East Harling Internal Drainage Board
Conservation
The IDB maintains over 35 kilometres of drainage channel throughout Breckland.
Proper maintenance of these channels is of vital importance to prevent flooding,
and to provide drainage of land for agriculture. However alongside the Boards
responsibilities to drain water from the area is a responsibility to conserve and
enhance the environment and wildlife habitats.
The Board’s District includes a wide variety of habitats ranging from the dry sandy
brecks to low lying wetland meadows. Much of the area is agricultural with a
mixture of arable and stock farming. Conurbations within the Boards area include
the towns of Attleborough and East Harling and a number of villages.
Watercourses maintained by the Board are generally up to 3 metres wide and one
to two metres deep. These are natural streams and rivers rather than the drainage
channels typical of many fenland areas. Bank growth comprises alder, willow and
other fast growing trees, reed growth is common in the stream beds particularly in
areas where the stream bed is a soft, silty material. In some areas the stream bed
is formed of gravel and vegetation growth in the channel bed is sparse.
The Board carries out maintenance of its watercourses using manual labour to clear
vegetation from banks and the channels, trim trees, and remove fallen trees from
the river. Periodically machinery is used to clear sedimentation and more extensive
vegetation from the channel with spoil carefully spread on the bank top. The
Boards operatives are experienced and knowledgeable in the identification of
wildlife and their habitats and take a keen interest in country matters.
The Board carries out its maintenance works in accordance with guidelines
provided by English Nature
(1)
and DEFRA.
The IDB do not use any form of herbicides in the maintenance programme.
Works are programmed sympathetically to minimise disruption to wildlife breeding
seasons, and are based on a rotational approach to ensure that vegetation within
the channel is kept at a variety of stages of the growth cycle. Machine
maintenance is normally restricted to the stream bed with the banks left
untouched. Where possible a vegetation margin is left along the edges of the
watercourse. Many channels are only maintained on a five or ten yearly basis whilst
others may require annual manual clearing and perhaps bi-annual machine
clearing.
Machine clearing is generally carried out using a weed rake rather than a bucket
thus leaving much of the stream bed intact and preventing over-deepening of the
channel.
Manual maintenance is carried out using powered hand tools and traditional cutting
tools. Cut vegetation is removed from the channel and either burnt on the bank
top, or stacked on the bank top to provide cover for wildlife.
Tree trimming is carried out when necessary. Tree growth provides shade to the
watercourse and restricts vegetation growth, however excessive tree shading
results in insufficient growth on the banks and inhibits wildlife. Tree trimming is
carried out where necessary to allow machine access for maintenance, and to
prevent branches falling into the channel. Pollarding is carried out in preference to
removal of trees. Tree roots provide an essential part of maintaining bank stability,
removing roots will often result in banks collapsing.
The Board’s policy on watercourse maintenance has resulted in a continued
improvement in water quality and enhanced habitats.