Development of Eco-friendly Seawall

At the Shin-Honmoku Pier, a new landfill wharf at the Port of Yokohama, we are developing a Eco-friendly seawall. Slits are added to caissons (concrete boxes that compose seawall) in order to calm the effects of waves and provide an internal space with different depths, we create an environment close to a reef-like seaweed bed, providing a habitat for diverse organisms to live and grow, in which natural rocks are laid in the internal space and allow the sun to shine into the internal space.

①Formation of shallow water by raising the seawall mound depth
　❏In the summer, the water tends to be hypoxic from the ocean floor to the middle layer (about 10m depth), creating a harsh living environment for organisms.
②Formation of various biological habitats with stepped slits
　❏The sea area is calmed by caisson slits with a wave-dissipating effect
　❏Create a shallow water environment with various water depths inside the caisson, with consideration for biodiversity.
③Placing natural stones inside the seawall
　❏Create an environment close to a reef-like seaweed bed, providing a habitat for diverse organisms to live and grow.
④Placing natural stones outside of the seawall
　❏Prevents droppings and carcasses of shellfish attached to the caisson wall from falling directly to the oxygen-depleted bottom and increasing the organic load.
　❏Provide a variety of water depths throughout the seawall
⑤Create public waterfront park and open to citizens
　❏Create a waterfront green area and open it up to the public for use as a sea fishing area.

Since 2019, we have been monitoring the caisson seawall at Minami-honmaki Pier in order to create an environment where marine creatures can easily inhabit and settle in the Eco-friendly Seawall. In spring 2022, we confirmed that fish (Hexagrammos otakii) spawned on the biofouling base※１ installed in the internal space of caisson.
※１　Artificial reefs using waste shells for the purpose of promoting the adhesion of marine organisms such as seaweed