Habitat Creation in Tidal Zones: Hydrologic Issues in West Coast Applications

The creation of effective tidal marsh habitat can be streamlined using hydraulic design tools as well as through the proper identification of applicable reference sites. The frequency of inundation corresponding to vegetation zones observed at reference sites can be used to design the elevation zones of proposed tidal marshes. Seasonal fluctuations in salinity levels can affect the suitability of vegetation types in tidal zones. Project success also depends to a large extent on protection from wave action. This paper discusses issues encountered in designing habitat enhancement projects in tidal zones, including analysis of historical tidal records, application of various hydraulic modeling tools, identification of applicable reference sites, establishment of desired elevation zones for plant communities, and accounting for water quality fluctuations arising from freshet conditions. Tidal marsh habitat may be desired in areas previously outside of elevation zones suitable for vegetation establishment. In these cases, the configuration of the inlet channels and project site topography must account for the proper balance of sediment transport through tidal energy and freshwater inflow from landward sources in order to ensure a lasting project life with minimal maintenance.