The policies and programs in the Environmental Hazards Element reflect recent legislation and research on geologic, seismic, flood, and fire hazards.

Marin County is at risk for a number of geologic hazards, including but not limited to landslides, debris flow, liquefaction, and differential settlement. These geologic hazards can be aggravated by seismic activity. The San Andreas Fault runs through West Marin and is the only known active fault in the county. Seismic activity on the San Andreas Fault poses a significant threat to lives and property since an earthquake could trigger landslides and other geologic events, flooding, and fire.

Flood hazards can originate from watercourses, reservoirs, bay waters, and coastal waters. Streams and creeks regularly swell with storm water runoff and inundate developed areas; dams located near the San Andreas Fault could rupture after an earthquake and cause flash flooding; high tides and storm swells can cause bay and coastal waters to rise and flood shoreline areas.

Fire hazards fall into two general categories: wildland fires, which emanate from open chaparral and grassland or forest areas and can threaten adjacent communities; and structural fires, which damage homes and workplaces and may spread to other areas.

Geologic hazards, fire, and flooding are a major concern. The risk of damage from these environmental hazards can be reduced through mitigation measures such as zoning, project review, public information, and coordination with other agencies.

The objectives, policies and implementation programs contained in this Element are intended to reduce the risk of death, injuries, damage to property, and economic and social dislocation resulting from flood, fire, seismic, and geologic hazards.