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Watershed, Flood-Risk, and Infrastructure Assessment Coordination - Deputy Director Riske-Gomez
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Requested Action(s)
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Informational presentation on TCTC’s ongoing coordination with Public Works - Flood Administration, the Resource Conservation District (RCD), and State and federal partners regarding watershed-driven transportation impacts and the development of a countywide infrastructure risk assessment.
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Financial Impact:
None.
Background Information:
Over the past several years, Tehama County has experienced increasingly severe transportation impacts tied to storm events, altered watershed behavior, and accelerated geomorphic change. These impacts are no longer isolated maintenance issues; they reflect a systemic shift in how water, sediment, and debris move through our landscapes, influenced by post-fire conditions, invasive vegetation, agricultural grading, and over a century of controlled irrigation and flood manipulation.
Transportation impacts in Tehama County are no longer driven solely by storm intensity. Increasingly, they reflect the interaction between anthropogenic modification and modern flooding dynamics, the combined influence of altered floodplains, agricultural grading, regulated river systems, vegetation shifts, and post-fire watershed response. These factors shape how water and sediment move through the county today, producing failures that exceed the design expectations of legacy infrastructure.
The Reeds Creek Road Emergency Repair Project represented a turning point in our understanding of these risks. Repeated channel migration, debris loading, and sediment deposition led to major roadway failures and long-duration access disruptions. Reeds Creek made clear that watershed-scale processes, not local culvert conditions, now dictate the reliability of key transportation corridors.
Since then, multiple storm-driven failures across the county have confirmed that this is a countywide pattern, not a single-corridor anomaly. These events demonstrate how today’s hydrology interacts with legacy infrastructure, historic land management, and increasingly volatile weather cycles. Even moderate storms are producing outsized impacts, overwhelming facilities designed for historic conditions and triggering failures in both valley-floor and foothill systems.
Since then, multiple verified storm-driven failures have highlighted the countywide nature of the risk:
Documented Transportation Infrastructure Failures
• 2019 - Squaw Hollow Creek @ Corning Road (Bridge Damage):
Heavy rainfall on February 27, 2019 caused upstream bank erosion and damage to the wingwall and abutment, washing out the roadway and requiring emergency embankment reconstruction and rock slope protection.
• January 2023 - Burch Creek (Bridge Collapse):
Floodwaters caused Abutment 1 to fail, resulting in the collapse of Span 1 into the channel. Caltrans recommended immediate full closure, and the County closed the bridge for safety.
• February 2025 - Kendrick Creek @ Newville Road (Bridge Closure):
Following significant storm damage, the County formally closed the bridge due to structural deficiencies aggravated by high-flow events and erosion.
These events confirm that Tehama County is experiencing recurring, watershed-driven structural failures affecting roads, culverts, bridges, and embankments. Beyond the documented failures at Squaw Hollow Creek (2019), Burch Creek (2023), and Kendrick Creek (2025), Tehama County is experiencing broader watershed-driven degradation of transportation assets.
Recurrent storm events have produced bank failures at Woodson Bridge, overtopping at Elder Creek and Dibble Creek, high-velocity erosion along Antelope Creek, river migration impacts near Jelly’s Ferry Road, and localized bridge and culvert vulnerabilities on rural facilities such as Cone Grove Road. These conditions illustrate a countywide pattern in which storm hydrology, sediment transport, and post-fire watershed changes are directly affecting roadways, embankments, and bridge structures.
Role of Non-Profits, County Departments and TCTC
While watershed processes fall within the technical expertise of Public Works - Flood Administration, their responsibilities apply specifically to County-owned flood management facilities and public infrastructure, not private lands. Partnering with the Resource Conservation District (RCD) allows the County to better engage private landowners and support collaborative, long-term watershed stewardship solutions that reduce downstream impacts on public roads and critical access corridors.
Because many watershed-driven impacts originate on private or upstream lands but ultimately manifest as failures on the transportation system, TCTC must participate directly. Transportation planning, interagency coordination, and long-range capital programming are core Commission responsibilities, and safe mobility and emergency access depend on understanding how these evolving watershed conditions interact with roads, bridges, culverts, and evacuation routes.
TCTC’s role is therefore not to manage watersheds, but to ensure that transportation decision-making is aligned with hydrologic realities and that State, federal, and local partners are coordinated in developing durable, long-term solutions for the region.
State-Led Multi-Agency Technical Assessment
In response to Tehama County’s request for assistance, Cal OES has convened a multi-agency team including:
• California Department of Water Resources (DWR)
• California Geological Survey (Department of Conservation)
• Caltrans Emergency Operations
• U.S. Army Corps of Engineers (technical coordination through Readiness Branch)
• Cal OES Inland Region
• Tehama County Public Works - Flood Administration
• Tehama County Resource Conservation District
This team will lead a comprehensive watershed and infrastructure vulnerability assessment, addressing:
• Post-fire hydrology
• Sediment transport and deposition patterns
• Channel migration and erosion risks
• Vulnerabilities in roadways, culverts, bridges, and river-adjacent facilities
• Prioritized mitigation and funding strategies
Tehama County is still awaiting determination regarding inclusion in the State disaster proclamation, which may further strengthen access to State and federal resources.
The first coordination meeting with the team was held the third week of December, with follow-up work commencing in early 2026.
Desired End Project Product Description: Tehama County Resilient Transportation Hazard Screening & Prioritization System
As we continue to face more frequent wildfires, flood events, debris-flow impacts, and drainage failures, it has become increasingly clear that Tehama County needs a consistent, data-driven way to evaluate risk across our entire transportation network. The end product we are working toward is a countywide, GIS-based hazard screening and prioritization system that will allow the Commission to clearly identify where our greatest vulnerabilities are, and which projects should rise to the top for funding, planning, and emergency preparedness.
What the System Will Provide
The ideal completed tool will give the Commission:
A countywide map of transportation “hot spots,” areas where roads, culverts, or bridges are most at risk from post-fire debris flows, sediment bulking, flooding, riverbank erosion, or repeated storm failures. This information will be made available to first responders, emergency managers, public works crews, planners, and decision-makers so they can anticipate where failures are most likely to occur, stage resources appropriately, plan detours, and prioritize mitigation actions before and after major events.
A defensible priority ranking of transportation assets, based on hazard, exposure, and consequence, allowing us to clearly identify tiers of project needs.
An interactive ArcGIS On-Line (AGOL) dashboard that Commissioners and partner agencies can view, showing risk levels at each site, the number of residents affected, detour distances, and whether a segment serves as an evacuation route or sole access point.
A repeatable workflow that can be updated after any future wildfire or storm event, ensuring the Commission has the most current information for disaster response, planning, and grant applications.
Why This Matters for the Region
This system will give us, for the first time, a unified, countywide picture of transportation vulnerability, grounded in the same scientific methods used by Cal OES, CGS, DWR, USGS, and Caltrans. It strengthens our ability to:
Prioritize limited transportation dollars
Build competitive, data-supported grant applications
Coordinate across agencies during emergencies
Plan long-range resilient infrastructure improvements beyond fire planning alone
Demonstrate clear need to state and federal partners
At the end of this effort, the Commission will have
This effort is a natural continuation of the County’s Secondary Access Planning work, expanding that same forward-looking approach into a comprehensive, countywide understanding of transportation vulnerability. The goal is to develop a single, authoritative tool that identifies our highest-risk transportation locations, ranks project needs, supports funding decisions, and provides a clear roadmap for improving safety and resilience throughout Tehama County.
The resulting system will not only highlight areas most at risk from post-fire debris flows, sediment bulking, flooding, river erosion, and repeated storm failures, but will also provide actionable information to first responders, emergency managers, public works crews, planners, and decision-makers. By knowing where failures are most likely to occur, agencies can proactively stage resources, plan detours, coordinate emergency response, and prioritize mitigation.
This tool will serve as a foundational component for future planning documents, resilience investments, and interagency coordination. It also positions the Commission to significantly enhance competitiveness for state and federal funding by demonstrating a clear, data-driven understanding of where infrastructure improvements are most urgently needed and how they support community safety, mobility, and emergency preparedness.