[Interior Watershed Assessment Procedure Guidebook Table of Contents]

The interior watershed assessment procedure

The multi-agency round table

The first step of the procedure requires that a round table meeting be organized, attended by the Ministry of Forests district planner, the timber officer or district geoscientist, and the regional hydrologist, and representatives of BC Environment, Department of Fisheries and Oceans (if anadromous fisheries are involved), Ministry of Health (if a community watershed is involved), and timber, water, and range licensees.

At the first meeting, the watershed management issues of concern should be discussed and clearly defined (such as why this particular watershed assessment is required). Other issues that should be resolved at this meeting include:

The WAP applies to that portion of the watershed above the point of interest (POI). The POI in a community watershed is usually the lowest water intake in that watershed (see Appendix 3). In a fish-bearing stream it is usually the entire reach that contains fish. Once the POI is determined, the watershed above that point is divided into smaller watersheds (sub-basins) according to the guidelines provided in Appendix 3.

The process of having the round table at the outset, identifying all the watershed concerns and defining the sub-drainages of interest, is critical to the success of the entire assessment procedure. Although Appendix 3 provides a suggested method for dividing the watershed into sub-basins and determining the POI, these are only guidelines. The round table can override these guidelines at any time to make them more applicable to specific circumstances.

The watershed should be coded according to its gazetteered name and its unique numeric identifier, using the British Columbia hierarchical watershed coding system.

Level 1 analysis

Level 1 of IWAP involves the collection and collation of data that describe the basic geophysical characteristics of the watershed and the extent and location of harvesting activities in the watershed. Most of the information required can be obtained from a variety of maps-information on topography, soils, bedrock geology, and logging history. Level 1 also requires that landslides be counted from the most recent aerial photographs. Except for the latter requirements, all of the information can be extracted from a geographic information system (GIS). The use of GIS for this procedure is explained in detail in
Appendix 1.

In the analysis, perform the following tasks:

The above process is described in detail in the sections on “Level 1 analysis procedure” and “Interpretations and recommendations,” and includes forms for recording results.

The 13 impact indicators

  1. Peak flow index
  2. Road density above H60 line
  3. Road density (used for assessing peak flow changes)
  4. Density of roads on erodible soils
  5. Density of roads less than 100 m from a stream
  6. Density of roads on erodible soils less than 100 m distance from a stream
  7. Density of stream crossings
  8. Road density (used for assessing surface erosion)
  9. Portion of streams that have been logged to the streambank
  10. Portion of fish-bearing streams that have been logged to the streambank
  11. Density of landslides in the watershed
  12. Density of roads on unstable or potentially unstable terrain
  13. Portion of streambanks that have been logged on slopes > 60%

Level 2 and 3 analyses

Depending on the results of the level 1 analysis, more detailed analyses (levels 2 or 3) may be required in high hazard watersheds or sub-basins. A level 2 analysis is an overview stream channel assessment performed by an individual with some basic experience in hydrology and/or geomorphology (see the section, “Level 2 watershed assessment (channel assessment procedure),” as well as the Channel Assessment Procedure Guidebook). A level 3 analysis is a very detailed analysis, involving mostly field work. It must be performed by a watershed specialist.

Developing watershed constraints for the forest development plan

The information and interpretations provided by the assessment will be used to identify in which sub-basins certain activities are constrained over the next 5 to 10 years. From this, planning constraints will be developed and applied to the forest development plan.

Examples of the type of recommendations that might be developed are:

It is rare that all resource activity would be restricted everywhere in the watershed, but it is possible that in extremely sensitive, extremely damaged watersheds such restrictions would apply until restoration had occurred.

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