California Department of Transportation
Caltrans > Landscape Architecture Program > Visual Impact Assessment Training > Module 2 Lesson 8
 

Module 2: Visual Character
Lesson 8: Labeling The Landscape

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Lesson 8 - Labeling the Landscape

Lesson 8 is called “Labeling the Landscape.”  We are attempting to discover what constitutes the landscape.  As the heading on the interpretive sign shown in this slide, we wonder, “What Shall We Find?”

 

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Labeling the Landscape

As shown on this slide, we will be covering six main topics in this lesson.  We are going to dissect the landscape, divide it once, twice, and then subdivide it again before we put it back together.  This process of dissection is only an analytical tool—a way for us to understand the totality of the landscape.  It is rather tedious and frequently an unnecessary step for professional landscape architects who may be familiar with the concepts we are about to explore and have perhaps many years of training and practice in analyzing the landscape.  If this is you, consider this lesson a refresher course.

Let’s first examine what the FHWA refers to as general landscape types.  These are the dozen or so large biogeographical or ecological units that characterize the landscapes of the state. They can be scattered around the state in non-contiguous groups. These landscape types will be subdivided into landscape units.  A landscape unit is simply a contiguous example of a landscape type.   In turn, individual landscape units will be merged or further divided, using the concept of viewsheds into visual assessment units.  It is the visual assessment unit that we are ultimately concerned with defining.  Each visual assessment unit has its own set of key views which are places from which an observer has a view of the landscape—either a representative view or a view of a unique visual resource. Many times unique resources can be classified, using terms established by CEQA legislation, as scenic resources. 

The slides in this lesson explain these concepts in greater detail. 

 

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Landscape Types

The landscape of California can easily be divided by different types of ecological communities.  The basis for these differences is a related set of biogeophysical attributes arising from differences in geology, hydrology, morphology, climate, soils, vegetation, animal populations, and human land-use to name some of the primary contributing factors.  

If a common name and description of these large general landscape types, are already known by the author of the VIA, they should be identified and described in the VIA document. If the name and description are not known, or if a more descriptive title is desired, the FHWA has provided a method for defining and naming these large, general divisions of the landscape as described in the next few slides.

 

Slide 51

Landscape Types

California has many landscape types.  A road may actually transect more than one type.  A landscape type is composed of a landform and a land cover. 

Landform describes the shape of the landscape, or more scientifically, the landscape’s morphology.

Land cover describes what overlays the landform, or more scientifically, the landscape’s ecology.

 

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Landscape Types

Landscape Type, as defined by FHWA, is simply the merging of Landform and Land Cover.

 

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Landscape Types

The native landscape of California has a rich variety of landforms.  These are only six examples.  Other landforms or other more commonly used terms for even these landforms shown in this slide, are permissible.  In fact, using terms that are used locally in the project area, is the ideal way to communicate with those people who will be affected by the proposed project.  

 

Slide 54

Landscape Types

Native land covers offer a similar wide-range of attributes associated with the diversity of ecological communities found in California.

 

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Landscape Types

Land cover is not only native, however, it can be defined also by human land uses—adding even more complexity to the description of landscape type.

 

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Landscape Types

The naming of a landscape type is straightforward.  The FHWA simply adds the name of the landform to the name of the land cover.  For example, the landscape type depicted in this image could be a coastal redwood forest.  The landform is coastal, the land cover is a redwood forest.

Landscape types are distributed regionally but usually not contiguously.  Although they occur in multiple locations, they tend to be visually homogeneous—that is if you’ve seen one redwood forest, you’d probably recognize another.

The boundaries of where one landscape type ends and another begins are usually fuzzy, at best.  Unless there is an abrupt landform change, there are typically transitional ecological zones between pure landscape types. 

Recognize that the name of a landscape type is the name of a large category.  Typically it is not a name of a particular place, rather it is a conceptual name applied to the landscape used to understand the context in which the proposed project will be constructed.  

 

Slide 57

Landscape Types

As a way of understanding this concept, let’s create a set of maps. Using the 11 x 17 or 8½ x 11 paper, print out a copy of the Team Project Map.  Overlay a sheet of trace paper on the Team Project Map. You will be creating three overlaying maps.  The first will delineate the study area first by landforms.  The second will record land covers.  Finally, the third will merge the first two maps into a third map of landscape types.  More explicit directions are given on the next slide.   

 

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Landscape Types

Follow the directions on the slide.  Be sure to register each map with tic marks in the corners. This will be important since all subsequent maps are built on previous maps and aligning them correctly is critical.  If possible, it is recommended that you use the marker colors as suggested in these notes.  By doing so, you will be able to build on previous maps with less confusion.  It will also allow you to follow the directions and comments in these notes more readily.

For the first map use a black marker to delineate landforms.  Label your map, “Landforms”.

Now remove the first map and lay a new sheet trace over the base map.   On the second sheet, use a green marker to delineate land cover.  Label that map, “Land Covers”.

Now place both of the maps you’ve created over the base map, aligning the tic marks.   Add another sheet of trace paper on top of this pile of maps. On this new sheet of trace use a blue marker to create a third map which merges the first two maps you’ve created to delineate landscape types. Label that map, “Landscape Types”.

You now have a map of the landscape types that exist in your project area.  This will be useful information for determining visual assessment units later in the FHWA process.  But first, let’s examine what the FHWA calls landscape units.

 

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Landscape Units

A landscape unit is a subdivision of landscape type. We will discuss how landscape units are defined and named more thoroughly in the next few slides.

 

Slide 60

Landscape Units

A landscape unit is the discreet, contiguous unit of a particular landscape type.  It typically has distinct boundaries.  It is frequently identified as a distinct place by the local population, which usually has given it a name.

 

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Landscape Units

The name usually implies a particular landscape type, at least in the local mind, for a landscape unit consists, usually, of only one landscape type.  Using the previous example of a landscape type being a coastal redwood forest, a landscape unit would be Muir Woods, north of San Francisco.  Names of landscape units frequently are proper names.

 

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Landscape Units

On a new overlay of trace paper, merge or further dissect landscape types into landscape units, as necessary. (It may not be necessary!) Remember that the more you subdivide the landscape the more complex your visual assessment will need to be.  Frequently, it is wiser to merge landscape units if they have similar landscape features. 

For example, there are arguably only four land forms shown on the base map—mountains, coastal plane, coast, and river valley.  Each of these may be divided into different landscape units, if desired.  For example, the Big and Little Purple Mountains and Purple Canyon could all be three distinct landscape units or they could be considered one large Purple Mountains landscape unit, depending on what you believe will be important to analyze in the future.  It’s a guess for now, but you can always merge or re-divide later if it becomes apparent as you move through the VIA process that your educated guess was more cumbersome than needed for a good assessment.  If you suspect that there is going to be no difference in your analysis between Big Purple Mountain, Little Purple Mountain, and Purple Canyon, merge them into a single landscape unit. 

On the other hand, if you think that there is a distinction to be made between the City of Oceanview and the Town of Golden, even though they may share the same landscape type--Urbanized Coastal Plain—go ahead and differentiate them by assigning them distinct visual assessment units, the Oceanview Landscape Unit and the Golden Landscape Unit.

As you generate your map be sure to name the landscape units.  Notice that frequently they have already been given a name by the local population.  To reduce confusion for those reviewing your VIA, try to use local names as much as possible.

 

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Landscape Units

To generate your landscape units map follow the directions on this slide.  Remember you can merge or subdivide landscape types as you create your landscape units.  Label your map, “Landscape Units”.

 

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Viewsheds

A classic way of dividing up the landscape to assess visual impacts is the use of viewsheds. Conceptually, viewsheds are similar to watersheds.  Like watersheds, topographic ridges can be used to define the limits of a particular viewshed.   There are three types of viewsheds—static, corridor, and restricted.  Let’s look at each one separately.

 

Slide 65

Viewsheds

A traditional viewshed is static and is defined as what can be seen in 360º from a single view point. What a person can see from a single spot is limited by objects—such as hills, trees, buildings—that obscure what they can see.  Nonetheless, it is only topography that is traditionally considered the only obstacle that is limiting the view.  Essentially the viewshed is defined as if the earth had a lunar landscape and, therefore, only landform mattered.  Of course we have already seen that land cover matters as much as landform in generating a landscape type and this is also true about viewsheds.  Nonetheless, since land cover is more easily manipulated than landform, land cover is considered non-permanent and thus is typically not considered when defining traditional static viewsheds.

 

Slide 66

Viewsheds

Establishing a viewshed along a corridor is more complicated.   To simplify this concept consider the experience of the driver traveling through a hilly countryside.  As the driver, rides up and over hills and into the next valley, the landscape is being presented as a continuously unfolding series of viewsheds.  As the driver approaches the crest of a hill the viewshed gets more and more constrained, until at the crest, a new viewshed of the valley below is revealed.  The crest (or ridgeline) separates viewsheds. 
Notice that for a traveler on a highway, viewsheds are directional.  The viewshed for a traveler moving in one direction can be quite different than a traveler moving in the opposite direction on the same highway.  Notice also that the viewshed for a driver is more constrained by direction than it is for a passenger who has more discretion to look to the side or even backward. 

 

Slide 67

Viewsheds

For constructing a visual impact assessment it is important to recognize the existing landscape and the potential landscape.  Trees may block views of the proposed highway for adjacent residential neighbors now, but how likely are they to remain for the life of the roadway?  Those trees may become so important that the VIA identifies that they must be retained as part of the project mitigation.

 

Slide 68

Viewsheds

Besides the standard permanent (or at least solid) obstacles that obscure views, a viewshed can be limited by atmospheric conditions—smoke, dust, fog, or precipitation can reduce the size and alter the shape of a viewshed, at least temporary.  Indeed, given obstacles and atmosphere, we can typically see only a few miles ahead even on a clear day.   It is important for an author of a VIA to recognize these limitations especially if the obstacles are episodic, like dust, fog, or precipitation that happen predictably either daily, weekly, or seasonally.

 

Slide 69

Viewsheds

Follow the directions on this slide and the next to generate a map on another sheet of trace paper of the viewsheds found in the project area.  You may need to review the Team Project Narrative to fully understand the terrain.  For example, recall that the narrative suggests that there is a crest along Purple Canyon Road between Oceanview and Golden.

 

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Viewsheds

Follow the directions on this slide to make a map of viewsheds.   Label your map, “Viewsheds”.

 

Slide 71

Visual Assessment Units

Finally, this is what we need to analyze visual impacts—a set of Visual Assessment Units.  Let’s first discuss how to create these units; then let’s define their use.

 

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Visual Assessment Units

Visual Assessment Units are easily created—they are essentially landscape units divided (or occasionally merged) by viewsheds into a series of “outdoor rooms.”

 

Slide 73

Visual Assessment Units

A visual assessment unit can also be considered a viewshed divided by landscape units.  Either way—a landscape unit divided or merged by viewsheds or a viewshed divided by landscape units—it is that portion of the landscape that has a similar landscape character that can be seen at the same time by a single viewer.  Again, an “outdoor room” is a good way to conceptualize the definition of a visual assessment unit.

 

Slide 74

Visual Assessment Units

Get another sheet of trace paper ready to make a map.  This time we will make a map of Visual Assessment Units. 

Decide which alternative or alternatives you want to use for the remainder of this on-line course.  Picking Alternative 1 will give you the opportunity to see how a VIA is developed when there is little change to the existing landscape.  Picking Alternative 4 will allow you to explore how to develop a VIA when a new road is being placed where there currently is no road.  Alternatives 2 and 3 have moderate degrees of change to both native and cultural environments.  Read the narratives again to determine which alternative would be best at assisting you in learning what you need to know to do your job well. 

Or try your hand (and head) doing all four alternatives—after all if this was a real VIA you would need to do all four anyway!  Regardless of how many alternatives you decide to work on, the directions for worksheets will assume that you are working on only one alternative, if you are working on more, simply print out another worksheet for each alternative you are studying.

 

Slide 75

Visual Assessment Units

Follow the directions on this slide to create Visual Assessment Units.  Be sure to label your map, “Visual Assessment Units.”  You will be using this map repeatedly for the rest of the course.

 

Slide 76

Key Views

Determining a set of key views for each visual assessment unit is a necessary step in the VIA process and will be essential in determining the character and quality of visual resources and any visual impacts that may be caused by highway improvements.

 

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Key Views

Selecting sites for key views requires professional judgment.  Key views need to be placed where they will provide the best information on impacts—this may be the area that the affected population considers the view most sensitive to change or it may be the view that is the most representative of the landscape. Regardless of the reason, make a note of why it is being chosen.

There are several methods for determining key views.  Sometimes it is a view taken at regular intervals—every 1,000 feet or every mile—depending on the scale of the project, the variety of the landscape, and other factors.  Sometimes to avoid the appearance of partiality, a set of random views are picked.  One of the most typical methods, however, is to pick either sites that viewers would select as being sensitive or views that are typical.

One key view for each visual assessment unit is necessary for an accurate analysis with two actually being preferred, one a view from the road, the other, a view to the road.

 

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Key Views

Add to your map of Visual Assessment Units, the locations of Key Views.  Pick at least one Key View per Visual Assessment Unit.

 

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Scenic Resources

Review the text of your Team Project Narrative and then the wording in Chapter 27 of the SER on CEQA and scenic resources, as paraphrased in this slide.  What scenic resources as defined by CEQA may be impacted by the proposed highway project?

 

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Scenic Resources

Follow the directions on this slide, adding to your map of Visual Assessment Units, the locations of Scenic Resources as defined by CEQA. 

 

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Module 2, Part A Review

You have completed Part A of Module 2. Before continuing, you may want to review this last session if you still have any questions about the concept of Visual Assessment Units or Key Views and how they are created.  Understanding them fully will be critical in subsequent modules. 

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Module 2B, Lesson 9 - Visual Character