Evaluating Stream and Watershed Conditions in Northern California
The Fire and Resource Assessment Program (FRAP) developed a map based approach for watershed assessment that evaluates stream condition by considering factors relating to riparian habitat and potential sediment delivery. For this analysis stream gradient and streamside vegetation are used as primary indicators of riparian habitat. A classification of stream types based on channel morphology combined with information on potential recruitment of LWD, hillslope stability, and road related sediment provided the basis for a watershed assessment. Several indices were developed to represent the contribution of roads, timber harvesting and slope stability to sediment delivery in streams. Baseline data on riparian habitat and potential sediment delivery were used to develop a prioritization model that evaluates the restoration potential for each sub-basin. Using spatially explicit information from a Geographic Information System (GIS) the model identifies basins that are in need of short term sediment risk reduction, longer term forest stand improvements and existing habitat protection.
An assessment of the Noyo and Big River watersheds in Northern California revealed that 40% of the 900 miles of stream lengths analyzed were classified as low gradient response reaches. This represents the maximum amount of stream habitat that is potentially available to salmon. Analysis of vegetation in the riparian zone indicates that forests are dominated by mid seral stage trees. In forests bordering response reach streams, 23% of the area contains mature forests exceeding 24" dbh, while less than 10% of the area contains late seral stage forests exceeding 36" dbh.
The lack of late seral stage forests suggests that conservation of salmon habitat in these two river systems will be dependent on management of mid seral forests. The methods developed for this study provide a comprehensive, but coarse grained (i.e. level 1) assessment of watershed sub-basins. The results reflect the pattern of land use across two watersheds and suggest that the configuration of existing habitat versus potential sediment sources should be considered to insure the overall protection of the watershed.Read the full publication: Evaluating Stream and Watershed Conditions in Northern California (.pdf)
- Using GIS to Evaluate Watershed Condition (.pdf)
- A Map Based Approach to Watershed Assessment (.pdf)
CAL FIRE Fire and Resource Assessment Program (FRAP)
PO Box 944246
Sacramento, CA 94244-2460