Hungrary Creek and Little Grizzly Creek Subwatersheds
Prepared for Plumas Corporation
Ken Roby
Feather River Chapter, Trout Unlimited
December 2023
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Executive Summary
Surveys of road crossings were conducted in the Hungry and Little Grizzly Creek subwatersheds. Both
streams lie within the Tributaries Forest Recovery Project. Each provide important spawning habitat for
native trout in Indian Creek, and important recreational fishery.
Survey results found numerous road segments in need of improvement, with a small percentage of road
crossings delivering a majority of sediment to channels. Road crossings where flow from channels had
been diverted down roadways as a result of plugged culverts accounted for the greatest percentage of
sediment delivery. Road surfaces with long delivery paths on relatively steep road grades were another
primary sediment source. In Hungry Creek, over 90% of estimated sediment production came from 10
sites (of 59 surveyed). In Little Grizzly Creek, over 90% of estimated sediment production came from 11
of 94 sites surveyed. A high percentage of crossings (31% in both Hungry Creek and Little Grizzly Creeks)
were identified that have the potential for road capture of streams if the crossing were to fail. No
problems were identified in any of the ten low water crossings surveyed.
A high percentage of crossing approaches (67% in Hungry Creek, 50% in Little Grizzly Creek) exceed
current California State Practice Rules guidelines for connected length of approaches. Cumulative
connected approach lengths increased flow paths by 3.3 miles in Hungry Creek and 4.4 miles in Little
Grizzly Creek.
Few crossings in either subwatershed meet the current direction of culvert sizing to pass 100 year return
interval flows, bedload and debris. 21% of culverts in Hungry Creek and 25% in Little Grizzly Creek are
adequately sized for 100 year storm events. Only one culvert (in Hungry Creek) is sized to carry bedload
and debris along with a 100 year flow.
Twelve channels above road crossings were identified that could benefit from the addition of standing
dead trees to provide downed large woody debris.
Priority Recommendations for improvement fall into three categories:
- Maintenance of crossings where culverts are completely or substantially plugged to prevent
additional stormflow damage. - Storm proofing of road crossings and approaches, including construction of critical dips and
construction of additional drainage structures to reduce length of connected road surfaces. - Development of an approach to upsize culverts, or replace culverts with low water crossings at
priority crossings. - Revision and implementation of revised road management objectives for road 24N08X, an
ummantained spur in Little Grizzly subwatershed where numerous road crossing caused
problems were found.
Acknowlegments: FRTU thanks Gary Rotta and Wayne Cartwright for assistance in conducting road
surveys. We also thank the US Forest Service for support in map preparation. Data analysis and report
preparation were supported by a grant from The Rose Foundation.