frst 557 forest operations module lecture 4a visual objectives

FRST 557

Forest Operations Module

Lecture 4a

Visual Objectives

1.0 Lesson Overview:

Workshop 2a introduced the planning “tools” of size, shape, and sequence.

This lesson will introduce the use of those tools specifically to visual planning.

2.0 Lesson Preparation:

Have access to, and be familiar with the contents of the following British Columbia

Ministry of Forests’ Forest Practices Code Guidebooks:

Landscape Unit Planning Guide (March 1999)

Visual Impact Assessment (January 2001)

3.0 Lesson Objective:

This lesson will provide you with some examples of application of seral stage to achieve

objectives in visual planning.

4.0 Visual Objectives

A visual landscape unit (VLU) or a “viewshed” is a landform that is visible from one or

more viewpoints. Landscape units that are considered to have value as a visual resource

usually require some level of a visual impact assessment (VIA) as an early part of a

planning process. A VIA will include an inventory of visual resources along with ratings

of sensitivity and the ability for the landscape to absorb or buffer any changes (Visual

Absorption Capacity – VAC) due to harvesting operations or other modifying activities

or events.

A VIA will make a statement of existing visual conditions and, using similar terms, will

state visual quality objectives (VQO) for operations planning. VQOs range from no

visible activities through significant and dominant modification. Through the entire

FRST 557 – Lecture 4a – Visual Objectives

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range of objectives, planners will consider landform shapes, harvest block size, shape,

and sequence, and the use of time between harvest passes.

Visibility is affected by:

Topography (the slope relative to line of sight)

Size and shape of harvest blocks

o Harvest blocks try to consider and imitate naturally occurring sizes and

shapes.

The type of harvest (silvicultural) system and the sequence.

o By progressing from back to front, a screen of trees reduce visibility

The height and density of trees in the foreground

Green-up of harvested areas

The following table lists five general visual objectives. For a range of VACs, possible

objective disturbance values and harvest methods are suggested.

Visual Quality

Objectives

(VQO)

Visual Absorption

Capacity

(VAC)

Example of

Maximum Visible

Disturbance

Possible Silvicultural

System

Preservation Zero Zero Single Tree Selection

Retention Very Low Very Low Selection

Partial Retention

Low 5 % Selection or “Variable

Retention” Medium 10 %

High 15 %

Modification

Low 20 %

Any Medium 25 %

High 30 %

Maximum

Modification

Not Applicable Not Applicable Any

The effect of slope is illustrated in the following series of illustrations. A disturbed area

of a constant size and shape can be quite inconspicuous if the line of sight is at an angle

(slope) similar to the ground slope of the disturbed block. Foreground trees do not need

to be of a significant height to effectively screen the disturbance.

3 m tree

15 years old

Line of Sight

Not Visible

Viewpoint


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If however, the slope of a harvested block is significantly greater than the viewing angle,

the disturbance becomes quite visible, especially if foreground trees are short.

3 m tree

15 years old

Visible

Viewpoint

For a steeper slope harvest block to be screened, taller trees are needed in the foreground.

8 m tree

35 years old

Not

Visib

le

Viewpoint

A general procedure for harvest planning in visually sensitive areas is to start at a distant

point and work toward the viewpoint, always working behind a screen of mature trees.

The sequence requires attention to the natural patterns, block sizes, and the use of

greenup in the scheduling.


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Although there is evidence of excellent regeneration of previous logging activity in the

foreground, the valley bottom, and the far ridge top, the harvest of the mid-slope of this

hillside did not consider any visual impact from the viewpoint.

Slope stability issues are also illustrated here.

This entire area is regeneration after logging.

The area in the foreground is natural regeneration 60 years in age. Note the mixture of

coniferous and deciduous species. The background is a 30-year old

Douglas fir plantation with natural seeding of other coniferous species.

The middle area is a 9 year old mixed species plantation


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Except for an access road across the top of these ski runs, note how the shape of the

cleared areas resembles the natural avalanche tracks. Both the shape and the positive

identifiable use result in an acceptance of the disturbance.

These harvest blocks so closely resemble ski runs and nearby avalanche tracks that they

were accepted in spite of being visible from a major highway.


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Size, shape, and the use of screening in the front and back of this block

mitigate the visual impact.

See Appendix 9 of the Forest Practices Code Visual Impact Assessment Guidebook

(January 2001) for additional illustrations.

5.0 Visual Planning

Read the following two sections of the Forest Practices Code Visual Impact Assessment

Guidebook (January 2001):

Appendix 7 on sight line plotting

Appendix 8 on calculating percent alteration in perspective view

Visual planning may range from a few photographs and simple projections of perspective

views to very detailed planning using digitized data.

The following illustrations are provided courtesy of Enfor Consulting Ltd.

(http://www.enfor.com) using their software “Visual Landscape Planner”

http://www.enfor.com/


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Using a development plan map, key viewpoints are selected for detailed analysis.

In this case, a point is identified in an inlet to the east of the landscape unit. This area is

located on the Sechelt Peninsula. Source: Enfor Consulting Ltd.


8

H M-H

P PR

A photo image is digitally produced to evaluate the visual impact of the proposed

harvesting. Source: Enfor Consulting Ltd.

Note the circular symbol in the upper left part of the image.

The codes indicate:

H Visual sensitivity class of high

M-H Visual absorption capacity of medium to high

P Existing visual condition of preservation

PR Visual quality objective of partial retention

Often several iterations will be made. Area shapes and sizes will be modified and put into

perspective view to test visual quality objectives. Source: Enfor Consulting Ltd.


9

Several forest companies operate in the proximity of the 2010 Winter Olympics in

Whistler, BC. These illustrations examine the possible impact of harvested blocks.

Because of the timing of the Olympics, the digital projections show winter conditions

with snow.

Note the identified viewpoints.

Source: Enfor Consulting Ltd.


10

Digital aerial projection. Source: Enfor Consulting Ltd.





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6.0 In Closing

Visual resources are often one of the key resources used for planning. If visual quality

objectives can be met by the plan, usually objectives for a number of other resources will

be achieved as well.

frst 557 forest operations module lecture 4a visual objectives

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