Planet WGSW-24010 User Manual page 49

4.4 Mar king the sur vey length
4.4.1 Length of r iver to be sur veyed
For all applications, the standard survey length should be 100m, with macrophyte abundance
recorded on the 9-point abundance scale C (see 4.5.5 for abundance scales). One exception is
allowed for wide and deep rivers (Box 4). Where extra information would assist in the
interpretation of data, the surveyor also has the option to undertake a 500m survey (Box 4).
When surveying a survey length for the first time, measure the actual length accurately using a
tape measure. Mark each end of the survey length with a short stake or ranging pole which is
clearly visible from the river channel.
If suitable details for relocation are included on the sketch map for subsequent surveys of the
same length at the same site, then the length may be measured out using the system of pacing
described below in conjunction with the sketch map, instead of using a tape measure. As an
alternative to pacing, a 10m rope can be used, but this requires at least two people on site to make
it an efficient method. If in any doubt, use a tape measure on each visit.
Regularly check on the number of paces needed to measure out the required survey length. This
will vary for each surveyor and should be calculated before the beginning of field work. Mark
out on the ground a 10m length and count the number of paces it takes to complete this distance.
Repeat the exercise until confident that only a small variation occurs. Multiply up the figure
obtained to determine the required number of paces for each survey length. If the error in pacing
out the survey length is more than ± 10% then the actual length should be measured with a tape
measure. This also applies where irregular pacing is anticipated due to obstructions or where
pacing could only be undertaken in the channel.
4.4.2 Width of channel to be sur veyed
The survey method covers those 'river' macrophytes contained within the 'channel area'.
Records of 'bank' species are not made unless the survey is also for conservation purposes. Non-
native and 'weed' species (Appendix 2) should be recorded.
Channel area definition:
All macrophytes seen submerged or partly submerged in the river, at low flow
levels, within the survey length. These are considered to be 'river' plants. At the
sides of the river all macrophytes attached or rooted on parts of the substrata
which are likely to be submerged for more than 85% of the year are included.
Bank area definition:
The 'bank' is defined as that part of the side of the river (or islands) which is
submerged for more than 50% but less than 85% of the time.
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