Soil Conservation Surveys Guidebook

Table of contents

5 Survey methods for access structures

A road traverse survey or landing survey should be conducted if road widths or landing sizes appear larger than normally required for similar operations and if they are not consistent with road layout and design standards. If structures not identified in an approved plan already exist, they should be treated as an operational plan violation.

5.1 Road traverse survey

Application

Figure 2 shows layout details of the road traverse survey.

Use the following method for measuring the length and width of haul roads and permanent skid trails (i.e., excavated, bladed, or unbladed structures that will be kept free of trees to facilitate repeated stand entries).

Layout

Figure 2. Layout for road traverse survey. Measure the width at approximately 10 locations.

5.1.1 Width measurement interval

The target number of width measurements is 10. Figure 3 shows a typical cutblock, with 10 width measurements for a main haul road and 10 for a spur road.

Determine the width measurement interval by estimating the total length of road, excluding landings, and dividing by 10.

Figure 3. Separate surveys for roads with different widths. Do separate surveys, with approximately 10 width measurements, for roads that differ by more than 3 m in average width.

5.1.2 Width measurement

On sloping ground, the width measured depends on whether the fill slopes are considered favourable or unfavourable for growing trees (see Figure 4) and whether the fill slope will be kept free of trees. Surveyors should review the prescription to determine whether this information has been provided. In most cases information on fill slope material is not specified, and it it will be up to surveyors to assess whether material is favourable or unfavourable, in the field. Surveyors should consult with silviculture staff before making this assessment, especially if they are not familiar with local conditions. Detailed descriptions of unfavourable growing media are provided in the Soil Conservation Guidebook, and further information may be contained in local or regional guidelines.

Figure 4. Measuring road widths on sloping ground. Include unfavourable fills greater than 20 cm deep as part of the access structure. For favourable fills, measure only the excavated portion and the compacted running surface.

If fill slopes are unfavourable for tree growth, measure the width to the top of the cut from a point where the sidecast is consistently greater than 20 cm deep. Do not count as sidecast any accumulations of slash that are clean woody debris (i.e., containing less than 30% mineral soil). Ignore isolated patches of sidecast deeper than 20 cm that are not a contiguous part of the road fill. Road fill with buried stumps or slash is always considered unfavourable.
If fill slopes are favourable for tree growth, measure the width of the road or trail from the top of the cut to the outside edge of the running surface. Do not include the uncompacted berm and fill slope.

Road edges that will be kept free of trees (to provide adequate visibility, ensure safety standards or facilitate snow removal) should be included as part of the road area.

On level ground, measure the width in horizontal distance (see Figure 5), including:
  • the running surface plus any ditches to the outside edge of each ditch line;
  • berms that are made of unfavourable soil material that are greater than 20 cm deep; and
  • the area to be kept free of trees for visibility, snow removal, etc.

Figure 5. Measuring road widths on level ground. Measure to the outside of the ditches (if present). Otherwise, include berms of unfavourable fill if they are greater than 20 cm deep.

Record the measurements on the Traverse Survey Field Card (FS 880; see Appendix 6), and then use the Traverse Survey Calculation Card (FS 881; see Appendix 6) to do the calculations:
  1. Complete separate calculations for each type of structure, such as spur roads, main roads, and permanent skid trails. Record the measurements for each type of structure on the front or back of the FS 880 card.
  2. For each type of structure, calculate the total length in horizontal distance.
  3. For each type of haul road, measure the length of road that passes through landings and record this under comments on the FS 880 card.
  4. For each type of structure, calculate the mean and standard deviation for width from the data on the FS 880 card.
  5. For each type of structure, enter on the FS 881 card the number of width measurements, its length3 and mean width, and the standard deviation of width. If you need an estimate of landing area minus its road area, enter the road length on landings in a separate column so that the area of roads on landings can be calculated.
  6. Follow the calculation procedure on the bottom of the FS 881 card to determine the area disturbed and its lower confidence limit. When calculating the percentage of area occupied by roads and other permanent access structures, use the total (gross) cutblock area after harvesting has been completed, taking into account any deletions or additions.
  7. Use the percentage area error calculated on the FS 881 card (and on the Landing Area Calculation Card FS 886, described below) to calculate the lower confidence limit for the proportion of the cutblock occupied by permanent access structures. Follow the calculation procedures on the bottom of the Soil Disturbance Summary Card (FS 889, see Appendix 6).
 

5.2 Landing survey

Avoid surveying landings before disposal of the debris pile. If a survey must be conducted before routine debris disposal, and the edge of the constructed landing cannot be readily determined, measure to the outer edge of the debris pile.
Piles that have been burned, with ash remaining, must be assessed according to the soil conditions under the ash pile. If the pile was burned on the landing running surface or unfavourable sidecast, count it as part of the landing. Otherwise, count the burned portion as part of the NAR.

Measure landing areas depending on whether fill slopes are considered favourable or unfavourable for tree growth (the same as for haul roads):

  • If fill slopes are unfavourable, measure to the top of the cut from the point where the sidecast is consistently greater than 20 cm deep.
  • If fill slopes are favourable, measure from the top of the cut to the outside edge of the landing surface.
On level ground, include the compacted running surface, berms of unfavourable soil deeper than 20 cm, and associated ditches.
Measure landings using a hip chain traverse of the perimeter (the preferred method) or the representative length and width measurements, as described below.

5.2.1 Hip chain traverse

Complete a hip chain traverse to obtain a closure error of 10% or less. For most landings, four to eight stations will provide sufficient accuracy.

If landings are measured using a closed traverse, record the net landing areas directly on the FS 886 form.

5.2.2 Representative length and width measurements

Hip chain representative width and length measurements. Estimate one-quarter and three-quarters of the total distance on the centreline of each dimension (see Figure 6), and record the information on the Landing Area Calculation Card (FS 886; see Appendix 6).

Follow the calculation procedures on the Landing Area Calculation Card (FS 886). To calculate landing area without the area of roads that cross landings, follow these steps:

  1. Determine the length of roads on landings from the road traverse.
  2. Determine the area of roads on landings:
    area of roads on landings = length of roads on landings x average road width from the FS 881 card
  3. Subtract the area of roads on landings from the total landing area before calculating the lower confidence limit for landings.
  4. Use the percentage area errors from the FS 886 card for landings and the FS 881 card for roads to calculate the lower confidence limit for the proportion of the cutblock occupied by permanent access structures. Follow the calculation procedures on the bottom of the FS 889 summary card.
To be in compliance, the lower confidence limit for the proportion of the cutblock occupied by all permanent access structures must be less than the maximum allowable limit specified in the prescription.


Figure 6. Idealized layouts for landing surveys. It can be (a) a rectangular landing, (b) an elliptical landing, or (c) a complex landing shape. Measurements are taken at points that approximate one-quarter and three-quarters of the length and width of each landing.


3 Use the total length if, when you are calculating the landing area, you exclude the area of the roads that cross through it. Otherwise, subtract the length of road on landings from the total length, but include the areas of road that pass through landings in the landing area measurement.

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