Article 4 [1] – May 2026 – Gale Vick [2]
When is a “fish friendly” culvert a potential hidden salmon killer? When it is not monitored for damage or blockage.
Ever watch a Spring break up on an Alaskan river? Or a flood event? Or an embankment collapse? Whether on the mighty Yukon or a small stream off the Koyukuk, these are routine events and that usually means debris, and lots of it, getting jammed up somewhere. If it’s an open river system, out-migrating fish smolt or in-migrating adults can generally navigate under the debris. But if that debris is jamming up a culvert, it might as well be a brick wall to a fish.
Photo courtesy of Dr. Erik Schoen, University of Alaska-Fairbanks, July 2025. Chinook parr trying to navigate a blocked culvert as they head downstream on the North Fork of the Chena River at 42 Mile on Chena Hot Springs Road. The grate was subsequently lifted sometime later that summer after being reported.
Culvert maintenance is just as important as the culverts themselves when it comes to protecting fish passage. Even the best culvert designs can get damaged or blocked. Alaska has a really tough time maintaining our roads much less our culverts and that’s a serious problem for migrating salmon.
An ecologist friend, Dr. Kevin Fraley, with the Wildlife Conservation Society, travels and works throughout northern Alaska and recently sent me an example. “The “Road to Tanana” [3] was built in 2016 by the State of Alaska to connect the end of the Elliot Highway to the Yukon River just upstream of the Village of Tanana, Alaska. This 50-mile road cost nearly $14 million to build. It is an apt example of how lack of maintenance effort and funding can negatively affect fish passage along northern Alaska roads. Maintenance for the road is tasked to a small DOT [4] outpost at Manley Hot Springs, and the road has suffered frequent washouts, culvert failures, and is commonly impassable to vehicle traffic due to lack of maintenance effort and funding. As early as 2021 the road was impassable due to a large failed culvert. This was in the Spring time when juvenile salmon could be attempting to migrate downstream, and is a time period when culverts commonly fail due to high water from snowmelt runoff. The culvert was bent and perched from the freezing and thawing cycle, which occurs every year, and was potentially blocking fish passage. Similarly, in 2025, the road became completely impassable (even for 4WD vehicles, I got my truck stuck and had to turn back) for most of the summer season due to poor maintenance with further faulty culverts and large amounts of road sediment being entrained into watercourses.”
Photo courtesy of Dr. Kevin Fraley, Wildlife Conservation Society. Tanana Road 2021.
This example sums up the magnitude of the culvert problem for fish and it definitely creates flashing neon lights for the proposed Ambler Road Project.
Culverts across fish-bearing streams should be examined several times between Spring break-up and fall freeze up. But that rarely happens. Currently Alaska has not been able to monitor culverts in an urban area, such as Fairbanks. Monitoring culverts in remote areas is a function of sheer happenstance or special projects. Debris carried by water systems, beaver activity, erosion, settling and collapsing roads, flooding, fire, human-caused damage and more are common everywhere in Alaska.
When a fish-friendly culvert is not maintained, it often transitions from a functional habitat connector into an impassable barrier for aquatic life. Lack of regular upkeep, such as clearing debris and monitoring structural integrity, leads to physical and ecological degradation that disrupts fish life cycles and harms the surrounding watershed. Just some of the consequences of neglected culvert maintenance in impacts on fish passage and habitat:
- Debris Blockages: Culverts snag woody debris, sediment, and trash. This creates physical clogs that prevent fish from moving upstream or downstream to feed, seek refuge, or spawn.
- “Perching” (Elevated Outlets): High-velocity water exiting an unmaintained or undersized culvert can erode the streambed at the outlet. This creates a vertical drop, or “perch,” that many fish—especially juveniles—cannot jump, effectively cutting off miles of upstream habitat.
- Increased Water Velocity: Clogs and sediment buildup narrow the passage, forcing water through a smaller opening. This increases water speed to levels that fish cannot swim against, particularly during high-flow events.
- Shallow Flow: Over time, sediment accumulation or improper slope maintenance can result in water levels too shallow for fish to navigate, leaving them exposed or unable to cross.
- Water Quality Degradation: Blocked culverts can cause “backwatering,” where water pools upstream and stagnates. This leads to increased water temperatures and decreased oxygen levels, both of which are detrimental to aquatic species.
- Sedimentation: Lack of natural sediment flow coarsens the downstream bed, destroying spawning gravel needed by salmon.
The failure to maintain culverts is repeated all over Alaska. The two biggest reasons? (1) Alaska doesn’t have enough money or manpower, and (2) we don’t know where all the culverts are. In comparison to the size of our state, Alaska does not have many roads or rail crossings but the ones that we do have still require thousands of culverts, although we don’t actually know how many. That’s because there is no master culvert data base covering federal, state and private lands. The Alaska Division of Geological and Geophysical Surveys (DGGS) and the Alaska Department of Fish and Game (ADF&G) Fish Passage Inventory Data Base (FPID) are utilizing reporting from the public to help identify culverts over stream crossings but this does not translate into actual monitoring. In addition, the Department has a caveat:
“ Interactive Mapping Liability Statement. The Alaska Department of Fish and Game (ADF&G) makes no guarantee concerning the data’s content, accuracy, completeness, or the results obtained from queries or use of the data. ADF&G makes no warranty of fitness for a particular purpose, no representation as to the quality of any data, and assumes no liability for the data represented here. These data do not represent exhaustive inventories, but are compilations of existing knowledge from field biologists that are updated periodically as knowledge improves. These data should be used cautiously because they are not exhaustive, and are subject to change. When conducting projects or planning for fish and wildlife, please consider using additional information gathered from field investigations and consultations with ADF&G or other professional biologists.” [5]
Alaska has really neglected the immense role that culverts play among the major declines factors of salmon. It is way past time that we had a discussion about how to assess the costs of culvert maintenance for every single culvert on a fish bearing stream.
Part 5 of this series will discuss who pays for culvert maintenance and repair and estimates of long-term costs.
References:
[1] Part 1 of this series discussed the general risks to salmon species in the Ambler Road Project area . Part 2 discussed how culverts impact fish passage. Part 3 discussed general costs of culvert installation and what that could mean to the Ambler Road Project.
[2] Gale K. Vick is a 57 year resident of Alaska with a long history of research and commentary on fisheries policy for various organizations. This is researched opinion and should not be considered definitive. Original sources should always be consulted and verified.
[3] https://dot.alaska.gov/nreg/tanana/
[4] Alaska Department of Transportation
[5] https://www.adfg.alaska.gov/index.cfm?adfg=fishpassage.database