Planet WGSW-24010 User Manual page 69

Surveyors should regularly familiarise themselves with habitat variable definitions by
consultation with other surveyors and by measurement of selected substrate types.
4.6.6 Shading
This is the percentage of the channel area affected by shading, NOT the percentage of the
bank on which vegetation causing shade stands. The shading for each bank is recorded
separately.
For the left bank, estimate the percentage of the whole channel area surveyed that is shaded
by vegetation/structures from the left bank when the sun is directly overhead (ie at 12 noon).
In a similar manner, estimate the percentage of the whole channel shaded from the right bank.
If the total shading of the channel is needed then the two figures can be added together
(theoretically this can be more than 100%). Refer to Figure 2.
When estimating the amount of shading, refer also the sketch map (4.6.9).
Three shade categories are defined: none, broken and dense.
None - no shading
Broken - some direct sunlight hits the water surface in the shade-affected area when the
sun is directly overhead.
Dense - 5% or less of the shade-affected area receives direct sunlight when the sun is
directly overhead.
Record the actual percentage in the relevant shade box. Percentage categories may be recorded
in addition if required for comparison with historical data.
0 m 20 m
À¤¤¤¤¤¤¤¤¤¤ÄÄÄÄÄÄÄÄÄÁÄĤ¤¤¤¤¤¤¤¤ÄÄÄÄÄÄÁÄÄÄÄÛÛÄÄÄÙ
¤¤¤¤¤¤¤¤¤¤
ÚÄÄÄÄÄÄÄÄÄÂÄÄÄÄÄÄÄÄĤ¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤ÄÄÄÄÄÄÄÄÄ¿
0 m 20 m
¤¤¤¤ ÛÛÛÛ
broken
Figure 2 Illustration of shading
(Only shading affecting the channel is counted, therefore in Figure 2, where shading blocks
cross the channel definition line they are counted as a half block)
The channel illustrated in Figure 2 would be recorded as:-
Shading Left bank
Right bank
R&D Technical Report E38
40 m 60 m 80 m
¤¤
40 m 60 m 80 m
dense
None 91 Broken 8
None 97 Broken 3
55
LHB
100 m Bank
River Ø
flow
100 m Bank
RHB
Dense 1
Dense 0