Lesson 8: Karst Inventories and Resource Information

On this page

• Lesson objectives
• Reconnaissance-level karst inventories
• Planning-level karst inventories
• Karst field assessments
• Remote sensing and karst
• Test your knowledge

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Lesson objectives

Karst inventories provide valuable information for forest management planning. The Karst Inventory Standards and Vulnerability Assessment Procedures for British Columbia (RISC 2003) sets out provincial standards and procedures for completing karst inventories at three general mapping scales. Each karst inventory level has increasing requirements for data collection and evaluation. The hierarchical approach to evaluating karst terrain in B.C. begins at the broader reconnaissance level and progresses through an intermediate planning level to the more detailed karst field assessment (KFA). Broader scale karst inventories cover wider geographical areas but provide lower levels of accuracy and detail.

By the end of this lesson, you should be able to:

• Describe the purpose of each of the three levels of karst inventories
• Name the key provincial training course recommended for persons conducting KFAs
• Describe how LiDAR can assist in completing KFAs

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Reconnaissance-level karst inventories

What are reconnaissance-level karst inventories?

Reconnaissance-level karst inventories are used to identify areas of potential karst development at a regional scale (1:250,000 scale).

What are the purposes/objectives of reconnaissance-level karst inventories?

Information from reconnaissance-level karst inventories can be used to assist with strategic planning (for example, to support regional and sub-regional land-use plans or tree farm licence management plans).

Karst inventory data collected at the reconnaissance level can also help direct planning-level karst inventories and KFAs.

The karst potential area polygons (described below) generated at the reconnaissance karst inventory level can support inventories at the more detailed planning and operational levels by indicating the potential presence or absence of karst when no other data are available.

What triggers when a reconnaissance-level karst inventories is required?

Reconnaissance-level karst inventories are normally done in response to a need for karst and karst potential mapping to support strategic planning or resource inventory needs at provincial, regional or sub-regional scales.

How are reconnaissance-level karst inventories done?

Reconnaissance-level karst inventories are essentially office-based analyses of bedrock geology maps. GIS software and algorithms are used to predict areas of karst potential. These are the map areas likely to host karst. A map polygon generated at this karst inventory level defines a karst potential area (KPA).

KPAs highlight areas where karst may occur. The likelihood of karst for a KPA is ranked as L–low, M–moderate or H–high. The predicted level of karst development intensity in these areas is ranked as P–primary, S–secondary or T–tertiary.

Reconnaissance-level karst potential data can be progressively refined using new bedrock geology maps and other more recent data.

Who carries out reconnaissance-level karst inventories in B.C.?

Land-use planners can initiate reconnaissance-level karst inventories for any areas of interest. The inventory work is typically carried out by a geoscientist with some karst knowledge and experience.

The Research Branch of the Ministry of Forests commissioned a province-wide reconnaissance-level karst inventory which was completed in 1999. The inventory covers 100% of B.C. in 87 map sheets. The Forest Analysis and Inventory Branch of the Ministry of Forests is the provincial custodian of the currently available reconnaissance-level karst potential datasets.

Are reconnaissance-level karst inventories available to the public? If so, how can they be accessed?

The 1999 reconnaissance-level karst potential mapping can be downloaded in digital format from the B.C. Data Catalogue or viewed through web mapping applications such as iMapBC or Forest Mapview.

iMapBC is an online map viewer that allows for working with and viewing data in an interactive environment and has basic GIS capability. It has simple query and analysis tools. You will find the karst potential digital map layers in the Mining and Petroleum folder.

Forest MapView is a web mapping tool that allows any user with a BCeID account to view data and do basic analysis and map mark-up. The tool offers a variety of layers of geospatial datasets, including the karst potential data. You will find the karst potential digital map layers in the Planning folder.

MapPlaceBC is a geospatial web service that provides access to maps and databases held by the B.C. Ministry of Energy, Mines and Low Carbon Innovation[BI1] . You will find geoscience information including bedrock geology data useful for karst inventories at all levels. (See B.C. Digital Geology below.)

BC Digital Geology. The British Columbia Geological Survey offers province-wide digital coverage of bedrock geology from compilation of field mapping at scales from 1:50,000 to 1:250,000. The mapping is continually updated. The current version of B.C. bedrock geology was compiled in 2019.

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Planning-level karst inventories

What are planning-level karst inventories?

Planning-level karst inventories are carried out at 1:20,000 or 1:50,000 scales to obtain an overview of karst attributes over an area of interest the size of a landscape unit or watershed. This intermediate level of karst inventory can be particularly helpful if a series of forest cutblocks and roads are anticipated over a large, well-developed karst unit.

There are two kinds of planning-level karst inventories:

• Regional-level planning karst inventories. These are undertaken to confirm whether karst occurs in areas where its presence is suspected and to assess whether further inventory work is needed
• Detailed planning-level karst inventories. These are undertaken when karst is already known to occur in an area. The main purpose is to identify, assess, and rank polygons of karst in terms of their vulnerability potential

What are the purposes/objectives of planning level karst inventories?

Information from planning-level karst inventories can be used to:

• Delineate the boundaries of a karst unit and determine the distribution and variation in karst development over a landscape
• Identify operable areas within a tree farm licence and estimate net-down areas due to karst terrain,
• Identify karst and non-karst catchment areas that may directly or indirectly impact downstream karst units
• Help direct operational-scale karst inventories by identifying significant surface karst features, sinking streams, springs, and other prominent karst features that may require further investigation at the site level. (See Karst Field Assessments below)

Planning-level inventory data are used to stratify the identified karst unit into polygons rated for karst vulnerability potential. The vulnerability potential polygons provide a preliminary indication as to the extent and intensity of karst development within a particular area.

Information from planning-level karst inventories can also be used to support landscape or watershed planning.

What triggers when planning-level karst inventories are done?

A planning-level karst inventory could be triggered if reconnaissance-level karst potential maps indicate that an area of proposed forestry activity may be underlain by karst, or when karst is known to occur in or around this area. A planning-level karst inventory could also be triggered if karst features have been identified on the ground in or near the area of the proposed activity.

How are planning-level karst inventories done?

As a first step, all available relevant information for the area of interest is collected and working maps are prepared. Existing information can range from bedrock geology maps to any previous karst inventory and assessment reports. LiDAR, which is discussed in greater detail in the section on remote sensing and karst, below, may be helpful if it is available.

Field work follows the initial office work and data compilation phase. The main field tasks include:

• Bedrock geology mapping to establish the boundaries and extent of the karst unit
• Karst mapping and vulnerability potential rating to delineate and stratify karst polygons
• Identification of significant surface karst features and hydrological features
• Determination of karst catchments and hydrology
• Identification of karst flora and fauna and associated habitats
• Identification of geomorphic hazards

Who carries out planning-level karst inventories?

Planning-level karst inventories are usually commissioned by a forest agreement holder or another forest organization. The inventory should be directed or supervised by a professional with knowledge and experience in bedrock geology, terrain mapping, and karst.

Are planning-level karst inventories available to the public?

Two planning-level karst inventories meeting provincial standards have been prepared in B.C. The inventories cover two tree farm licences and two forest licence areas on Vancouver Island. No additional conforming planning-level inventories have been completed in B.C. since 2004.

Planning-level karst inventory reports and maps are not widely distributed or made accessible to external users.

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Karst field assessments

What are karst field assessments?

Karst field assessments (KFAs) are karst inventories done at the scale of an area connected to a forest cutblock or road. They are primarily surface karst inventories carried out at 1:5,000 or 1:10,000 scales. KFA tasks can include subsurface evaluations if any caves are encountered. 

What are the objectives of KFAs?

KFAs are usually undertaken to evaluate karst attributes within a relatively small operational area of interest (for example, a proposed cutblock or in an area connected to a cutblock or road).

The results of the KFA are used to develop appropriate management strategies for the broader karst landscape and individual karst features. (See Karst Management Objectives in  Lesson 7.)

What triggers when KFAs are done?

KFAs are most often initiated when forestry activities are planned at the site level and karst, or karst features, are known or suspected to occur.

These detailed assessments are recommended prior to road construction or timber harvesting on karst terrain and should typically be carried out prior to or during the preparation of site-level plans.

A KFA can also be triggered when forestry activities are planned within non-karst drainage basins contributing water flows to known or suspected karst units downstream. In this case, the KFA would be carried out on the known or suspected karst units located downstream of the area of proposed development.

How are KFAs done?

KFAs are primarily surface karst inventories involving the collection of field data on karst terrain, individual karst features, and karst streams.

The information collected is used to:

• Stratify the karst area of interest into map units (polygons) of similar karst attributes and vulnerability
• Identify karst features where specific protective measures are recommended as best practices for forest operations

Some of the main field tasks for KFAs include:

• Assessing and stratifying the vulnerability of the karst landscape
• Identifying, mapping, and assessing the significance of karst features, including caves
• Assessing karst streams

These tasks are described in more detail in the following sections.

Assessing the vulnerability of the karst landscape

The vulnerability of the karst landscape at the KFA level is determined using a standardized procedure that evaluates three major criteria:

• Epikarst sensitivity
• Surface karst sensitivity
• Subsurface karst potential

Final vulnerability ratings for the karst landscape are determined for each karst polygon in four possible categories of low, moderate, high, or very high. The standardized procedure is described in Karst Inventory Standards and Vulnerability Assessment Procedures for British Columbia.

The final vulnerability ratings determined at the KFA level are used to guide appropriate forest management practices for the karst landscape within each polygon based on the assessed level of vulnerability.

Assessing the significance of karst features

The standard procedure for determining the significance of surface karst features, including cave entrances, involves a mainly qualitative evaluation of 10 criteria ranging from dimensional characteristics to visual quality. Detailed procedures for determining the significance of karst features are provided in Karst Inventory Standards and Vulnerability Assessment Procedures for British Columbia.

KFAs are not considered complete if any caves found under or near areas proposed for forestry activities (for example, timber harvesting, road building and maintenance, or silviculture) have not been evaluated and mapped.

Streams are assessed during the KFA to see if they sink or lose water into the subsurface. Special riparian management considerations are recommended for specified distances along sinking or losing streams, based on:

• The measured width of the stream
• The assessed significance of the karst resources receiving the water

The procedures for assessing streams and determining the significance of recipient karst features are described in Karst Inventory Standards and Vulnerability Assessment Procedures for British Columbia.

Who carries out KFAs?

Forest agreement holders commission KFAs. Contracted personnel typically carry out these karst inventories.

KFAs should be carried out by persons that have successfully completed the three-day Resources Information Standards Committee (RISC) Karst Field Assessments Training Course.

A person tasked with preparing a technically sound and rational KFA must thoroughly understand karst processes. They are also expected to:

• Have a comprehensive working knowledge and understanding of the standard karst assessment methods and procedures
• Be familiar with the principles and practices of karst management
• Be capable of recognizing and identifying different types of karst terrains and features
• Know how to evaluate karst-specific environmental, health, and safety risks
• Know how to formulate the appropriate karst management measures
• Be familiar with the karst requirements of applicable regulations, policies, protocols, and guidelines

Additional academic background or professional credentials, advanced training, and other qualifications and competencies are recommended for persons carrying out the more specialized facets of karst work.

Are KFAs available to the public?

A forest agreement holder who commissions a KFA retains the information except in cases where legislation requires annual reporting of specific karst resource feature locations. Specific data reporting may be required by regulation in parts of B.C. For example, forest agreement holders in the South Island Natural Resource District must report annually on the locations of any karst resource features in, or contiguous to, cutblocks or roads.

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Remote sensing and karst

Airborne remote sensing methods have progressed and can yield more detailed information about karst terrain than was previously available. Methods include high-resolution imaging in the visible light range to hyperspectral imaging and laser scanning.

Recent developments in compact sensor technology are making it possible to mount small sensor payloads on unmanned aerial vehicles (UAVs). Employing UAVs can be advantageous when atmospheric conditions preclude observation by orbiting satellites or overflights by manned aircraft from distant bases.

Light Detection and Ranging (LiDAR)

LiDAR is a remote sensing method that uses light in the form of a pulsed laser to measure the exact distance of an object on the earth's surface. As some of the light pulses will pass between tree branches and foliage, the method can be used for surveying certain karst features under forest canopy that are too difficult to detect using the best available topographical (contour) maps, aerial photos under stereoscopic view, or even high-resolution satellite images.

There is good correlation between karst depression features identified and modelled using LiDAR-derived data and the real features verified on the ground.

LiDAR can also be used to more accurately map contributing non-karst catchment areas at the scale needed for effective karst management downstream. Discrete mapping of these areas at the resolution required is not as feasible using ordinary topographical mapping or traditional field methods.

The relief visualization technique commonly used for karst is the shaded bare earth imagery called hillshade. However, geospatial specialists with LiDAR and karst expertise can use algorithms to extract more spatial karst information from the LiDAR point cloud data. The specialists must first determine from the meta data if LiDAR data have been corrected or otherwise adjusted (for example, “thinned”) in post processing.

LiDAR data acquired using manned aircraft can have certain inherent limitations depending on the scan angle. For example, horizontal openings in vertical or overhanging bedrock walls are less likely to be detected or differentiated with a tighter scan angle. Also, the karst potential of an area can be overrepresented if minor depressions in non-karst terrain are mistaken for karst features. False positives can also happen if non-natural ground depressions such as ballast quarries and catch basins are not properly identified and subtracted.

Currently, LiDAR datasets do not cover all of B.C. The data remain the property of the parties that pay to acquire them and are generally not shared externally except through special requests and data-sharing agreements.

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Test your knowledge