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broken, erosion has occurred. The runway
has a slope of 2 or 3°, but local increases
of 1/2 or 1° are accompanied by minor erosion,
the run-off cutting discontinuous gullies a
few centimetres deep. Where the slope
increases markedly, a gully nearly 2 metres
deep has been eroded.
On the steeper slope, to combat such erosion,
it has been necessary to plant trees, which
provide sufficient cover to mitigate or
negate the effect of the rain. However,
part of the slope has to be kept clear for
a bridle path. Here a deep man-made
gully has been made to one side to lead the
water down in a controlled manner. The
measure has been reasonably successful, but
care will be needed to ensure that tributary
gullies do not develop spontaneously from
the man-made gully.
Furnace Farm, Cowden, near East Grinstead
At Highdown and Wych Cross, attention was
focussed on erosion, the removal of soil.
The soil removed has to go somewhere.
Locally it goes into rivers and is deposited
on the banks during floods and in any suitable
trap such as a pond or reservoir. In the
Weald, to provide power for the iron industry,
many hammer ponds were created by damming
valleys during the Middle Ages and later.
Charcoal was used also, leading to the removal
of much of the forest cover. Erosion ensued
and most of the hammer ponds are now largely
infilled. One such pond, at Furnace Farm,
is c. 350 m long and has a dam c. 10 m high
and c. 100 m wide. The pond is now only 1
or 2 m deep for less than half of its
surface area, elsewhere it is completely