Revetments can take a heavy lashing from the
waves and, although they may be effective in protecting the shore-
line, they themselves may become eroded and need frequent
replacement, e.g. the concrete revetments in Mount's Bay near
Perizance in Cornwall. In some places on the north Norfolk coast
such as Overstrand, revetments have been constructed from tropi-
cal hardwoods, which are likely to need replacing after about 10
years; this is very wasteful of important natural resources.