Viewshed Protection Model Ordinance Survey


Viewshed Analysis and Report: Work Plan Item 10-19

The February 15, 2005 referral from Supervisors Beall and Alvarado included a request
that Planning Office staff review the ridgeline/viewshed protection ordinances of cities
within Santa Clara County. Staff expanded its research of different jurisdictions’
approaches to viewshed preservation in response to this request.

Staff evaluated the relevant policies and ordinances of each city within Santa Clara
County that has hillside development policies and found that their value as models
varies considerably. While staff found useful elements in the regulations of several
local cities, the Town ofLos Gatos Hillsides Standards and Guidelines document has

been especially valuable, as it is a very comprehensive, relevant and up-to-date set of
viewshed-protection standards and guidelines.

In addition to local ordinances, staff looked to various other cities and counties in
California and elsewhere that might provide useful examples of viewshed-protection

Staff reviewed the regulations of the following jurisdictions for this survey:
Within Santa Clara County:



San Jose

Los Altos Hills

Morgan Hill


Napa County
Santa Barbara County

Telluride (Colorado)

Santa Cruz County

Walnut Creek

San Rafael


Los Gatos


Clark County (Nevada)
Los Angeles (city)
Los Angeles County

The following pages summarize some of the better viewshed-protection strategies
gleaned from these jurisdictions. They cover a range of topics that could each be a
component of a comprehensive approach to effective viewshed protection in Santa
Clara County.


The following jurisdictions utilize tiered regulatory structures where level of review is
based on scale and other visual-impact criteria. This system has the advantage of being
efficient, in that it focuses energy on the larger, potentially problematic houses. It also
actively encourages applicants to build smaller, less visible houses.

San Rafael: The Hillside Development Overlay District(-H)applies to all lots in the
hillside resource residential and hillside residential zoning districts. The regulations

for the Hillside Development Overlay District also apply to all lots with an average

slope greater than twenty-five percent(25%). All applications are also evaluated

for confon-nity with the Hillside Residential Design Guidelines Manual.

Applications must include comprehensive “Compliance Checklist” which addresses

all applicable design standards and criteria.

Regulatory structure is two-tiered. Applications meeting basic criteria are reviewed
administratively by staff, while applications exceeding threshold criteria are subject
to review by the City Council, upon the recommendation of the Design Review
Board and the Planning Commission. Applicant must demonstrate that alternative
design concepts carry out the objectives of the ordinance section and are consistent
with the general plan. San Rafael Municipal Code, Chapter 14.12: Hillside
Development Overlay District (-H).

Napa County: Projects on parcels in the Viewshed Protection Combination District
(-V) are subject to specific viewshed-protection findings in addition to the findings
required for use permit approval. Site development on parcels outside of the -V

combination district may be subject to the requirements of the Viewshed Protection

Program. This ordinance applies to all applications for new, expanded or

remodeled structures located on slopes of fifteen percent or more or located on a
minor or

major ridgeline, and projects involving significant grading or earthmoving

activity on slopes of fifteen percent or more.

The Viewshed Protection Program provides a three-tiered application review

structure. Projects meeting baseline standards are subject to administrative (staff
level) approval. Projects exceeding administrative review thresholds are subject to
discretionary review by the either the Zoning Administrator or Planning
Commission, as detenuined by planning director. Specific findings must be made
for the Zoning Administrator or Planning Commission to approve the project.


Prior to issuance of a building permit, the property owners must execute and record
a deed restriction requiring building exteriors, existing and proposed vegetation, to
be maintained by the owner or the owner’s successors so as to prevent the project
from being viewed from any designated public road. Napa County Zoning
Ordinance, Chapter 18.106: Viewshed Protection Program.

All else being equal, smaller houses will have lesser visual impacts than larger houses.
Absolute size limits are employed by several jurisdictions, and currently apply to the
Los Altos area (ni) and Milpital foothills (d2). Based on the 1996 experience of the

West Valley Hillsides Study where house size limitations were proposed (and roundly
rejected), this may not be as practical and politically viable as a house size threshold
system as is utilized by Napa County.
Los Gatos: The maximum floor area of each house is detenuined by using a floor area

ratio adjusted to slope. The maximum gross floor area is 6,000 square feet for lots
containing a net lot area of more than 32,000 square feet unless the Planning
Commission grants an exception based on nine conditions. Cellars, garages up to
400 square feet in area, stables that are not fully enclosed and barns that do not
exceed the maximum floor area allowed for accessory structures based on gross

parcel size are not included in the gross floor area calculation. Los Gatos Hillside

Development Standards and Guidelines.

San Rafael: For all zoning districts with which a hillside development overlay district
is combined, the maximum gross building square footage of all structures

(including garages and accessory structures over 120 square feet) is limited to 2,500
square feet plus 10% of the lot area with the maximum gross square footage set at
6,500 square feet. San Rafael Hillside Residential Design Guidelines.

Napa County: The ordinance allows administrative level review if maximum floor

area of the main residence or agricultural structure is 4,000 square feet or less and
the maximum cumulative floor area for accessory strucmres is 2,500 square feet or

less. Projects exceeding this threshold are subject to discretionary review by
Zoning Administrator, or upon referral. Planning Commission. Napa County
Zoning Ordinance, Chapter 18.106: Viewshed Protection Program.


Woodside: Maximum house size is 6,000 square feet in RR (Rural Residential) and

SCP (Special Conservation) districts. An exception, to 8,000 sq ft max, may be
made by the Planning Commission on lots that are 150% or larger than the

applicable minimum lot size for the zoning district. Additional findings relating to
viewshed impacts must also be made. Town of Woodside Zoning Ordinance,
Chapter 153.047: Building Limitations.


Ridgeline protection has been deemed a priority of the County by the General Plan, but
has also been challenging to implement largely due to difficulties in defining the land

area that constitutes a ridgeline. Topography is complex, and what would appear as a

ridgeline from a close-up vantage point may not from farther away. Defining and
mapping the protected ridgelines will be the most important challenge for successfully
implementing ridgeline protection policies.

Los Gatos: No primal^ or accessory building may be constructed so as to project
above the physical ridgeline as seen from any “viewing platform”(There are four

specific locations on the valley floor deemed “viewing platforms,” and the
reviewing authority may designate one or more other locations as viewing

platforms for a given application). If it is determined that a building cannot feasibly

be sited below a significant ridgeline, the maximum building height shall be

reduced to 18 feet. Los Gatos Hillside Development Standards and Guidelines.

San Rafael: Development of new structures within 100 vertical feet of a visually

significant ridgeline (designated by official map)is prohibited unless this restriction
precludes all reasonable economic use of the property. An exception may be
granted if the decision-making body makes specific findings. San Rafael Hillside
Residential Design Guidelines.

Napa County: One of the required findings for certifying that a project application

be reviewed at the administrative level is that the highest point of the proposed
structure is located more than twenty-five vertical feet below a major or minor

ridgeline. Napa County Zoning Ordinance, Chapter 18.106: Viewshed Protection


Los Angeles County: The highest point of a building (excepting chimneys, antennas
etc) must be at least 50 vertical feet below a significant ridgeline (designated by

official map). A variance is required for any exception to this policy. Variance
findings would include standard variance findings plus additional findings of
maintaining visual integrity of ridgeline, and mitigating any adverse impacts on
viewshed. Los Angeles County Code, Title 22: Planning and Zoning.


This important component of viewshed protection is challenging in that can be more is
subjective than more quantitative criteria. Nonetheless, a well designed, proportioned
house can blend in well into its backdrop regardless of size.

Los Gatos: The maximum allowed height for homes in hillside areas is 25 feet. In

addition, the maximum vertical differential between the lowest elevation along the

building’s perimeter to the highest part of the building is 35 feet. Buildings that

extend above a ridgeline or that are visible from a viewing platform have a

height from the lowest to highest points of 28 feet. Ridgeline and visible

homes cannot extend more than 18 feet above the existing grade. Elevations that

appear as three stories from downslope vantage points are prohibited.
Qualitative standards and guidelines encourage simpler building forms and

avoiding architectural styles that are “inherently viewed as massive and bulky.”
Building foundations and roofs should step with the natural slope, and buildings

should be set into excavated slope. A thoughtful balance of horizontal and vertical

components should be used to reduce apparent bulk, and to avoid massive two-story
wall planes on the downslope face. Modest overhangs, projections, alcoves, plane
offsets, and varying elevations (such as stepping back second stories) are

-aged as they create light and shadow, providing more favorable textural
makeup against the natural backdrop. Story poles are required for evaluation of
visibility. Los Gatos Hillside Development Standards and Guidelines.


Napa County: One of the required findings for certifying that a project may be

reviewed at the administrative level is that the height of the structure is twenty-four

feet (24’) or less as measured from finished grade along fifty percent or more of the
longest wall as viewed from any designated public road. In addition, roof angles
and composition must be designed to conform to existing landforms and landscape
to also qualify for review as an administrative project. Napa County Zoning
Ordinance, Chapter 18.106: Viewshed Protection Program.


Telluride, CO: Encourages setting buildings into slope to reduce perceived mass and
scale. Buildings should step down with slope to reduce apparent height and to
avoid monolithic downslope wall. Encourages simpler building forms similar to
historic buildings in town (modest rectangular forms with rectangular additions
with steep gable and shed roofs). Story poles required for evaluation of visibility.

Town of Telluride Transitional Hillside Treatment Area and Transitional Hillside


Hillside development often involves significant grading and the grading for driveways,
house pads and yards can often be the most visible component of a development.

Los Gatos: Standards emphasize minimal grading and avoiding the need for retaining
walls. Favor cutting versus filling to set structures into hillsides and avoid larger
cuts and retaining walls in front of houses where most visible. Prescribe varied,
non-uniform slopes for a more natural (less “engineered”) appearance. Standards
for grading quantities are specified for each site element(house, accessory building,
pool, tennis/sport court, driveway, other). Has maximum allowed depths of cuts
and fills in hillsides. No stated provision for exception to these standards. Los
Gatos Hillside Development Standards and Guidelines.

San Rafael: Standards emphasize minimal grading and designing final grade to have

“natural appearance” on slopes between 5:1 and 2:1. Favor cutting versus filling to
set structures into hillsides and avoid larger cuts and retaining walls in front of
houses where most visible. Minimize height of visible retaining walls and require
natural stone or earth colored materials. Graded pads shall be of a minimum size

for structures and open space (Pads for tennis courts and swimming pools are
discouraged). San Rafael Hillside Residential Design Guidelines.

Large visible retaining walls can double or triple the visibility factor of a hillside house.
Along roads and driveways they can scar the landscape and destroy the natural
appearance of the hillside.


City of Los Angeles: Limits height of individual retaining walls to 12 feet, or a series
of two 10-foot(max) walls offset by at least three horizontal feet. Any walls taller
than eight feet must be designed to be completely screened by landscaping.
Discretionary exceptions possible with zoning administrator approval, and subject
to visual-impact findings. Statutory exceptions include public agency projects,

prior approved retaining walls and emergency repair of an imminently unsafe
condition. Los Angeles Municipal Code Subsection 12.21C8: Retaining Walls in
Hillside Areas

Clark County, NV: Limits height of individual retaining walls to nine feet and allows
a series of up to four nine-foot walls for a combined 36 vertical feet. A six-foot
minimum horizontal staggering of consecutive walls is required. Visible walls must
incorporate native stone materials or otherwise be of low-contrasting earth-tone
colors. Clark County Municipal Code Section 30.64: Site Landscape and Screening


Practical factors conspire to prevent landscaping from being a perfect solution to visual
impact mitigation (especially on steep hillsides), but a well-designed landscape plan
can provide some visual screening, create a more ^established” look, and also frame

views from the house in an aesthetically pleasing way. The County does not currently

have a landscape ordinance.

Santa Cruz County: Has veiy comprehensive landscape ordinance that would appear
well adapted to Santa Clara County’s hillsides. Encourages use of native or
naturalized species and requires certain invasive special be removed. Landscape
maintenance and irrigation requirements are very clear and practical. Santa Cruz
County Code Section 13.11.075.

Woodside: Has comprehensive list of trees and shrubs suitable for woodlands and
hillside areas, and identifies fire-resistant species among that list. Town of
Woodside Residential Design Guidelines.

Los Gatos: Vegetation restoration required for all cuts and fills. “Defensible space
criteria for designing landscaping to provide fuel break for fire protection. 30-foot
perimeter zone(Zone 1) immediately around hose has well-watered and fire
retardant foundation plantings. Secondary perimeter(Zone 2) 30-70 feet, low

plants, no trees. Tertiary perimeter(Zone 3) up to 100-200 feet of trimmed trees
such that canopies are discontinuous. All landscape plans are reviewed by the Fire

Department. Los Gatos Hillside Development Standards and Guidelines.

Telluride, CO: Specifies landscape plans must be “rough, natural and/or subdued in
character.” Discourages use of exotic plants and sod. Town of Telluride
Transitional Hillside Treatment Area and Transitional Hillside Overlay.


Light reflectivity value(LRV)is an objective qualitative scale measuring the relative
lightness/darkness of colors, where LRV of0 would be the darkest black, and 100
would be the brightest white. It is currently employed(LRV 60 max)in the West
Valley (di) combining district. Except during the time the house is being built, it is
difficult to implement paint color restrictions. Painting a house does not require a

permit, so in the absence of a design review condition, many homeowners would have
no reason

to believe a paint color limitation applies to them.

Los Gatos: LRV 30 or lower. Los Gatos Hillside Development Standards and

Cupertino: LRV 60 or lower, low-contrast earth-tone or vegetation colors. City of
Cupertino Zoning Ordinance, Sec 19.40.070.

Woodside: No LRV specified. Requires non-reflective building materials, emphasis
of(or integration of) natural wood and stone, low-contrast colors that blend with the
natural setting. Town of Woodside Residential Design Guidelines.


A survey of viewshed ordinances in cities in San Clara County and other California cities.


James T. Beall, Jr.

Content Type


Resource Type





District 4




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