Planet WGSW-24010 User Manual page 68

Peat - dead vegetation undergoing bacterial decay in stagnant deoxygenated
water – strictly pure peat, not fine peaty deposits over more
substantial substrate.
The actual measurements given relate to the longest axis of each particle. Any rock with one or
more sides greater than 256mm long is classed as a boulder.
The particle size categories follow an adapted Udden-Wentworth system. When irregular shaped
particles are observed the longest axis length determines category assignment.
Quality assurance
Take a copy of the reference sheet provided in Appendix 5 to each site.
Check that the total of classes estimated is possible. Total up the substrata percentage cover
which should equal 100%. Check that changes in substrate composition have not occurred
due to management or flooding events.
4.6.5 Habitats
Allocate a percentage to the appropriate habitat types. Percentage categories may be recorded in
addition if required for comparison with historical data. The habitat types are POOL, RUN,
RIFFLE and SLACK, as defined below. Note that although these definitions are similar to those
used for many other biological surveys, they are NOT the definitions used for the River Habitat
Survey methodology (Environment Agency 1997).
Pool - Either a discrete area of slow flowing water, usually relatively deeper than
surrounding water, or between faster flowing stretches, as in a sequence of
riffle-pool- riffle. Pools are deep and often turbulent, and scoured during
spate flows.
Riffle - Fast flowing, shallow water whose surface is distinctly disturbed. This does
not include water whose surface is disturbed by macrophyte growth only.
Run - Fast or moderate flowing, often deeper water whose surface is rarely broken
or disturbed except for occasional swirls and eddies.
Slack - Deep, slow flowing water, uniform in character.
Quality assurance
R&D Technical Report E38 54