesapeake Bay

Purpose: The purpose of this technical note is to develop a conceptual model that describes the critical processes, stressors, and interactions that affect coastal marsh dynamics within the Chesapeake Bay, as identified by subject matter experts, and then link those factors to specific management actions. Managing coastal marshes within Chesapeake Bay involves multiple stakeholders across federal, state, local, and nongovernmental agencies. Reaching consensus among large stakeholder groups can be difficult, since each has their own perspective and requirements for management. Mediated modeling is a technique that facilitates consensus building among stakeholders and provides a transparent roadmap for decision-making. This technical note describes how mediated modeling was applied to marsh management in Chesapeake Bay. On 4–5 May 2022, The Nature Conservancy (TNC) and the US Army Engineer Research and Development Center (ERDC) Integrated Ecological Modeling Team (EcoMod) partnered for a multistakeholder mediated modeling workshop to (1) build a conceptual model that depicts the relevant processes impacting marsh dynamics, and (2) identify indicators that are necessary for tracking marsh conditions, which inform needed management strategies. This conceptual model provides the foundation for the development of a marsh management decision framework that will use indicators to identify marsh conditions that subsequently trigger management decisions.

28 Jun 2022

Two Years of Post-Project Monitoring of a Navigation Solution in a Dynamic Coastal Environment, Smith Island, Maryland

Abstract: In 2018, jetties and a sill were constructed by the US Army Corps of Engineers adjacent to the Sheep Pen Gut Federal Channel at Rhodes Point, Smith Island, Maryland. These navigation improvements were constructed under Section 107 of the Continuing Authorities Program. Material dredged for construction of the structures and realignment of the channel were used to restore degraded marsh. Following construction and dredging, 2 years of monitoring were performed to evaluate the performance of navigation improvements with respect to the prevention of shoaling within the channel, shoreline changes, and impacts to submerged aquatic vegetation (SAV). Technical Report ERDC/CHL TR-20-14 describes the first year of post-project monitoring and the methodologies employed. This report describes conclusions derived from 2 years of monitoring. While the navigation improvements are largely preventing the channel from infilling, shoaling within is occurring at rates higher than expected. The placement site appears stable and accreting landward; however, there continues to be erosion along the shoreline and through the gaps in the breakwaters. SAV monitoring indicates that SAV is not present in the project footprint, even though turbidity is comparable to the reference area. Physical disturbance of the bottom sediment during construction may explain SAV absence.

11 Aug 2020

PUBLICATION NOTICE: Post-Project Monitoring of a Navigation Solution in a Dynamic Coastal Environment, Smith Island, Maryland: Year One of Post-Project Monitoring

Abstract: In 2018, jetties and a sill were constructed by the US Army Corps of Engineers (USACE) adjacent to the Sheep Pen Gut Federal Channel at Rhodes Point, Smith Island, Maryland. These navigation improvements were constructed under Section 107 of the Continuing Authorities Program. Material dredged for construction of the navigation structures and realignment of the channel were used to restore degraded marsh. Following construction and dredging, 1 year of post-project monitoring was performed to evaluate the performance of navigation improvements with respect to the prevention of shoaling within the Sheep Pen Gut channel, shoreline changes, and impacts to submerged aquatic vegetation (SAV). Given the short period of record after the completion of the navigation improvements, it was difficult to draw conclusions regarding stability of the channel, structures, and shoreline. Therefore, this report documents methodology and baseline conditions for monitoring, except for SAV, which was found to be potentially impacted by construction. A second year of monitoring was funded by the USACE Regional Sediment Management Program for fiscal year 2020. Findings can be used to inform plan formulation and design for USACE navigation projects by illuminating considerations for placement of structures to prevent shoaling and by informing SAV management decisions.