Soil Risk Matrix for Off-Road Vehicle Damage (Changes) to Soil:

Lake Koocanusa Area - Final version, May 28, 2010

Mike Curran, PhD, PAg, Research Soil Scientist, BC Forest Service, Nelson Introduction Several factors contribute to the potential for “Damage to the Environment: Changes to Soil” arising from off-road vehicle use on forest and range soils. These include environmental and operator/equipment factors. This document focuses on the environmental factors, but also mentions some operator/equipment factors that are likely just as, or more important. This information, along with other information and the knowledge and experience of C&E and District staff, should likely be conveyed to off-roaders in extension efforts aimed at preventing the damage from occurring. [A brochure may be the most appropriate venue to communicate the extension document, and perhaps social media such a “YouTube,” where there is apparently a number of local “mud-bogging” exploits for the below the high water line area.] The reader should be aware that mud-bogging above the high-water line would likely constitute Environmental Damage under the Forest and Range Practices Act and Regulations. NOTE: most of the surface soils in the study area are susceptible to rutting when wetter, and to loss of cohesive strength (and resulting displacement) when drier, and also to erosion of the loosened soil by both wind and water.

1. Environmental factors. The primary factors of concern are inherent site (topography and slope), soil moisture conditions at the time traffic occurs, and the inherent soil properties:

1.1 Topography:

Slope and topographic position are important. Steep, scarp-like slopes (e.g., over 50 %) are very susceptible to loss of surface soils under vehicle wheels and tracks, which can lead to displacement of fertile topsoil layers, deeper displacement of the developed soil profile and even erosion. Toe-slope and lower, receiving slopes and depressional areas are also of concern due to greater likelihood of finer textured soils and increased moisture levels (which results in lower soil bearing strength and hence, greater potential for rutting or puddling [destruction of soil structure]).

The main slope and topographic hazards can be rated as follows: Low slope / topographic hazard

- flat or gently rolling upland areas Moderate to high slope / topographic hazard

- moderately steep hummocks associated with upland soils Very High slope / topographic hazard

- terrace and river/lake scarps (e.g., over 50 % slope gradient) - sand dunes - low-lying, poorly drained depressional areas - toe-slope positions of larger hillslopes

1.2 Steep slopes

Any clearly identifiable scarps need to be delineated for monitoring (and slope classes for the polygons can be helpful as well). Soil maps include a slope class, either based on the presence of simple or complex topography. The steep, simple slopes are likely the most attractive for “hill climbs” and also need to be identified for monitoring. These would be slope classes “H” and any slopes over 50 % (as per footnote on table). These areas have been mentioned in the above listing of hazard ratings, and delineated on the map.

1.3 Soil moisture conditions at the time of operations

Any soil is subject to damage given the right conditions – soils are usually most susceptible to damage when wetter; but some sandier and gravelly soils are most susceptible when dry (due to loss of cohesive strength, which is provided by moisture in these soils). So, any soil material can distort under traffic pressure given the right amount of moisture (e.g., I have even seen wet railroad ballast move under my bicycle tires). In the Lake Koocanusa area, most all soils have a veneer of eolian material (windblown silts and fine sands that were deposited after glaciation about 10,000 years ago, along with some volcanic ash materials that were deposit since that time). Therefore, most of the surface soils in the study area are susceptible to rutting when wetter, and to loss of cohesive strength (and resulting displacement) when drier, and also to erosion of the loosened soil by both wind and water. The soil risk matrix presented below considers the potential for this damage becoming deeper into the developed soil profile; it does not indicate that the other soils are not susceptible to shallow disturbance damage – most all the soils in the area are sensitive to some degree. The hazard rating listings and the soil risk matrix consider wetter sites, but do not take seasonal soil moisture into account.

1.4 Soil risk ratings for individual “soil types”

“Soil type,” is best considered in terms of classified soils where soil mapping exists (such as in the Lake Koocanusa LUP). Soil classification considers soil parent material and soil

development, along with characteristics like soil texture, stoniness, and internal sorting of the soil profile – all of these influence the soils resistance to compaction, displacement and erosion. For compaction and puddling (destruction of soil structure), organic, clay and silt textured soils are most susceptible, with silty soils prone to deep rutting under wetter conditions. Soils low in clay (particularly sandy and gravelly soils) are generally less susceptible to compaction and rutting, but are more susceptible to displacement of the shallow, fertile topsoil layers. Low clay content soils with smaller particle sizes (e.g., silt and finer sands that have been sorted and deposited by wind or water) are very susceptible to erosion, particularly from any ruts/trails that run straight up and down the hillsides. Therefore, one main consideration for soil damage susceptibility is the soil parent material, which influences the texture deep in the soil profile. Simplified example of how soil parent materials influence susceptibility to damage: Low susceptibility to damage

- Stony, upland colluvial soils Moderate to high susceptibility to damage

- glacial till (morainal) soils - gravelly floodplain soils

Very High susceptibity to damage

- organic soils - eolian soils (e.g., sand dunes and related deposits) - glaciolacustrine soils (old glacial lakebed deposits) - silty and sandy floodplain soils - non-stony colluvial soils associated with fluvial terraces and lowland gullied

terrain

2.0 Risk Matrix Risk is a function of hazard times consequence. The consequence we are concerned about here is “Damage to the Environment: Changes to Soil” (a new circular is being prepared on this by C&E Branch with soil scientist input). The hazard is the inherent compactibility or erodibility of the soil, along with the sensitivity of the soil to displacement of fertile topsoil. The resulting risk ratings can be presented in a table, conceptually as a simple risk matrix to demonstrate the general relationship of the factors, and specifically by “soil type” to enable specific rating of individual polygons. Here is a conceptual, simple risk matrix based on the above soil and site factors: Soil Risk Table Slope and topographic hazard Parent Mtl Susceptibility

Low Moderate – High Highest

Low L L M-H Moderate - High M-H M-H H Most H H VH 2.1 Mapped soils In the Lake Koocanusa area, soils were classified and mapped at a reconnaissance survey intensity level and published at a scale of 1:100,000. This type of survey is suitable for general planning use (but not operational planning, which requires site-specific characterization of soils and their respective ecosystem conditions). Soil is a function of parent material, topography, climate and vegetation, all acting over time. Similar soils occur where the soil formation factors are similar and soil mapping identifies these areas. Soils surveyors characterize the similar soil conditions and assign geographic names for an area where the typical soil condition (parent material, topography, texture, and soil development) has been observed. In the Lake Koocanusa area, there are several soil associations that have been mapped and they can be summarized by their parent material, parent material, texture, topography and a description of other important factors. 2.2 Application of risk ratings to soil map polygons Soil maps portray the soil individuals (associations at our mapping scale) as either simple or complex map polygons. Complexes are necessary due to mapping scale or terrain complexity (e.g., rolling terrain with low lying and upland soils). Polygon labels indicate the approximate proportions of various soil associations that are considered to occur in that area. Unless the most sensitive soil association can be mapped out of a complex (e.g., the low lying soil is visible on a more detailed projection), the rating for the complex polygon should reflect the most sensitive soil type in the polygon. Based on the soil maps and my knowledge of the area and its soils, here are specific risk ratings for the soils that occur in the study area:

Code Name Parent Mtl Texture Topography/

Drainage Description Risk

Rating as Avis Fluvial gsl Floodplain /

moderate Gravelly floodplain

Moderate - High

bf Big Fish Colluvium gsil Steep slopes / rapid

Stony, calcareous

Moderate – High

cai Caithness Colluvium gsil Steep slopes / well

Stony, calcareous

Moderate – High

cn Crowsnest Fluvial sl/gsl Floodplain / moderate

Dark coloured

High

col Colin Creek

Colluvium gsil Steep / well Stony, calcareous

Moderate – High

dl (it is “ol”)

Olivia Organic “mesic” organic mtl

Depression / very poor

Partially decomposed organics

Very High

e Elko Fluvioglacial fsl/gsl Varied / well Nonstony, calcareous, shallow

High

ex Should be “e”, above

f Flagstone Fluvioglacial s Deltas and dunes / rapid

Calcareous Very High

fl Flatbow Moraine sil Varied / well Calcareous and clayey at depth

High

fs Fort Steele Fluvial gsl Floodplain / moderate

Calcareous High

fx Fishertown Fluvioglacial gsl Varied / rapid Calcareous, shallow

High

gn Glen Cairn Fluvioglacial gsl Terraces and fans / well

(Scarps likely)

High (Very High on scarps)

h Hyak Fluvioglacial fsl/gsl Varied / well Nonstony, grasslands

High

k Kinbasket Moraine sil Varied / well Calcareous, clayey at depth

High

Code Name Parent Mtl Texture Topography/

Drainage Description Risk

Rating ke Keeney Fluvioglacial fsl/gsl Terraces and

fans / well (scarps likely)

High (Very High on scarps)

ky Kayook Eolian sil/gsl Likely some dunes / well

Nonstony, calcareous

Very High

lak n/a (Lake) m Mayook Glaciolacustrine sil

(often sicl)

Gullied terraces / well

Stone-free and calcareous

Very High

md Marmalade Moraine gsil Varied / well Calcareous and shallow

Moderate – High

mr Maguire Moraine sicl Varied / moderate

Often red, green or purple soil

High

ms Malpass Moraine sil Varied / well Some clay Moderate – High

p Plumbob Moraine sil Varied / well Grassland, shallow

Moderate – High

ro Rock outcrop

Low*

rs Rosen Lake

Colluvium gsil Steep / rapid Stony, steep soils

Moderate – High

ry Ryanier Colluvium gsil Steep / rapid Stony, steep soils

Moderate – High

sa Saha Fluvioglacial fsl/gsl Varied / well Calcareous grassland soils

High

wy Wycliffe Moraine gsil(sicl) Rolling/ Well

Calcareous, shallow

Moderate – High

NOTES:

- * “Low” does not appear on map because mapped with soils that are more sensitive.

- “Moderate – High” is used as a rating to reflect the fact that many soils in the area have sensitive surface soil layer.

- Any soil map polygons with simple, steep slopes should be considered VERY HIGH as well (slope classes “H” on the map and the steep parts of the “G” classes – i.e., other slopes over 50 % gradient).

2.3 Soil map reliability How reliably a soil map predicts the actual soil on the ground depends on several factors: survey intensity level and mapping scale, mapper skill, terrain complexity, and accessibility of individual polygons are some of the main factors. While the mapping we are using was just “reconnaissance” mapping (1:100,000 and likely without checking of many of the polygons), the mapper was considered very good, the terrain is not very complex, and this area had good access at the time the field work was done. My experience with these maps is that they are very useful for general planning purposes (our use here) and they are quite accurate. There will be areas of different soils (“minor inclusions”) that exist due to mapping scale, or airphoto obscurity, or subtle differences in landforms. However, by using slope in addition to the soil map base, the resulting risk map should serve our purposes quite well.

3.0 Other factors to consider

In addition to the soil risk matrix developed above, a number of other factors will likely need to be considered in deciding where to spend limited staff time monitoring for practices that may lead to Environmental Damage: Changes to Soil. Some are discussed below, and more are no doubt already being considered by C&E: 3.1 Recently disturbed areas: Vegetation and forest floor cover help protect the surface soil from initial damage through root strength and a protective mulch cover. The soil is more susceptible to damage if the soil cover has been reduced or otherwise damaged due to previous disturbances such as fire, scarification, over-grazing, or heavy equipment disturbance (e.g., logging with high disturbance levels). Due to the predominance of grasses in the Lake Koocanusa area, this susceptibility may be short-lived, but there has been observations of soil disturbance retarding grass recovery in other areas of the Province. Therefore, recent disturbance, particularly fires, should be considered a higher priority for monitoring (or off-limits to off-road vehicle use). 3.2 Access: The heaviest traffic, and resulting damage, may be most likely to occur in areas where people congregate, either along roads/gravel pits, near recreational areas, or recreational destinations (e.g., lakes/wetland areas, as well as some hilltops/viewpoints). 3.3 Historically used areas: These are obvious areas to start looking for violations; however, with increased pressure on these areas new areas are apparently occurring. The soil risk map, combined with access information, may help predict the locations more likely to become popular?

3.4 Traction tires Apparently, once tire or track lugs are about 1 cm in tread depth, little benefit occurs from larger lugs in terms of trafficability. In fact, under some conditions the larger lugs may cut into the supporting root matt in the topsoil and create greater changes to soils and resulting damage (and loss of traction). Many off-road vehicles may have large lugs, so this factor may need to be considered by users when selecting new tires (perhaps some dealers could offer demonstrations to help sort out what provides the best traction with the least damage?). 3.5 Moderate risk areas can sustain heavy damage In practices such as harvesting, sometimes the biggest examples of soil damage occur on the less sensitive sites. This may occur because less concern may exist and/or the soil still offers adequate traction while rutting is occurring (whereas the equipment may get stuck on sensitive soils once deep rutting or puddling starts to occur). The same may happen for off-road vehicle use. Therefore, some level of monitoring is likely still required on most of the soils in the Lake Koocanusa area, at least the accessible areas. Acknowledgements I thank Andy Cagle, Spatial Information Analyst / GeoBC, BC Min. Forests and Range, Integrated Land Management Bureau, for his diligence and keen interest in creating the map; Graeme Hope, PhD, PAg, Research Soil Scientist, BCFS Kamloops for his general comments; and Steve Jablansky, Operations Manager, Rocky Mountain District for his review comments. References: Curran, M., I. Davis, and B. Mitchell. 2000. Silviculture prescription data collection field handbook: Interpretive guide for data collection, site stratification, and sensitivity evaluation for silviculture prescriptions. BCMOF Land Management Handbook No. 47. 156 pp. Includes forms FS39A and B. Lacelle, L.E.H. 1990. Biophysical resources of the East Kootenay area: Soils. Report no. 20. British Columbia Soil Survey. Wildlife Br., Habitat Inventory Section, BC Min. Environment, Victoria. 359 pp. plus maps.

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ROADSurface

pavedlooserough

Soils Sensitivity to Off-Road Vehicle UseRank , hectares

Very High, 7285.01High, 23026.41Mod - High, 20367.13

Base LayersLake Koocanusa LUPRiverStreams

Lake Koocanusa Land Use PlanSoils Sensitivity to Off-Road Vehicle Use

see Report from Mike Curran for detailed explaination of ratings.

NOTE: Most all soils in the area have a sensitive surface layer andmay be damaged by off-road vehicle traffic, particularly traffic thatoccurs off existing trails.

Soil sensitivity interpretations from report: "Soil Risk Matrix for Off-road vehicle damage (changes) to soil: Lake Koocanusa area, Final report, May 28, 2010", by Mike Curran, PhD, PAg, Research Soil Scientist, BC Forest Service, Nelson.

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