• Field walking assessments with geologist to evaluate stability from geological and hydrologic perspectives.
• Fluvial geomorphic assessment of stream crossings
• Erosion and sediment yield assessments for identified road and trail segments
• Integrated mapping of geologic units, soil types and road/trail segments
• Recommendations for stable replacement trail segments and for unstable stream crossings.

Clearwater Hydrology (CH) was retained by Leonard Charles & Associates to prepare an erosion and sediment yield assessment for the Cascade Canyon and White Hill Management Plan in Marin County. The open space is managed by the Marin County Open Space District. The Plan presented a prioritized listing of recommended mitigations to stabilize deteriorating segments of preserve fire roads and trails, and to minimize the delivery of eroded sediments to San Anselmo, Cascade, Fairfax and Carey Camp Creeks, as well as their intermittent tributaries. These four creeks were identified by the National Marine Fisheries Service (NMFS) as critical habitat for Central California Coast steelhead (Oncorhynchus mykiss) and Central California Coast coho salmon (Oncorhynchus kisutch).

To accomplish the work an overlay of the trail system on a soil survey map was developed to determine soil types at the locations of the various road and trail segments. The Universal Soil Loss Equation method for estimating sediment loss from hillslopes or open fields was used for estimating potential soil loss due to erosion under conditions of hiking, bike and equestrian use. Sediment yield to park streams was then computed based on appropriate sediment delivery ratios. Based on the results of the assessment, CH recommend mitigation measures that in conjunction with the proposed trail additions and closures would result in a net decrease in both the erosion of soil from trail and roadway segments and the delivery of eroded sediments to active channels.

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