[Riparian Management Area Guidebook Table of Contents]

Streams

In the Operational Planning Regulation, a stream is a watercourse, having an alluvial sediment bed, formed when water flows on a perennial or intermittent basis between continual definable streambanks (see Figure 2). The key to identifying a stream is evidence of fluvial processes (sands, gravel, etc.) that have been deposited by moving water. Some smaller streams may have discontinuous streambanks, particularly in the interior, although the channel should be detectable throughout the extent of the stream reach being defined.

Some existing man-made channels, excluding ditchlines, that have significant fish and wildlife values may also require the same level of protection given natural watercourses. Consult with the B.C. Ministry of Forests, BC Environment and the Department of Fisheries and Oceans to confirm the value of these man-made channels.

Classifying streams

There are six stream riparian classes designated S1 to S6. Each stream reach receives a stream riparian classification based on:

A stream reach is a relatively homogeneous section of a stream having a sequence of repeating structural characteristics (or processes) and fish habitat types. The key physical factors used to determine reaches in the field are channel pattern, channel confinement, gradient, and streambed and bank materials. Stream reaches generally show uniformity in those characteristics and in discharge. The characteristics of stream reaches are described further in the Fish Stream Identification Guidebook.

A key to the riparian classification of streams is shown in Figure 3. S1 to S4 streams are fish streams or streams in a community watershed. S5 and S6 streams are not fish streams and are not in a community watershed. The estuarine portion of a stream should be classified the same as the stream that has formed the estuary, as shown in Figure 4.

Determining fish streams

For the purposes of stream riparian classification, a fish stream means that portion of a stream that is either:

Fish presence is confirmed by the occurrence of any life phase of each species, and includes:

When stream classifications are assigned, documentation should be included that specifies whether classes are designated on the basis of either (a) an acceptable, existing fish inventory, (b) the completion of an acceptable fish inventory by the proponent, or (c) gradient criteria alone.

Approved stream inventory methods are outlined in the Fish Stream Identification Guidebook (Forest Practices Code). Supplementary information is available in the Stream Inventory Manual prepared by BC Environment, and the Stream Survey Field Guide produced jointly by BC Environment and the Department of Fisheries and Oceans.

Determining community watershed status

To determine whether a particular stream is within a community watershed and to locate watershed intakes, consult the Community Watershed Guidebook and contact the local BC Environment Regional Water Manager.

Determining average channel width

The average channel width for each stream reach partially determines the stream riparian class for that stream reach (along with fish presence and community watershed status). Once a stream is broken into reaches the following methodology can be applied to determine the average channel width for the reach. Once the average channel width has been determined, it can be used to classify the entire stream reach.

Stream channel widths vary depending on where in a watershed the channel is located. Generally, channels are relatively narrow in headwater areas and relatively wide downstream, near the mouth. The normal channel width can be greatly altered by both natural and man-induced factors. Channel width can be enlarged beyond the natural undisturbed channel width by debris torrents or flows, bank disturbances from logging operations, or by the removal of instream large woody debris (LWD).

Determination of stream riparian classes is based on normal, non-disturbed, channel widths. Be careful not to use a disturbed or unnaturally wide channel to determine the RMA. Further, recent debris torrents may cause oversized channels, resulting in a higher classification than is required.

Field indicators of channels recently affected by a debris torrent include:

If the channel displays evidence of recent debris torrents the classification of the stream should be discussed with the appropriate resource agencies.

Figure 5. Debris torrented channel photo of Landrick Creek, QCI.

Undisturbed channels

Average channel width is often obvious enough to determine the respective stream riparian classification. Where the channel width is close to a stream riparian class break (i.e., 5 or 20 m) the following methodology should be employed.

Additional stream modifiers

In addition to the six stream riparian classes there are several modifiers or conditions that do not affect classification but do influence the prescription for the stream riparian class.

Large rivers

There is a category of the S1 stream riparian class designated as a 'large river' that has, on average, over a 1 km length of a stream:

See the section "Large rivers and active floodplains," and Tables 6 and 7 for information pertaining to large rivers.

Gullies

Another modifier of stream classes is the gully. Gullies are defined as follows:

  1. overall stream gradient is at least 25 per cent; and,
  2. a reach of the stream, greater than 100 m long that has:

Streams in gullies, due to their steep gradients, are generally not fish streams. The Operational Planning Regulation requires that gullies on the coast be assessed using the Gully Assessment Procedure Guidebook. However, silviculture prescriptions and logging plans for gully management must not only address gully stability but also incorporate the wildlife provisions, pertinent to the stream class, outlined in Tables 5 through 13 in "Forest practices within the RMA, fisheries-sensitive zones, and marine-sensitive zones" of this document.

Watershed assessment procedure

A watershed assessment using the Interior Watershed Assessment Procedure (IWAP) and the Coastal Watershed Assessment Procedure (CWAP) may be required for community watersheds or watersheds with high fishery values (as determined by B.C. Forest Service and BC Environment). The results of these assessments may influence the best management practice within these RMAs. However, RMA objectives found in this guidebook should not be compromised. Consult the WAP guidebooks for the specific recommendations that apply.

Identifying large woody debris /root network dependent streams

The stability of some stream channels and streambanks is dependent on the continued presence of woody debris and live tree root networks in the channel and bank. The size of woody debris that functions in stream channels that help to maintain or create stream channel characteristics varies as a function of stream size. Logs or pieces of logs, in streams, larger than 0.5 m in diameter and greater than 1.5 m in length, are referred to as large woody debris (LWD).

LWD requirements for S1 to S3 streams are provided for by the reserve zone. Some S4 to S6 streams require the determination of the need for LWD and live tree root networks in the channel and bank.

Channels with the following features are generally dependent on LWD or live roots for channel and bank stability:

Identifying temperature sensitive streams

Streams in relatively dry, warm climates may experience significant increases in water temperature following extensive removal of streamside vegetation. Increased temperatures can detrimentally affect the timing of fish development, result in mortality of aquatic organisms including fish, and decrease the quality of water for domestic consumption. These types of streams are considered to be temperature sensitive. Management strategies (see the section "Forest practices within the RMA, fisheries-sensitive zones, and marine-sensitive zones") have generally been developed to maintain overall stream shading for fish streams.

However, some streams may require further provisions in especially sensitive portions of the province. Streams where water temperatures are especially sensitive to vegetation removal occur primarily in the southern portions of British Columbia in the IDF, ICH, PP, BG, and CDF biogeoclimatic zones. Proponents should consult BC Environment and the Department of Fisheries and Oceans for specific information on local watersheds.

Streams that have low seasonal flows, wide/shallow channels, and minimum topographic shading from the south side are most sensitive to temperature change. Streams that have a large portion of the streamside vegetation removed should also be considered temperature sensitive.

Establishing stream RMA boundaries

The riparian management area adjacent to streams extends from the top of the streambank to the greater of:

Specified slope distance

Table 1 shows the specified slope distance of the respective reserve and management zone associated with each stream riparian class. In all cases, the reserve zone extends from the top of the streambank to the specified slope distance.

The management zone extends from the outer edge of the reserve zone, where one is present, or from the top of the streambank where no reserve zone is required.

Top of the inner gorge

Where an inner gorge extends beyond the slope distances shown in Table 1, the RMA extends to the top of the inner gorge. An inner gorge is present where a stream is incised into a hillslope or valley bottom. Sidewall slopes are usually steeper than 60 per cent gradient. The top of the inner gorge occurs where the sidewall slope breaks to less than 50 per cent (Figure 7). Surface materials on the slopes of an inner gorge can be unstable and erodible.

Outer edge of the active floodplain

Where an active floodplain extends beyond the total RMA width shown in Table 1, the management zone of the RMA extends to the outer edge of the active floodplain. An active floodplain is any level area with alluvial soils, adjacent to streams, which is flooded by stream water on a periodic basis and is at the same elevation as areas showing evidence of:

Riparian vegetation present in areas that are flooded plays an important role in reducing the water transport potential of flood flows. Vegetation reduces bank erosion, loss of soils in overbank areas, and the formation and migration of stream channels. Management strategies in this portion of the RMA are directed toward retaining sufficient riparian vegetation to meet these hydrological requirements.

The management of active floodplain (Figures 8, 9, and 10) provides larger trees for the site that will retain LWD/tree root networks to:

The active floodplain is typically flooded every few years and may be less extensive than a broader floodplain that is bounded by a distinct terrace or slope break. The outer boundary of the active floodplain should be determined from field surveys. In cases where the outer edge of the active floodplain is unclear, contact the appropriate resource agencies for advice.

Non-classified wetlands and lakes contiguous to the RMA

The outer edge of wetlands and lakes that are too small to be classified and are contiguous to the RMA can be determined from on-the-ground surveys using the criteria outlined in the section "Determining the wetland area." These should be included in the stream RMA since they are often within the wetted portion of the stream during periods of high flow and often contain flood channels and pools that are important habitat for fish and other aquatic organisms. It is important to remember that the reserve zone width is determined from the top of the streambank, and that the management zone encompasses these non-classified wetlands or lakes as illustrated in Figure 11.

Classified wetlands or lakes contained within a stream RMA receive their own RMA according to their wetland or lake riparian class.


Return to top Back Forward