Planet WGSW-24010 User Manual page 71

4.6.7 Water clarity
Record the actual percentage of the channel in each water clarity category. More than one
category may be present as a survey length may be clear in the shallow margins and progress
through cloudy to turbid as the water depth increases. Percentage categories may be
recorded in addition, if required for comparison with historical data.
Clear - Channel substrate is clearly visible at all depths, as are macrophyte
species.
Cloudy - Slightly discoloured with a moderate load of suspended solids and partially
reduced light penetration. All clumps of macrophyte species can be
located on the substrate of the river channel but the view of them is
partially distorted. A small piece/single shoot of a macrophyte species
may be missed.
Turbid - Strongly discoloured, carrying a heavy load of suspended solids and having
greatly restricted light penetration. The channel bed is obscured and
submerged macrophyte species are indistinguishable from substrate and
water. This will lead to a reduction in accuracy and efficiency of the method.
Quality assurance
Consider the clarity throughout the length while surveying and assign percentages
accordingly. It is likely that the same category will apply throughout a 100m survey length.
4.6.8 Bed stability
The following 4 classes are used to define bed stability:
Solid/firmly bedded - eg bedrock/compacted clay, increased flow has little effect
Stable - eg boulders/pebbles/gravel, unlikely to be significantly altered by
increased flows
Unstable - eg gravel/sand/silt/mud, likely to be dislodged by increased flows
Soft/sinking - eg deep silt/mud, makes channel unwadeable, bank stick penetrates
easily into substrate.
Record the actual percentage of the channel in each of the above bed stability categories.
Percentage classes/categories may be recorded in addition, if required for comparison with
historical data.
4.6.9 Sketch map
The purpose of the sketch map is to enable future relocation of the survey length and is not a
record of individual surveys. It is not necessary to make detailed plans of each survey.
R&D Technical Report E38 57