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01 The intertidal zone supports rich biodiversity.
02 Seawall with a terrace.
03 Seawall with intertidal pools.
shores. The limited area of this zone on walls can be increased if the wall is sloped or terraced compared to a vertical one [Figures 2, 3 & 4]. Efforts such as increasing the wall’s surface rugosity can create microhabitats that favour colonisation by varied species. These interventions do improve seawall biodiversity but to a limited extent because of the restricted zone area.
To break out of this restricted zone, we need to look at how to make the upper and drier zone of the seawall, at least up to the high neap tide level, capable of supporting biodiversity. One way is to incorporate tidal pools on the
Despite these harsh conditions presented by the uctuating tides, intertidal biodiversity ourishes because this interface between land and sea is constantly enriched with nutrients from both land and sea.
seaward side of seawalls [Figure 5]. On natural shores, tidal pools left by the receding tide support species including fish that cannot withstand exposure. A series of tidal pools of different sizes can be constructed up the seawall such that they are fully covered by high neap tides which allow free movement of mobile species and adequate exchange of water. As the tide subsides, these pools retain water and active swimming species until the next high tide twelve hours later. These pools should be sufficiently deep to prevent heating of the trapped water during the day and they should be positioned at different heights on the seawall, similar to terraced rice paddies.
On a more ambitious scale, the size of these pools can be increased so that they function as small lagoons. Storm-water discharge with terrestrial sediment can be diverted to lagoons where mangroves can be planted. Adjacent lagoons can be used to develop seagrass or coral reef habitats. The bottom of these lagoons can be raised so that the developing habitats can keep pace with
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