Report Cover Vol I - Clare County Library

The County Clare Wetlands Survey Patrick Crushell & Peter Foss 2008
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Within these sources wetlands have been identified and assigned to a particular wetland category using a
variety of classification schemes, including the Annex 1 Habitats Directive system; Fossitt classification
system; the CORINE wetland classification system; together with other classification systems used in
relation to specific habitat studies (e.g. NHA survey, fens & flushes, fen classification system of Crushell
2000) and raised and blanket bog surveys.
A list of sites containing various “wetland” categories identified by these research groups, was produced
from the data sources that existed, to compile a comprehensive list of all sites that contain at least one of
the 34 wetland habitats being mapped as part of the CWS.
6.2.2 CWS Site identification and background research
On project commencement an extensive literature review was carried out on the amalgamated datasets
with the aim of identifying previously reported wetland sites throughout County Clare. Following the
literature review each site found to contain, or believed to contain one of the 34 wetland types being
recorded in this study, was added to the CWS site database and an individual site record was created.
Basic site data (county, grid reference etc.) and data in relation to the occurrence and extent of one or
more of the wetland types was recorded in relation to each site record.
Where more than one individual site occurred within a larger NHA or SAC complex, a record was created
for both the site complex and the individual sub-sites within the main site recognised by previous
researchers (see Appendix 3 for further details).
Following completion of the data recording process, any of the sites included within the CWS database for
which no wetland type had been recorded, were examined on aerial photographs. Where no wetland
areas were recorded within the site boundary the site was marked as a non-wetland site, and transferred
out of the CWS site database and stored in a non-wetland site database (a list of the non-wetland sites in
County Clare is presented in an Excel file on the CD rom accompanying this report).
For an explanation of the specific data recorded on sites see Appendix 3. This information was stored in
the CWS site database within a series of database fields thus enabling effortless searches, dataexamination
and creation of site lists during the data analysis stage of the study.
6.2.3 GIS Data compilation and GIS wetland identification
ArcView 9.2 GIS software package on a Windows Operating System was used throughout the CWS for all
mapping purposes. During the same period as the site database was being developed, GIS data-sources
were incorporated into the CWS Geographical Information System (GIS). Following the acquisition of the
relevant base-maps and aerial photographs from Clare County Council other data-sets were entered as
they became available (see Appendix 1 for list of all GIS datasets used during the CWS). See Appendix 3
for further details of methodology employed in compiling the GIS.
Soon after commencement of the survey it became apparent that the literature review would identify
principally the sites that had been previously surveyed or reported in any detail. Therefore, GIS data
compilation work was concentrated on identifying sites that may occur outside of the existing network of
designated sites (which are a major proportion of previously reported sites). The county was
systematically surveyed on a 10km x 10km basis using Colour Aerial Photographs (Ordnance Survey of
Ireland, 2007 series) avoiding existing designated sites and known lakes and rivers (which were
contained in data-sources obtained from the EPA). A minimum area of circa 1 hectare was set in the
identification of new wetland sites by GIS. As new sites were identified they were noted and a polygon
drawn encircling all identifiable contiguous wetland habitats.
Where possible, habitat types were recorded in the associated attribute table, although in many cases
this was not possible due to difficulty in determining differences between such habitats as wet grassland,
fen and marsh. In the cases where it was not possible to definitively determine the wetland type from
aerial photographic examination, the site was entered into the ‘CWS unknown wetland type’ habitat
category. In other cases a mosaic category was created to map habitat types that are impossible to
differentiate due to their close spatial association (e.g. HH3_PB3 Wet heath - Blanket bog mosaic;
HH1_HH3 - Dry - wet Heath mosaic inter alia).
It is important to note that aerial photographic surveying is a relatively crude exercise and should not be
used for any more than identifying ‘potential’ wetland types. Habitats can only be assigned (especially to
level 3 of Fossitt) by field survey and ground-truthing.
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