Report Cover Vol I - Clare County Library

The County Clare Wetlands Survey Patrick Crushell & Peter Foss 2008
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Eroding/upland rivers
Annex 1 habitat under the EU Habitats Directive.
Natural watercourses, or sections of these, that are actively
eroding, unstable and where there is little or no deposition of fine
sediment. Eroding conditions are typically associated with the
upland parts of river systems where gradients are often steep, and
water flow is fast and turbulent. For some rivers on the seaward
side of coastal mountains, particularly in the west of Ireland,
eroding conditions persist to sea level because of comparatively
steep gradients over short distances, and high rainfall. Small
sections of other lowland rivers may also be eroding where there
are waterfalls, rapids or weirs. The beds of eroding/upland rivers
are characterised by exposed bedrock and loose rock. Pebbles,
gravel and coarse sand may accumulate in places, but finer
sediments are rarely deposited. These rivers vary in size but are
usually smaller and shallower than depositing/lowland rivers.
The unstable rocky channels of eroding/upland rivers
usually support little vegetation cover. Submerged rocks and
boulders may be colonised by aquatic mosses. Exposed rocks and
wet shaded banks may also support extensive cover of lichens and
liverworts. Higher plants are generally rare or absent except in
places where fine sediments are trapped.
Pressures from eutrophication, overgrazing, excessive
fertilisation, afforestation and the introduction of invasive alien
species are the main threat to this habitat. Almost two thirds of the
rivers assessed by the Environmental Protection Agency (EPA) are
at risk of failing to meet their environmental objectives.
Many of the streams and rivers of County Clare fit this category.
One such example is the upper reaches of Annageeragh River in West Clare.
Depositing/lowland rivers
Annex 1 habitat under the EU Habitats
Directive.
Watercourses, or sections of these, where fine
sediments are deposited on the river bed.
Depositing conditions are typical of lowland areas
where gradients are low and water flow is slow and
sluggish. These rivers vary in size but are usually
larger and deeper than those above. In a natural
state these rivers erode their banks and meander
across floodplains.
Plant and animal communities are influenced by
numerous factors including substratum type, water
force, nutrient status, water quality, channel size,
water depth, human impact, disturbance and
shade. Within a river channel there may be deep
pools, backwaters, banks or mid-channel bars of
gravel, sand or mud, in addition to vegetated
islands and fringing reed beds. The substratum of
depositing/lowland rivers comprises mainly fine
alluvial or peaty sediments. Vegetation may include
floating and submerged aquatics, with fringing
emergents in shallow water or overgrowing the
banks.
Due to their location in lowland areas, where agricultural activities are prevalent and with increased population pressures,
most of these rivers have been modified to some extent to control water flow, facilitate navigation or prevent flooding and
erosion. Canalised or walled sections of rivers, dredged or deepened sections, and artificial earth banks may occur. These
activities all alter the natural river bank and adjacent vegetation occurring along such rivers.
The principal threats to these rivers include nutrient enrichment arising from agricultural practices, human
developments along river banks and the introduction of invasive alien species, and utilization for sport and leisure activities.
There are some examples of this habitat occurring in County Clare such as the Lower River Shannon and Lower River Fergus.
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