On a return trip to Two Tree Island, I saw rudimentary fence-like structures in the tidal flats, odd accumulations of wood wired to bundles of sticks, lining the small creeks that run through the salt marsh. To me they looked like bits of coppiced fence, strangely situated in the mud. I have since learned that these are brushwood groynes, placed to protect or restore the intertidal zone, defined as the area of the foreshore between the average high and low water levels.
This intertidal zone plays a significant role in the structure and functioning of estuarine and coastal ecosystems. It is susceptible to natural and manmade stresses, including coastal squeeze of the foreshore in front of sea defences, erosion exacerbated by sea level rise, pollution, dredging and sedimentation. Mitigation is often required to support the natural recovery of the intertidal zone.
My interest in wetlands and the intertidal zone in the Thames Estuary dovetails with the focus of my recent Tide Line Thames project in London, which looked at the river and its architectural structures – also between the high and low tide lines.