California Department of Transportation

Module 3: Visual Quality and Visual Impacts
Lesson 13: Assessing Visual Impacts

Slide 46

Assessing Visual Impacts

You have now have completed the narrative and numerical assessment of the visual quality of both the existing and proposed scenes.  We are now ready to begin assessing the visual impacts by assessing the differences between the “before” images and the “after” images.

Let’s move on to Lesson 13 to gain an understanding on how to assess visual impacts. 


Slide 47

Assessing Visual Impacts

As part of this lesson we will first finish the analysis of visual impacts for our team project by describing and rating the changes one alternative will cause to the visual quality of the visual assessment unit you have chosen to assess.  Next we will learn how to combine the measurements for changes in visual character with the measurement of changes to visual quality to get resource change.  Next we will show how resource change when combined with viewer response will yield visual impacts

We will then see how to adjust our findings for cumulative impacts. 

We will conclude the lesson by applying these concepts to our Team Project.


Slide 48

Changes to Visual Quality

We are now going to determine change to visual quality at your chosen key view.


Slide 49

Changes to Visual Quality

Continuing with the Part 5 worksheet, calculate and record in the “Change” column the numerical difference between the “before” and “after” numerical ratings.  Also describe what changed about vividness, intactness, and unity.

When you have completed filling in all the boxes in the rows labeled vividness, intactness, and unity, go to the bottom of each column to calculate and record the “Total” of the numeric ratings.  Divide the total by 3 and record the average rating for Visual Quality.   

The box in the bottom row, far right column is for recording the value of the change in visual quality.  Transfer this number to the FHWA VIA Process - Concept Diagram shown on the next slide.


Slide 50

Changes to Visual Quality

Using the FHWA VIA Process - Concept Diagram Worksheet you have already begun to fill in, add your answer for the change to visual quality in the upper right blue box.


Slide 51

Calculating Resource Change

Continuing on the FHWA VIA Process - Concept Diagram Worksheet,  calculate and record in the appropriate box, the “Resource Change” by adding together the value of  the “Change to Visual Character” and the value of the “Change to Visual Quality.”  This completes the set of blue boxes.


Slide 52

Calculating Visual Impacts

Now add the absolute value of the resource change (forgetting momentarily if the number is positive or negative) and add it (as a positive number) to the value of the viewer response.  Divide that number by two, to get the amount of visual impact.  Assign a positive or negative value to the amount of visual impacts by transferring the positive or negative sign for resource change to this number.

Following the same steps, generate a descriptive narrative for the visual impact.
You have now completed an assessment of visual impacts for one key view in one visual assessment unit.  Once you complete the assessments for all of the key views for all of the visual assessment units in the project, you can begin to write the VIA.


Slide 53

Calculating Visual Impacts

Here is an example of how one Caltrans project recorded its numerical information for one visual assessment unit.  It also had a complementary descriptive narrative.

These pages can be found in the I-5 VIA Ratings Example.  These examples are pages 116 and 117 in the complete I-5 VIA which is in the I-5 VIA Example Report.


Slide 54

Adjusting for Cumulative Impacts

Caltrans assesses whether a project has cumulative impacts.  Cumulative impacts are those that result from past, present, and reasonably foreseeable future actions, combined with the potential impacts of the project.  This is a complicated area.  Caltrans has separate training on cumulative impacts.  The Landscape Architect should work closely with the project’s Environmental Generalist to ascertain if there are cumulative impacts and how they should be incorporated into the VIA.


Slide 55

Adjusting for Cumulative Impacts

The author of the VIA has had some exposure to the concept of cumulative impacts when they answered the SER Questionnaire.  Be sure to review your answers and your thinking when you answered this question originally.


Module 3B, Lesson 14 - Mitigation