Vegetation (Floating River Vegetation) - Office of Public Works

All five Special Areas of Conservation with floating river vegetation as a conservation
aspect, namely Lough Corrib (0297), Lower River Suir (2137), River Barrow and River Nore
(2162), Lower River Shannon (2165) and the Bandon River (2171) were assessed for this study as
they overlapped with Office of Public Work arterial drainage channels. For each SAC in the study,
one or more 10km squares were selected for sampling. The main channel maintained by the OPW
within the SAC (including the limited extent of the River Nore and the River Suir) along with a
number of other channels was surveyed. Sites assessed in the broader sense assisted in the gathering
of conservation information and the understanding of floating river vegetation. Channels were
selected from an EPA database of channels, based on the Ordnance Survey Discovery vector series.
All channels within a 10km square were assigned a random number. The channels were grouped by
stream order and, starting with the highest stream order in the square, the channel with the highest
random value was selected. Each stream order present was selected in decreasing order and the
process was repeated until 10 sample sites had been selected for each square. The survey was
carried out between August and September 2006.
An exception was the Headford and River Corrib survey square. A series of channels were
selected surrounding the Black River, the main channel in the Headford square. As the Black River
is predominantly on the County Mayo side of the Lough Corrib SAC, the River Corrib was
surveyed as the main channel to conform with ecological methodology. While every attempt was
made to survey each site identified on the 10 km survey map some watercourses were inaccessible
by foot and could not be surveyed. In such cases an adjacent river of the same stream order was
chosen instead. Occasionally, alternative rivers of the same stream order were unavailable reducing
the number of sites surveyed within a 10 km square. During the course of the survey the length of
each Office of Public Works main channel was walked. Where access to sections of the main
channel within the Special Area of Conservation was possible these were also investigated for
comparative purposes.
GPS locations were determined using a hand held GPS unit (Magellan GPS 315). In the
absence of a signal, coordinates for the surveyed watercourses were obtained from an Ordnance
Survey Discovery series map. All digital images were obtained using a Canon digital IXUS 65
digital camera.
A survey of the back drains of the Ballynaclogh River maintained by the Office of Public
Works, which was reported to contain Groenlandia densa, was undertaken on the 26 th February
2007. While the primary objective of the survey was to confirm the presence of G.densa in back
drains maintained by the Office of Public Works, other information collected included habitats
present, plant distribution, general growth characteristics and the physical parameters of the
watercourse colonised by G.densa.
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