Marsh Terrace Island Design and Permitting in Virginia Beach’s Back Bay
Natural and nature-based features are a pillar of the City of Virginia Beach’s recently completed “Sea Level Wise” Adaptation Strategy which is now adopted into the City’s Comprehensive Plan. This project involves the design and permitting of a network of marsh terraces within Bonney Cove, located in Back Bay in southern Virginia Beach. This is the very first adaptation project advancing to design in implementation of the Strategy and serves as a critical element of the adaptation vision for the Southern Rivers Watershed – a mixed rural and residential area that faces complex flooding and ecosystem degradation challenges.
Marsh island restoration through terracing was identified as a particularly viable solution given the bay’s shallow bottom and the historical loss of habitat. Marsh terraces are narrow man-made islands that are arranged across areas that were historically marsh but are now open water. A series of these islands, or terraces, are typically arranged in a chevron pattern. The overall field of terraces dissipates waves and slows down water moving through the area. In turn, the calmer water allows more sunlight to penetrate to the shallow bottom, promoting the establishment and growth of marsh and seagrass so vital to the long-term health of Back Bay.
This presentation will provide an overview of this innovative, forward-looking design approach. We will highlight insights from the ongoing field data collection efforts in Back Bay, which encompass surveys of vegetation, bathymetry, underlying soil conditions, and hydrodynamics of the site. We will also describe how the field data will inform the design phase where coastal numerical models will be used to determine optimal siting and configuration of the terraces. Challenges with construction in shallow-water environments, and the need for specialized expertise and regular coordination with local, regional, state, and federal stakeholders, will be discussed. Our presentation will close with a vision of how this project fits into the more comprehensive restoration in Back Bay, and the larger Albemarle-Pamlico estuary, to strategically reduce flow through hydraulic pathways and advance restoration objectives.