Introduction

Overview of the watershed assessment procedure

The Forest Practices Code Regulations require that a WAP be completed for all community watersheds and for all watersheds with high value fisheries that are jointly requested by the Ministry of Environment, Lands and Parks and the Ministry of Forests. The results of the WAP are to be submitted by forest licensees with a forest development plan proposal. The forest development plan must be guided by the results of the WAP, to ensure that timber harvesting does not negatively affect watershed values.

The assessment of hydrological impacts focuses on: 1) the potential for changes to peak flows; 2) the potential for landslides; 3) the potential for accelerated surface erosion; and 4) the anticipated changes to the channel riparian buffer. From the results of a WAP, recommendations can be made, aimed at preventing or mitigating the impacts of forestry-related activities in the watershed. The recommendations may call for such actions as modifying future harvest layout or scheduling, recognizing sensitive zones, or adopting specific practices in the watershed.

The watershed assessment procedure is most suitable for watersheds between 500 and 50 000 ha in area (5–500 cubic km).

The WAP has three levels of analysis:

Level 1:

A reconnaissance level analysis intended as a coarse filter to identify watersheds that may have impacts from the cumulative effects of past forest harvesting or planned future forest harvesting

Level 2:

An overview stream channel assessment performed by someone with basic experience in hydrology and/or geomorphology (see Channel Assessment Procedure Guidebook)

Level 3:

A very detailed analysis performed by a watershed specialist, involving mostly field work. The work is guided by the results of the level 1 and level 2 analyses.

To accommodate physiographic and biogeoclimatic differences between the coast and the interior of the province, two assessment procedures have been developed: the coastal watershed assessment procedure (CWAP) and the interior watershed assessment procedure (IWAP) (using the differentiation between coast and interior as given in the Forest Practices Code). Figure 1 shows the steps involved in conducting either a CWAP or an IWAP.

This guidebook explains, step by step, how to complete a level 1 analysis for the CWAP. “The coastal watershed assessment procedure” gives an overview of the procedure (Figure 1). “The level 1 analysis procedure” then describes in detail how the level 1 analysis should be conducted, and includes the forms recommended for use in recording results. Finally, “Interpretations and recommendations” explains how the results of the analysis should be interpreted and used to make recommendations.

Figure 1. Flowchart for completing a watershed assessment procedure.

When to do a watershed assessment

Because there are more watersheds to which the WAP could be applied than could be completed in one year, resource managers must prioritize watersheds for analysis. The WAP, intended to assess potential cumulative impacts from past or proposed forest practices, is thus best applied where a potential for cumulative impacts exists. Watersheds with this potential include those in which forest development is proposed for the next 5-year period, and in which:

• at least 20% of the watershed's area will have been logged during the past 25 years (including the 5 years of the proposed development plan)
• a significant number of landslides are known to have occurred
• stream channel stability problems are evident.

Careful prioritization and selection of watersheds for assessment will ensure that operational plans can continue to be approved over the approximately 5-year period it will take to complete the level 1 assessments.