English: Plan of the sea walls and causeways at Higham, Kent, England drawn by Flaxman C.J. Spurrell, 1885. The spot heights of the walls are in feet A.O.D. The walls are labelled a to f from oldest to newest. The old walls are old tidal defences, now obsolete. The hatched areas are high ground. At high spring tide the River Thames deposits mud on the Saltings; hence they are growing marshes. Behind the walls the marshlands are no longer growing, and are agricultural land.