This appendix includes a modified version of Appendix 11 in the fifth report of the Scientific Panel for Sustainable Forest Practices in Clayoquot Sound, Sustainable Ecosystem Management in Clayoquot Sound: Planning and Practices (Anon, 1995). Several physical dimensions have been altered to be consistent with other Forest Practices Code documents. The classification units changed here are intended to avoid some of the operational difficulties encountered in the field. Wherever possible, the original definitions used in the Clayoquot Sound report are retained.
The most basic division is defined by the nature of the water body, because this fundamentally determines the nature of the associated ecosystems. Lotic (streams), lentic (standing fresh water), and marine are the basic units; the latter is not considered here.
Within stream channels, the most basic division is between erodible and non-erodible channels. Erodible channels flow through either their own alluvium deposits or materials erodible by flowing water, such as lacustrine, marine and certain colluvium deposits. Non-erodible channels are non-alluvial channels — those flowing on bedrock or on sediments not normally eroded by the contemporary stream flow. This corresponds with the criterion of confinement, because an unconfined channel always flows with at least one erodible (alluvial) bank. The next most important criterion is stream gradient, because this determines important aspects of fluvial processes and morphology. A third criterion is entrenchment; entrenched channels are confined within fluvially eroded gullies or valleys of some depth. A final criterion is stream size, which influences some of the physical and biological processes.
Within the class of erodible stream channels, the definition of a "floodplain" presents some difficulty. The generic definition — the surface of a body of sediment deposited by the stream — ignores whether a change of stream regime has led to degradation and consequent development of a terrace (which is not subject to inundation). The difference is ecologically significant. A definition based on the possibility of inundation occurring needs some qualification about the frequency of inundation, but it is not practically applicable in terrain analysis procedures. The best discriminators probably are the presence of indicator plant species in the understorey and immature cumulic soils, which can be decided definitively at the stage of field checking. Adopting such discriminators requires local guidelines.
Lentic freshwater environments are divided according to whether the environment is permanently open water more than 1 m deep (a lake) or is a wetland. A second distinction is the nature of the lacustrine ecosystem: oligotrophic lakes have relatively poor nutrient status. Wetlands are further classified as fen, marsh, swamp, or bog. Another criterion is water body size. As in streams, this determines some of the physical and biological processes between the water body and adjacent land.
C — Stream channels
1. gradient less than 8 per cent
Notes: These may include fairly large channels that have degraded and now flow between terraced banks on lag armour (unconsolidated material — typically cobbles or boulders — that the stream cannot move and that is not alluvial in the current regime). An entrenched channel, as the result of fluvial erosion, is continuously confined within banks sufficiently high that overflow may not occur. Gullies, ravines, and bedrock gorges are typical entrenchment landforms.
2. gradient in the range 8-20 per cent
Notes: Class (a) streams will principally have steep alluvial fans. In this gradient range, width class (iii) streams probably are non-existent. Most debris flows stop in this gradient range.
L - Lakes
W - Wetlands
A marsh has free-standing water with emergent vegetation or remains waterlogged throughout the growing season.
A fen (minerotrophic mire) is a wetland with limited peat accumulation, maintained by groundwater and runoff. Fens often occur as shoreline wetlands peripheral to lakes, ponds, and low-gradient streams.
A swamp is a forest or high shrub mineral wetland or peat land that is periodically flooded. Swamps include sparse, open-canopy to closed-canopy forests of mixes of western redcedar, red alder, and shore pine (the latter is more commonly associated with bogs). Most of the surface is usually submerged, but there are periods when the soil may be dry and aerated.
Very poorly drained, sparsely forested swamps are characterized by western redcedar, yellow-cedar (increasingly at higher montane to subalpine elevations), red alder, crabapple, salmonberry, stink currant, skunk cabbage, and giant horsetail, all of which are culturally important. The poorly drained, closed-canopy forested swamps vary less, with predominant western redcedar and an understorey of western hemlock, both growing on raised microsites of accumulated rotting wood.
Minor vegetation includes skunk cabbage growing in wet, mucky organic materials in depressions between the drier hummocks. On the minor hummocks grow minor vegetation similar to that of mesic sites-Vaccinium spp., Comus canadensis, Hylocomium spiendens, Rhytidiadelphus loreus, etc. This latter type is properly classified as a western redcedar swamp forest, but is not generally recognized as such.
Shrub-carr is a shrub-dominated wetland, developed on mineral soils, that is periodically saturated, but rarely inundated.
A wet meadow is a herbaceous wetland that is rarely inundated. The latter two types are not waterlogged in the growing season. All foregoing types (i) to (vi) are fed by inflowing surface or groundwater.
A bog (ombrotrophic mire) is a peat accumulation that has grown above the local water table, so that the water in the upper peat is sustained by precipitation.
These definitions are consistent with the Proposed Wetland Classification System for British Columbia (Kistritz and Porter 1993).