Arroyo Sausal heads at about 789 feet (240 m) and flows northwest, crossing Point Reyes-Petaluma Road into Hicks Valley then west to Soulajule Reservoir.

[6][7] The California Office of Environmental Health Hazard Assessment has issued a safe eating advisory for any fish caught in Soulajule Reservoir due to elevated levels of mercury and PCBs.

In the early 1900s, coho salmon (Oncorhynchus kisutch) were abundant in Walker Creek, but were nearly extirpated apparently due to severe erosion and siltation secondary to potato farming, overgrazing and logging operations.

He found small numbers of steelhead young-of-the-year in all viable habitat areas in the watershed, but only eight coho near the confluence of Chileno and Walker Creek.

Portions of Keyes Creek immediately downstream of the present Highway One bridge were once navigable and used to ship locally-grown potatoes by barge to San Francisco.

The current small size of the channel at this location, more suitable for a canoe than a barge, is dramatic evidence of siltation due to erosive agricultural practices(potato farming) in the Walker Creek watershed over the past 150 years.