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Summer 2006
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Online Only Article The Agua Caliente Indian Reservation of Riverside County, California

The Role of Tribal GIS in the Protection and Promotion of the Canyons

By Sheila Gehani, GIS Manager, Agua Caliente Band of Cahuilla Indians

  click to enlarge
  click to enlarge
Tribal GIS map shows the beginning and end of a planned reconnaissance route along East Alexander trail with one-quarter-mile markers.

The Agua Caliente Indian Reservation takes pride in its lands. Tahquitz Canyon, California, is listed in the National Register of Historic Places. The Indian Canyons contain the largest naturally occurring stand of California fan palms in the United States. All the tribal land canyons contain important biological and hydrological resources, sensitive plant and animal species, and are of cultural and historic importance to the Agua Caliente Tribe. GIS is put to many uses by the tribe in managing tribal lands and supporting programs.

The Agua Caliente Indian Reservation is a 32,000-acre checkerboard reservation located in Riverside County, approximately 100 miles east of Los Angeles. The western/southwestern half of the reservation lies within the rugged Santa Rosa and San Jacinto Mountains National Monument, and the eastern half lies within the Palm Springs metropolitan area. The canyons under tribal jurisdiction are Tahquitz Canyon, the Indian Canyons, and parts of Chino Canyon. Tahquitz Canyon and the Indian Canyons are ranger managed and open to the public with admission.

The tribal GIS team provides support to tribal planners, scientists, technicians, and consultants performing research and conducting projects in the canyons and also to canyon crews doing inventory and maintenance work. In addition, the tribal GIS team prepares maps and guides for visitors to the canyons.

In 1998, based on need and at the tribe's request, the Bureau of Land Management (BLM) conducted a survey of the Indian Canyons to locate and/or recover monumentation. In surveying, monumentation refers to the practice of marking down horizontal and vertical control points with permanent structures. Once surveyed, these monuments can be used for further surveying and the alignment of land parcel boundaries and infrastructure.

BLM used historic descriptive records and calculations to find the Public Land Survey System corner and quarter-corner monuments and markings. Canyon crews assisted with the foot surveys over rugged terrain. GPS coordinates were collected, and data was transferred to tribal GIS. With the resurveyed coordinates, tribal GIS has been able to refine reservation and property boundaries in areas where sparse development does not warrant county and local governments undertaking this task.

Each summer, tribal rangers conduct condition surveys and maintenance inspection of trails. Tribal GIS staff members use ArcGIS Desktop software (ArcView and ArcInfo) to provide rangers with trail maps annotated at intervals where inspections are conducted.

Tribal consultants and academic researchers have surveyed and continue to survey the riparian areas of the canyons and identify vegetation communities and wildlife species that reside within these communities. On conclusion of these surveys, the tribal GIS becomes the repository of the survey location data and reports.

"Having the GIS as a repository for species data from annual field surveys," states Margaret Park, director of planning for the Agua Caliente Band of Cahuilla Indians, "is helping us create a strong set of baseline data about the endangered species that call the canyons home."

  Tahquitz Canyon waterfall
Tahquitz Canyon waterfall

Tribal GIS is responsible for integrating this data within an ArcSDE software-managed geodatabase system and associating spatial and tabular datasets. Tribal GIS staff members provide the Planning and Development Department with maps, tables, and charts.

To comply with the mandates of the National Fire Policy and Plan, the tribe is in the process of establishing a fire management plan for the reservation. The canyons' maintenance crew regularly surveys the trails and surrounding environment for litter and stressed vegetation. Tribal rangers use ArcPad to collect data with handheld GPS receivers. High-resolution aerial imagery provides the backdrop for rangers to annotate fuels, debris, and invasive species tagged for mitigation or removal. The data is brought back to the GIS crew that prepares the maps and reports for management review. Park says, "The ability to accurately track our progress in removing fire fuels and invasive species makes our grant-reporting tasks quicker and easier."

Six streams in the canyons are gauged for water quality and quantity monitoring. These springs, along with others, are visited and sampled biannually. Changes in vegetation and trail conditions that could impact water quality are also monitored. Tribal GIS staff members work closely with the tribe's hydrogeologist and environmental technician to provide aerial images and maps showing riparian features. Arc Hydro was used to reconstruct intermittent stream channels from a detailed digital elevation model (DEM) of the canyons. Stream gradients were calculated along stream intervals in riparian areas. This information provides input to flow and channel roughness calculation models and verifies gauging instrument output.

Twenty-five sensitive species of wildlife either migrate through or reside in the canyons. Tribal rangers and field technicians record sightings, nests, tracks, audible clues, and even the presence of predatory animals and birds to determine the presence of a particular species. Academic and environmental consultants regularly survey wildlife. On conclusion of these surveys, data and reports are received by the Planning and Development Department. The data and information are stored in the geospatial database. Species observations and habitat data collected by the California Department of Fish and Game, consultants to the county, and local agencies are also included in the database.

The tribe has adopted a habitat conservation plan and established the Indian Canyons Heritage Park and Tahquitz Canyon Wetland Conservation Area and plans for their protection and management. In rugged terrain, where accessibility is limited, tribal GIS staff members have been able to use high-resolution aerial imagery and a five-foot DEM to provide tribal planners with slope, viewshed, density, area of effect, and other models, data, and maps to aid in their day-to-day planning activities. Future activities for habitat protection could include real-time tracking of collared species with ArcGIS Tracking Analyst.

GIS has a role to play in a detailed vegetation analysis planned for the future. Analysis of remotely sensed multispectral/hyperspectral imagery is being considered.

For more information, contact Sheila Gehani, GIS manager, Agua Caliente Band of Cahuilla Indians (e-mail: sgehani@aguacalente.net, tel.: 760-883-1336).

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