Make sure the pond is level! Use pegs, a straight board
and a spirit level to make sure the water level will be the same on
all sides of the pond. To prevent flooding, an overflow area
should be built beyond the edge of your pond. This overflow
area consists of a hole dug down to a free-draining layer which
you should break up, backfill with clean stones, bricks and then
cover with a filter and topsoil. The filter should be a piece of old
carpet, fibre matting or a layer of turf laid upside-down and
then put topsoil back on top. Vegetation suitable for a wet
meadow can be planted in the overflow area. If your pond is
built on uneven ground, make sure the overflow is built on the
lower end.
Background information