Assessing And Recording Physical Variables - Planet WGSW-24010 User Manual

4.6 Assessing and r ecor ding physical var iables
4.6.1 Gener al method
After recording the macrophyte information re-traverse the survey length, observing and entering
details of the physical variables on the form provided in Appendix 5. The grapnel, bank
stick/ranging pole and/or underwater camera/glass-bottom bucket can be used to give an
indication of the substrate type at sites where the channel bed cannot be directly observed. Mark
the grapnel rope with 0.5m divisions and use it to determine the depth of the water, or use the
bank stick/ranging pole. It should be obvious, from grapnel throws to retrieve macrophytes, if a
change in depth has occurred within the channel.
The assessment of physical variables is NOT expected to be as precise as the macrophyte
assessments, but merely an important element which should be used to help in:
i) assessment of how comparable sites are;
ii) providing information which in the future may help in more rigorously assessing the
relationship between macrophytes and physical variables.
Orientation of the left and right banks is determined by the direction of flow. When facing
downstream, the left bank is on your left hand side and the right bank on your right hand side.
In order to ensure that data are consistent, all variables should be recorded in a manner so that
they relate to estimates in previous years. This may mean that the following categories/classes are
recorded for some physical characteristics: 1 = <5%; 2 = 5–25%; 3 = >25% as well as actual
percentages (actual percentages MUST be recorded). It is preferable to record percentages to the
nearest integer value (ie no decimal places). If a particular feature is absent, then record this as
0% (category 0): do not leave data entry spaces/boxes un-filled.
Recording of features which are present in less than 0.5% of the survey area will not usually be
required unless that particular habitat type contains the only occurrence of a scoring species.
Such recording may also be required if TDI/DQI surveys are being carried out at the same
site and the particular type of habitat is cobbles or boulders in amongst gravel or sand and
that is the only suitable substrate for sampling diatoms. In either case, a note should be
made under 'Comments' on the field sheet and care should be taken to mark the position
of such small habitat patches on the accompanying sketch map.
Quality assurance
Check, before leaving the site, that all data entry spaces/boxes have been completed as
required.
R&D Technical Report E38 51