Ancillary Data Collection - Planet WGSW-24010 User Manual

3.4 Ancillar y data collection
Background information is needed about the macrophyte survey sites. The geological information
will only need to be researched once for each site. The pollution and channel management
information will need to be researched for each survey of a particular site. Find out what the
geological type and operational management plan is for the area to be surveyed, and the nature
of any known pollution incidents, before planning macrophyte surveys.
3.4.1 Geological and geogr aphical infor mation
The background data that should be researched from maps is rock type, altitude and slope.
Under lying geology/r ock type: the geology of a site may influence the macrophyte community
both through lithology and baseflow.
Research the rock types in the areas proposed for survey, by referring to geological maps, so the
geology of the area can be taken into account. If survey sites on a river are situated on the same
drift and solid types, it is probable that neither the lithology nor the groundwater contribution to
base flow, are causing any observed downstream change in vegetation. If the sites are on different
geological types it may be that any observed change in vegetation pattern is related in some way
to the geology of each site.
Record both drift and solid rock types. The cross-section given on the bottom of each map can
be of use in deciding on the underlying solid rock type, if it is not labelled on the map.
Altitude: site altitudes should be taken from 1:50,000 maps. It is recommended that estimates
be made to the nearest 5m.
Slope: A mean slope between the two contours either side of a site should be measured. The
slope is expressed by the following equation:-
Slope = c / x
where c = the difference in altitude (m) between contours on either side of the
site, and x = the distance (km) between the two contours as measured along the
course of the river. Use a map wheel to obtain this value.
3.4.2 Management wor k
Operational management work such as dredging and weed cutting have obvious effects on the
results of macrophyte surveys. Before planning macrophyte surveys it is useful to find out if any
work is planned or has been completed since the last survey. Surveying a site after extensive
weed cutting or dredging will reflect the damage done to the macrophyte community by the
activity. The timing of weed cutting is also important as different species grow at different rates
and reach maximum size at different times of the growing season. Thus a weed cut early in the
season will have a different effect than a later one and change the macrophyte community pattern.
R&D Technical Report E38
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