3.4.2. Seagrass and Saltmarches

Marine seagrass ecosystems are mainly found in shallow bays, estuaries, and coastal waters from the mid-intertidal (shallow) region down to depths of 50–60 m. The most extensive seagrass systems grow on sand and muddy ocean-beds. Ondiviela et al. [69] report that seagrass ecosystems can reduce current velocity, dissipate wave energy, and stabilize sediment—especially in shallow waters with low wave-energy environments. Restoration costs are estimated at \$106,782/ha for areas in developing countries [19].

Coastal saltmarshes occur in the intertidal zone near estuaries or lagoons and also reduce wave heights, even under extreme conditions. Creating a salt-marsh zone in front of dikes may result in a reduced dike-reinforcement task [70]. Restoration costs of coastal wetlands in general are estimated at \$67,128/ha [19].
