Foothills Open Space Acquisition Planning


WCA’s founding mission is to provide for a comprehensive program to expand and improve the open space and recreational opportunities for the conservation, restoration, and environmental enhancement of the San Gabriel and Lower Los Angeles Rivers Watershed area consistent with the goals of flood protection, water supply, groundwater recharge and water conservation. An integral part of this mission is to acquire and protect lands for watershed protection, conservation, natural open space, and recreational purposes.

San Gabriel Mountains and Foothills Regional Open Space Acquisition Prioritization Plan was initially conceived in 2016 by Watershed Conservation Authority and Trust for Public Land to guide WCA’s strategies for open space protection in the foothills. WCA also found it important to understand the resource management and operations factors that affect a public entity’s management of habitat and open space.

Since that time, extreme heat and drought, proliferation of invasive species, increased demand for recreational access, and the continuation of development in severe fire hazard zones, adds complexity to this work. The ecosystem services provided by our rare remaining open space lands is as important as ever. Such ecosystem service include biodiversity, stormwater capture and infiltration to increase local water supplies and reduce downstream flooding, and improving water quality in surface water bodies. 

Trust for Public Land identified more than one hundred parcels (several dozen parcel clusters) as strong candidates for acquisition due to general factors such as aggregate size of parcel clusters, undeveloped land, contiguity to other protected lands, real estate factors, and funding priorities. These recommended parcels became the basis for additional studies to clarify how biological, hydrologic, and cultural resources, human factors, fire threat, and management considerations should affect prioritization.

The San Gabriel Mountains and Foothills Open Space Acquisition Master Plan includes a suite of studies examining conservation priorities through the lens of diverse perspectives. The plan is currently being packaged along with additional interviews and analysis by WCA, into a condensed form for public sharing.

In 2024, WCA will present a series of online events to share the studies that contribute perspectives on the role of open space conservation in the San Gabriel Mountains Foothills. Online events will be supplemented by field excursions. A link to the schedule will be posted here when available.

In the meantime, the studies included are shared below:  

  • Coarse scale biodiversity metrics that account for factors associated with biodiversity were developed by Psomas. Scoring of these metrics was based on public data, and many of the metrics are based on relatively stable factors that influence a parcel’s contribution to the goals of the study. (Percentage of native vegetation cover, parcel size, adjacency to protected land, presence or proximity to special status species). These parameters were scored and weighted as appropriate to assign priorities for property acquisition.

  • On-the-ground “rapid field assessments” of potential priority parcels was conducted by Cooper Ecological Monitoring. These assessments add detail to the picture of biodiversity in the study area, and revealed recent trends as manifest in the landscape, and additional resources that should not be overlooked.

  • Geomorphic and Hydrologic opportunities in priority parcels. Balance Hydrologics created a prioritization based on the presence of hydrologic features on parcel clusters under consideration that might be expected to contribute to regional watershed management goals including headwaters and water quality protection, infiltration potential, longitudinal connectivity, and presence of riparian areas, seeps, and springs.

  • Existing Conditions and Restoration Opportunities in the San Gabriel River and Azusa Floodplain. Balance Hydrologics evaluated hydrologic and geomorphic factors that have potential to contribute to hydrologic restoration of the San Gabriel River mainstem, and to inform prioritization of open space acquisition.

  • Aquatic habitat assessment in the San Gabriel River mainstem. Stillwater Sciences assessed the current channel and floodplain conditions to understand how opportunities to improve aquatic habitat should inform prioritization of acquisitions.

  • Foothills Records Search and Sensitivity Analysis was conducted by Cogstone Resource Management. The records search included the original parcel clusters recommended by TPL as well as a ½ mile radius. Based on the results of this search Cogstone ranked the sensitivity of candidate parcels based on whether they have been previously surveyed for cultural resources, whether resources were found.

  • Cultural Sensitivity of 118 Parcels Located in the San Gabriel Mountain Foothills, is a more in-depth cultural sensitivity analysis by Cogstone Resource Management which includes discussion of the project area’s cultural setting, Tongva ethnography, village, trade and exchange routes, and the need to recognize the traditional Tongva concept of Maxaax, a reciprocal relationship to the land.



WCA served as a client for UCLA Master of Urban and Regional Planning candidates Zachary Zeilman and Matthew J. Mello on capstone projects that examine fire in the Wildland Urban Interface with a specific focus on the foothills of the Eastern San Gabriel Mountains:





The foothills of the San Gabriel Mountains are the interface between the first national forest, which was established to protect the water supply of the Los Angeles Basin, and the millions of people who inhabit the eastern Los Angeles Basin.

The San Gabriel River is a major regional water supply source whose headwaters are also important sites for recreation.

Critical water infrastructure along the San Gabriel River continues as a series of spreading basins downstream of the mountain ecosystems that are its headwaters. Almost all the water that falls in the San Gabriel Valley and mountains are captured by this infrastructure for percolation into groundwater basins.

With over ten million residents in the County today, the San Gabriel Mountains play an increasingly important role in offering opportunities for recreation, a respite from dense urban environments, and clean air and water.

The first national forest, the San Gabriel Mountains, was established for the protection of ecosystem services.

Protection of the San Gabriels (The San Gabriel Timberland Reserve) by President Harrison in 1892 occurred in response to public interest in protecting watershed values. At that time, the public was very engaged in watershed management issues. Settlers in the basin in the 1880s observed the direct causal relationship between extractive uses that degrade chaparral vegetation cover in the mountains (logging, unlimited cattle and sheep grazing, and burning to replace chaparral with grazing lands) and ensuing erosion, flood, and loss of the land’s ability to store water.