Los Altos Hills


The Town of Los Altos Hills is a small residential community in the foothills above Los Altos in the western portion of Santa Clara County. With a population of 7,902, Los Altos Hills is one of the smaller communities in the County, dedicated to "preservation of the rural atmosphere of the foothills and orderly and unhurried growth."

Shared Responsibilities

Most policies guiding development and use of resources in Los Altos Hills are contained in the City's General Plan. With the understanding that their roles and responsibilities often intersect, the District and the City work together on many key community interests. Water resource-related goals and policies outlined in the City's general plan include:

  • Restoring major drainage courses to their natural condition insofar as possible
  • Protecting groundwater from adverse impacts
  • Reducing non-point source pollution in urban runoff
  • Implementing Flood Plain Management provisions
  • Preserving the integrity of riparian corridors

Looking forward, further collaboration or partnership will facilitate sustainable development in the region, particularly in the following areas:

When evaluating land use decisions:

  • Assess and plan for changes in water demand and storm water management, especially taking into account how urbanization affects the water cycle.
  • Decrease the demand for water.
  • Expand water use efficiency in existing and new development.
  • Actively pursue and facilitate the use of recycled water.
  • Protect and expand local water supplies.
  • Protect groundwater basins and source water protection zones.
  • Reduce flood risk.
    • Site new construction to assure stable stream channels and minimize flood risk.
    • Require that new construction in flood prone areas be built to flood safe standards.
  • Protect natural stream functions.
    • Restore fisheries, riparian habitat, and wetland areas.
    • Explore opportunities for increased creek-side trails and open space.

During operations of existing facilities or services:

  • Manage local storm drainage systems with stream capacity to contain floodwaters.
  • Support measures to reduce the exposure to flood risk.
  • Support measures to enhance flood preparedness and knowledge of risk exposure.
  • Prepare critical facilities for operations during flood events or prolonged draught.
  • Reduce pollutants entering streams.


The interactive map below shows the location of Los Altos Hills and illustrates some of the city's key features, such as major creeks, flood zones and groundwater subbasins.

To view key features, choose a layer from the "Select a layer to display" menu on the map below. You can select multiple layers to view at one time; if you wish to turn off a layer, select it again from the menu. Individual layers contain specific data that you can access by clicking on the layer itself.



Key Water Resources Features

Los Altos Hills transects the Permanente, Adobe, Barron and Matadero watersheds. Major creeks within the city limits include Adobe Creek, Barron Creek, Matadero Creek, Deer Creek, Dry Creek, Purissima Creek, Hale Creek, Magdalena Creek and the Summerhill Channel. Lakes include Quarry Lake.

Water Supply

Los Altos Hills’ drinking water is supplied by California Water Service Company and Purissima Hills Water District, which obtains its supply from San Francisco’s Hetch Hetchy system. The District supplies water for Los Altos Hills to the California Water Service Company via pipelines from the Rincoñada treatment plant. During the dry season, the plant and pipelines are at capacity.

In 2007, the town adopted a comprehensive set of policies aimed at protecting and conserving water resources. These policies include many recommended by the District in it Watershed Stewardship Plan, and emphasize the importance of water conservation and efficient use.

Flood Protection

Los Altos Hills' storm drainage system is designed to maintain natural water drainage patterns to the greatest extent possible. The Town has been working with the District to minimize flooding along flood prone areas, particularly Adobe Creek. The town's Municipal Code includes Flood Plain Management provisions to avoid new development in natural flood plains.

Watershed Health

The Conservation Element of the town's General Plan states:

Creeks and their associated riparian corridors are important public assets that provie unique ecological, aesthetic, an drecreational values to the community. The Los Altos Hills stream system contains some of the most intact and valuable riparian habitat in the San Francisco Bay region. ...Creeks and riparian areas are critically important as wildlife habitat and migratory corridors.

In acknowledgement of the importance of riparian areas, the town outlines a comprehensive set of conservation policies, including requiring 25-foot setbacks and open space easements along creeks and compiling a comprehensive riparian policy for property owners.

Citywide Programs and Projects

The City and the District collaborate on projects to maintain the health of the watershed and water quality, establish natural flood protection and provide access to open space and trails. Recent projects include:


Related Plan Elements

The Related Plan Elements listed below identify some of the District strategies  applicable to the city. They provide the basis for cities to provide better management of key water resources features within their jurisdictions and to work more effectively with the District to address water resources managemenet issues.

Related Plan Elements

District Has Primary Jurisdiction
E- Identify existing stream conditions and stream characteristics and implement practical solutions where appropriate, to improve stream stability and its dynamic equilibrium. (P)
District Collaborates
E- Provide flood frequency and forecast services. (C)
District Advocates
E- Promote removal or abandonment of infrastructure located within floodplains. (T)
District Advocates
E- Assist in the incorporation of flood-wise design features (e.g., minimize imperviousness, preserve natural drainage, rain harvesting and provide flood water detention) within the watershed. (T)
District Advocates
E- Encourage and provide technical assistance in mitigating erosion, sedimentation and high flows from new development or redevelopments. (T)
District Collaborates
E- Identify and incorporate stream rehabilitation measures into capital projects and operations to avoid, minimize and/or impacts to watersheds, streams and natural resources. (P and C)
District Advocates
E- Provide information on stormwater management and design of floodplains and channels. (T)
District Collaborates
E- Work with other entities for planning, design, construction, maintenance, and operation of trails/open space amenities.