A hydrology and hydraulic study of Russian River and Sergeant Creek presented Thursday to the Kodiak Island Borough Assembly concluded that Sergeant Creek Road is at high risk of frequent overtopping and that targeted work could substantially reduce that risk.

The study, led by River Focus and presented by river restoration engineer Jess Straub, was funded through a FEMA hazard‑mitigation grant administered by the Alaska Division of Homeland Security and Emergency Management and carried out for the borough. River Focus submitted a final report in August 2025 and presented findings publicly as required by the contract.

The report found that during modeled 5‑year flood events water overtops Sergeant Creek Road and produces velocities and depths that exceed safe driving limits; modeled 100‑year events produced multiple feet of overtopping. "Sergeant Creek Road, being the one road in and out, is of high risk with really high consequences if it fails," said Jess Straub, River Focus river restoration engineer. Straub told the assembly the models showed channelization at bridge constrictions and secondary channels that can trap flow and force water over low points in the road.

Why it matters: Sergeant Creek Road provides the single vehicle access for parts of the Women's Bay/Sergeant Creek community. If the roadway overtops or is damaged, access for residents and emergency services would be impaired.

Key findings and options
- Data and confidence: River Focus used available terrain (noting the borough's 5‑meter resolution terrain for parts of Women's Bay), cross‑section surveys, USGS regression estimates for discharges where gauge records are not transferable, and NOAA tide data (mean higher high water) for tailwater control. Straub cautioned confidence on some flow magnitudes is limited by lack of long‑term stream gaging in the watershed.
- Top alternatives: Modeling showed that raising (filling) the low portion of Sergeant Creek Road could maintain passage up to the modeled 100‑year event. Adding a horizontal floodplain culvert through the road alignment also reduced overtopping in modeled scenarios. Increasing conveyance under the state highway at the downstream crossing (a DOT decision) would further reduce upstream overtopping and improve systemwide sediment and flow passage.
- Property protection options: For Russian River's “dark side” (private‑property side), the study evaluated armored guide banks and other bank stabilization measures to reduce bank loss. Straub called hardened guide banks a potentially temporary and costly option; River Focus estimated a benefit‑cost ratio (BCR) under some assumptions below 1 for full armored solutions but above 1 for culverts and road raising in preliminary BCRs presented in the report.

Assembly discussion and next steps
Assembly members and staff discussed material sourcing for armor rock and the high cost of producing and placing large riprap. Assembly member Bo observed that locally sourced armor rock would be most cost‑effective but noted production is intentionally different to produce larger riprap, which increases cost.

Manager Amy Williams confirmed the borough has been sharing study data with Alaska Department of Transportation and the department "has it," as part of continuing coordination on highway work and future bridge/highway design.

Straub and the assembly urged pursuing funding for design and construction: "You can take this analysis and use that to secure funding for real design and start tackling these risks," Straub said. River Focus recommended using the report to pursue state and federal funding (including FEMA) and urged additional terrain data (for example, airborne lidar) and further watershed‑scale work to address sediment transport and channel behavior upstream of the study area.

No formal assembly action was taken on the recommendations at the work session; River Focus presented findings and the borough staff will close out the contract and pursue next steps, including potential grants and DOT coordination.

Ending: River Focus said it is available to present the findings to the Bells Flats/Sergeant Creek community; Straub told the assembly she was "open for that" and would coordinate with borough staff to arrange a community meeting. The manager and multiple assembly members stressed the importance of coordinating with DOT on any highway/bridge design that could change regional flood conveyance.