Salt Hay Farm Restoration Design: Combining Biological and Engineering Objectives

To restore diked salt hay farms along the Delaware Bay to functional salt marshes, we had to satisfy ecological requirements within the context of engineering specifications. Because the ecosystems are complex and there are uncertainties involved in ecosystem design and construction, we agreed to use Ecological Engineering to achieve functional salt marshes with normal ecological relationships to the adjacent Bay. This means establishing sufficient conditions to start development of the ecosystem, then allowing natural processes to complete the job. Meetings between hydrologists, ecologists, and engineers developed design criteria. Tidal channels of proper shape and size to provide habitat and flows of suitable velocities were to be excavated. Tidal flooding of the marshes was to achieve a hydroperiod to allow marsh plants to flourish, requiring designs calculated from tides during the growing season. Tidal inlets were designed so that armoring would not be needed to achieve stability. We chose different techniques for two sites. At one site the channels were to be overdredged and evolution to the final condition was to be by sediment deposition. At the other site, channels were underdredged and the final condition was to be achieved by scouring.