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Overview Assessment

Aims of the Overview Assessment
Steps in the Overview Assessment
Output from the Overview Assessment

Aims of the Overview Assessment

The focus of the overview assessment is:

  • to identify riparian areas that have been previously logged.

The objectives of the overview assessment are:

  • to identify within the previously logged riparian areas, areas with known or suspected impaired functions
  • to identify sites for Level 1 field assessment.

The overview assessment uses existing or easily obtained information to provide a preliminary indication of impaired riparian function at specific sites in the watershed. The results of the overview assessment will direct subsequent field surveys to those areas of the watershed where riparian function impairment may require restoration. If location of sites and extent of impairment are already known, you may be able to proceed very quickly to Level 1 field surveys after summarizing the existing data. Most overview assessments should only require from 2 to 10 person-days of effort, depending on the extent of area to be covered.

Note that the results of the initial watershed assessment procedure, the channel conditions and prescriptions assessment procedure (Technical Circular No. 7) and the fish habitat assessment procedure (Technical Circular No. 8), if already completed, may help identify areas of special concern in advance of the overview RAPP.

Steps in the Overview Assessment

The steps in the overview assessment are:

  1. Identify and delineate the watershed of interest.
  2. Assemble existing information. Materials to review include a combination of:
    • air photos (historic)
    • air photos, (recent), preferably low level 1:5000 scale and in colour, especially where access is limited
    • topographic maps
    • licensee files, forest cover and TRIM maps
    • other MOF maps/reports, opening files
    • other WRP reports
    • interviews with local MOF and MELP personnel, forest licensee personnel.
  3. From the existing information, following the instructions for Form 1 (Appendix 7):
    1. Identify harvested areas, with primary focus being harvested areas near or adjacent to S1-S3 streams, unless directed otherwise by the contracting agency.
    2. Categorize harvested areas by distinct riparian vegetation types, which at the overview stage will be based on stand structural stage and tree type (e.g., PSc, pole sapling - coniferous; MFm, mature forest-mixed conifer/deciduous; SH, shrub-herb) (also refer to glossary). Dominant species can be added if the data are available, but this will seldom occur at the overview stage.
    3. Record past harvesting and restocking history and any other readily known or observable disturbances (e.g., erosion and slides).
    4. Identify priority sites for Level 1 field assessment.

Overview Form 1 Instructions

Use the following instructions to complete Form 1 (also refer to completed form example in Appendix 7):

Watershed Name/Code: Identify the watershed by its gazetted name and hierarchical watershed code. Refer to the Gazetteer of Canada for British Columbia (Anonymous 1985) for official names. Obtain the watershed code from the MELP Watershed Dictionary (consult regional WRP staff). Note that sub-basins may have their own codes. If standard watershed codes have not been assigned to the stream, follow the guidelines in the Fish-stream Identification Guidebook to assign an interim locational point to the stream mouth.

NTS Map: Record index number of the NTS (1:50 000 scale) or BC Geographic Survey (BCGS 1:20 000 scale) map that depicts the downstream boundary of the stream reach or sampling site.

Air Photo: Record the flightline and air photo number that depicts the stream reach or sampling site.

Reach # (Reach number): A reach is a relatively homogeneous section of stream having a repetitious sequence of physical characteristics and habitat types. Reach numbers are assigned in upstream ascending order starting from the mouth of the stream. Delineating reaches is optional if doing only a riparian assessment, but is strongly recommended if also completing a channel condition, or fish habitat assessment (WRP Tech. Circs. 7 and 8, respectively).

Polygon # (Polygon number): A polygon is an area of vegetation that appears on air photos to be distinct from the adjacent vegetation. Using an omnichrome pen and mylar overlay, draw the boundaries of each polygon in the riparian zone of your study area.

Stand Structure: Identify and record the stand structure (SSt) within each polygon. Classification should include one of the following (see Glossary for more details):

INIT (initial succession) - earliest successional (developmental) stage (0-1 yr)

SH (shrub herb) - early successional stage (1-20 yr)

PS (pole sapling) - trees >10 m tall, densely stocked (10-40 yr, depending on species (e.g., alder is PS stage at 10-15 yr)

YF (young forest) - forest canopy forms distinct layers (30-80 yr)

MF (mature forest) - Canopy comprised of mature trees with second cycle of shade-tolerant trees establishing in understorey (80-250 yr)

OF (old forest) - old, structurally complex stands of mainly shade tolerant and regenerating trees (250+ yr).

If it is possible to pick out tree species and dominance from air photos and/or forest cover maps, record these in the same column. Otherwise, include only stand structure. If only 1:15 000 to 1:20 000 air photos are available, it may only be possible to identify stand structure and whether it is deciduous tree dominated (d) (>75% tree cover); coniferous tree dominated (c) (>75% tree cover); or mixed (m) deciduous/coniferous tree species (neither deciduous nor coniferous trees account for >75% cover) (e.g., PSc refers to a "conifer dominated pole-sapling stand).

Tentative RVT #: Based on stand structure as recorded in the previous column, assign a riparian vegetation type (RVT) number for each polygon, keeping in mind that several different polygons may contain the same RVT. At this time, the RVT numbers are tentative since they will likely be adjusted during the field visit at the Level 1 assessment, with the final RVT labels recorded on Form 3 (the Level 1 assessment summary form). The final RVT labels will be based on stand structure and tree species, and may also include a recognition of understorey vegetation types. One would also expect different RVT numbers in different BEC zones and subzones. The Overview stage, being an office-based assessment can only provide a broad-brush RVT description.

Stream Class: Identify the stream class (Code S1-S6 stream). A key to the riparian classification of streams was shown previously in Table 1.

Harvesting History: Using sources such as forest cover maps, silvicultural history (ISIS database from MOF), and local knowledge, record known harvesting history such as harvest date, age class, silviculture treatments, and year of site preparation or replanting.

Other Disturbances: If a major disturbance other than harvesting has occurred, record it. Disturbances include fire, insect or disease infestation, flooding, surface erosion, slope failure, overgrazing and presence of roads, bridges and culverts.

Priority for Level 1: Selection of sites recommended to proceed to a Level 1 field visit and assessment should be based on the following:

  • information gathered on stand structure, harvest history and extent of proper functioning condition (Figure 3)
  • other disturbances (e.g., fire, erosion, wind throw)
  • high fisheries values
  • expected level of benefit to the watershed, and likelihood of restoration success.

Output from the Overview Assessment

Output from the overview assessment includes the following:

  1. Brief discussion of methods used in the overview assessment.
  2. Form 1 data (Appendix 7).
  3. Mapping and map overlays of harvested riparian polygons in study area.
  4. Identification of known or suspected impaired polygons.
  5. A brief discussion of potential impairments.
  6. Recommended sites for Level 1 field data collection.

In some cases, a recommendation for no further assessment may be made based on, for example, knowledge that sufficient regeneration is already occurring. However, confirmation of this would likely require a brief field reconnaissance by an experienced riparian vegetation specialist.

Figure 3. Stand structure stages on pathway to desired future condition.

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