Marin County encompasses an unusually diverse landscape of redwood and Douglas-fir forests, oak woodlands, chaparral, coastal grasslands, estuaries, and developed communities. Its extensive open spaces are managed by federal, state, county, municipal, and local entities, creating a complex setting for wildfire prevention and emergency response.
Connecting these lands is a network of fire roads that allows engines, water tenders, firefighters, and other emergency personnel to reach wildland incidents. Although the roads cross jurisdictional boundaries, land managers previously lacked a consistent countywide understanding of where the most critical routes were located and whether they remained accessible to emergency vehicles.
More than 1,000 miles of unpaved roads extend across Marin County. Spatial Informatics Group worked with Marin Wildfire Prevention Authority, Panorama Environmental, and GreenInfo Network to inventory and assess over 500 miles of the highest-priority routes.
These roads serve multiple purposes, including fire prevention, utility access, land management, and recreation. Each route also presents distinct operational and environmental considerations. The assessment therefore went beyond mapping road locations to document the conditions that could delay or prevent access during an emergency.
Field crews recorded vegetation encroachment, erosion, damaged road surfaces, drainage problems, failing culverts, downed trees, gates, and other features that could affect vehicles or personnel. The objective was to identify these constraints before a wildfire occurs so they can be incorporated into maintenance and emergency planning.
Weather, remote access, diverse ownership, and changing road conditions made the field effort more complex than a conventional inventory so SIG technicians conducted the surveys using electric mountain bikes. E-bikes allowed crews to efficiently cover steep, narrow, gated, and degraded routes that would have been difficult to navigate with pickup trucks or utility vehicles. They also provided a low-impact approach suited to environmentally sensitive lands and areas with restricted vehicle access.
Technicians carried tablets equipped with ESRI Field Maps. When they encountered an obstruction or maintenance concern, they recorded its geographic location, photographed the feature, and entered detailed field notes. The information was then synchronized with a central geospatial database that all parties could utilize.
This field-based approach delivered more than a map of the road network. It created a detailed record of the condition and accessibility of individual road segments throughout the county that could be incorporated into Incident Management Software, like Tablet Command, and used to prioritize and plan improvements and maintenance.
By evaluating these conditions segment by segment, the project identified specific choke points and access limitations that may require maintenance or repair before the routes can reliably support wildfire response.
That additional detail strengthened the assessment. Rather than assigning a general condition to an entire road, the resulting database documents localized problems that can be reviewed and addressed individually. This allows agencies to distinguish between routes requiring routine vegetation management and those with more substantial erosion, drainage, gate, bridge, or structural concerns.
The survey found that vegetation growth, erosion, and deferred maintenance had narrowed some road segments over time. In certain locations, roads originally constructed and mapped as roads were becoming single-track trails. A route may still appear usable on an existing map even when its current condition would prevent a fire engine from passing.
The completed inventory provides the foundation for a countywide road-health and accessibility database that can be updated as conditions change and maintenance work is completed.
As the database is refined, MWPA and its member agencies will be able to identify priority maintenance needs and direct funding toward specific locations. Potential actions may include brushing roadside vegetation, restoring road and overhead clearance, repairing culverts and erosion damage, improving gate access, and addressing critical bridge or road deficiencies.
By combining field expertise with modern GIS technology, the Marin Countywide Fire Road Inventory and Assessment creates a shared and actionable picture of the county’s critical access network. The result is more than a map: it is a planning tool that can help agencies complete preventative maintenance, coordinate across jurisdictions, and keep essential routes ready for the next wildfire emergency.