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Karst Inventories

There are three levels of karst inventories in BC. Each level has increasing requirements for data collection and evaluation. They are:

1. Reconnaissance

2. Planning

3. Karst field assessments.

1. Reconnaissance

Reconnaissance-level karst inventories are used to identify areas of potential karst development. These inventories have been completed for the entire province of BC.

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Figure 2-1: Reconnaissance-level inventory maps (1:250 000 scale) are available in digital format. The maps and their associated data files, are available from the Research Branch, BC Ministry of Forests.

When should reconnaissance-level inventory maps be checked?

Prior to any forest development on potential karst terrain.

What is the value of a reconnaissance-level inventory?
  • To assist in strategic planning
  • To determine whether more detailed inventories are needed
  • To help guide planning-level inventories and karst field assessments.

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2. Planning

Planning inventories (1:20 000 or 1:50 000 scale) are used to delineate karst unit boundaries, and determine the distribution and variation of karst development over a landscape or watershed. They are also used to identify the extent of karst and non-karst catchment areas.

When should a planning-level inventory be done?

A planning-level inventory could be triggered under the following circumstances:

  • Reconnaissance-level maps indicate potential karst in the area
  • There is prior knowledge of karst in or around the area
  • Karst features have been identified in or around the area.
What does a planning-level inventory evaluate?

Planning-level inventory data are used to stratify a karst unit into polygons of differing vulnerability potential which provide a preliminary indication as to the scope and intensity of karst development in the polygon. Areas mapped as moderate, high or very high vulnerability potential should have karst field assessments completed before any forestry activities commence to accurately delineate the specific characteristics of the karst.

How can planning-level inventories be used?
  • Landscape-level forest development planning
  • Guide the location and scope of karst field assessments.

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3. Karst field assessments

Karst field assessments (1:5000 or 1:10 000 scale) focus on evaluating the karst attributes of a relatively small karst area of interest (e.g., cutblock or road).

When should a karst field assessment be done?

It is recommended that karst field assessments be done prior to any road construction or forest harvesting on karst terrain. Typically they should be done prior to or during site-level planning.

A karst field assessment can be triggered under the following circumstances:

  • An area is underlain by carbonate bedrock.
  • A development is proposed on non-carbonate lands located within the contributing drainage basin of known or suspected carbonate units. (In this case, the karst field assessment would be carried out on the known or suspected karst units located downstream of the proposed cutblock.)
  • Reconnaissance-level maps indicate that an area may be underlain by karst.
  • A planning-level inventory has identified karst polygons with moderate, high or very high vulnerability potential ratings in or around the area.
  • There is prior knowledge of karst in or around the area.
  • Karst features have been identified in the area.
  • Forestry activities, such as windthrow salvage, spacing, pruning or commercial thinning are planned on an area known or suspected to be underlain by carbonate bedrock.
What does a karst field assessment evaluate?

Karst field assessments primarily evaluate surface features, but can also include subsurface evaluations if caves are encountered. Karst field assessments examine such things as:

  • The location, classification and significance of surface karst features
  • Epikarst development and soil thickness
  • Density of surface karst features
  • Karst roughness
  • Characteristics of streams
  • The inspection and mapping of caves
  • Subsurface karst potential
  • Unique or unusual flora/fauna/habitats
  • Geomorphic hazards.

The data collected during a karst field assessment are used to stratify the karst area of interest into polygons of similar karst attributes and vulnerability.

Karst vulnerability is determined during a karst field assessment using a systematic procedure that evaluates three major criteria: epikarst sensitivity, surface karst sensitivity, and subsurface karst potential. Other factors considered for assessing vulnerability include soil texture, overall karst roughness, and unique or unusual flora/fauna or habitats. Using this procedure, vulnerability ratings can be determined for each karst polygon – low, moderate, high, or very high. These ratings are used to guide appropriate forest management practices for the karst within each polygon, based on the assessed level of vulnerability (see Lesson 5).

The data from a karst field assessment also identifies “significant” surface karst features where specific protective measures (e.g., reserves) are recommended for forest operations (see Lesson 3).

Karst field assessments also identify sinking and losing streams/sinking watercourses where special riparian management considerations are recommended (see Lesson 4).

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