by Stephen C. Conroy
To celebrate 27 years of publishing Whatcom Watch, we will be printing excerpts from 20 years ago. The article below appeared in the June 1998 issue of Whatcom Watch.
Editor’s Note: In 2013, federal court Judge Richardo Martinez ordered the state to fix barrier culverts. The state took the matter to federal court and lost, then appealed to the Ninth Circuit and lost again. They appealed to the U. S. Supreme Court and the court took up the matter. A decision should be issued before the current term ends in late June.
Many of Washington’s native salmon, trout, char and steelhead stocks are depressed. Some are already extinct. And some, especially coho, chinook and Columbia River bull trout, are candidates for listing under the Federal Endangered Species Act. With many other stocks and species on the path to extinction, we have to take action to protect the remaining stocks, and to promote the regeneration of the healthy wild fish habitats upon which our native fish stocks depend.
Unfortunately, in many places we are failing to provide even the most basic protection for our streams and salmon. This is partly due to a lack of county and state regulations requiring adequate streamside protection, especially in development and agricultural areas. However, there is a more insidious reason as well. Even when the laws are there to protect fish-bearing streams, the water type maps that are relied on to indicate which streams have fish in them are grossly inaccurate. Washington Trout’s stream typing research has found that, on average, the Washington Department of Natural Resources’ maps are incorrect more than 50 percent of the time. Hundreds of miles of streams do not even appear on the maps, and others are incorrectly deemed to have no fish in them. Streams that should be protected because of their importance to the survival of certain stocks are being degraded because of oversight and sloppy science. We are losing habitat every day, simply because of bad maps.
Studies by tribal biologists in the Olympic Peninsula and Hood Canal areas showed that current Department of Natural Resources water type maps underestimate the actual miles of fish-bearing streams by almost 50 percent
In the Snoqualmie drainage, over 40 percent of the new fish-bearing streams that have been identified were not even present on Department of Natural Resources’ base maps! This constitutes over 30 miles of fish-bearing water, in a single drainage, that were not afforded appropriate protection in law because the Department of Natural Resources did not know they were there.
Fish Found in Small Streams
The Department of Natural Resources set standards of minimum width and maximum gradient for a presumption of fish presence. Data from field surveys have shown these criteria to be grossly inadequate. Fish, both resident and anadromous, are frequently found in streams as small as two to three feet wide at the ordinary high water mark. The actual wetted width of some of these streams can be as little as one foot in the dry season, and some streams that contain important spawning habitat actually dry up in summer. State agencies are now recognizing that these tiny streams can in fact be fish-bearing and may actually constitute critical spawning and rearing habitat for cutthroat trout and coho.
In recognition of the magnitude of the mis-typing problem, the Timber, Fish and Wildlife process has implemented an emergency ruling designating that all streams currently typed as “four” [non-fish bearing] be treated as fish-bearing under the Forest Practices Rules, providing they are wider than two feet at the ordinary high water mark and are of 20 percent or lower gradient. This will in fact afford higher “Type three” riparian protection to the vast majority of fish-bearing water currently typed as “four.”
Major Factor in Decline of Fish Populations
What is a major contributing factor to habitat loss and degradation and a factor that may be the most common limiting feature in the decline of fish populations in most of our streams? We are talking about culverts.
When streams are typed incorrectly, they are then given no protection under the law. This means that not only are the adjacent lands left open to abuse, but developments in the streams, such as culverts, do not have to allow for fish passage (because they have wrongly concluded that no fish are present). The mapping and typing mistakes then become a self-fulfilling reality. Our research has found that more than 70 percent of all culverts currently block or impede upstream migration of anadromous [returning to breed in fresh water] and resident fish. As a result, thousands of miles of potential fish habitat are lost because the fish cannot physically get there.
Every road that crosses a stream needs a culvert (or bridge) to allow water to pass under the road, whether it be a major highway or a logging road high in the watershed. Likewise for every railroad that crosses a stream, including those railroads used in the past for timber harvest operations. Every drainage ditch needs a culvert to pass water under the road. Every irrigation system and water diversion system in agricultural lands also need culverts to pass water.
Culverts Impede Fish Passage
How many culverts are there in Washington? No one knows for sure, but the number can be counted in the hundreds of thousands and perhaps over a million. Washington State Department of Transportation estimates there are 350 blocking culverts within their jurisdiction. Washington Department of Fish and Wildlife estimated there were approximately 2,400 blocking culverts that prevented anadromous access to over 3,000 miles of salmon habitat statewide. King County Surface Water Management estimates that 45-50 percent of culverts in non-forested King County are an impediment to fish migration, demonstrating that the problem is not restricted to forest lands.
It might be argued that any culvert that limits fish migration contributes to a decline in water quality due to deprivation of that stream reach of marine-derived nutrients. It is now recognized that marine-derived nutrients are essential for the productivity of our stream ecosystems. Marine-derived nutrients can only be delivered to our streams in the form of salmon and steelhead carcasses. These nutrients have been shown to have a direct effect upon the ability of a stream to produce healthy populations of juvenile fish and the insect populations upon which they depend. Culverts that limit fish distribution affect entire ecosystems by impacting upon the many and varied animal, bird and aquatic insect species that depend upon fish and fish carcasses for forage. This list is long and diverse, but includes such species as eagle, bear, raccoon, wren, dipper, raven, etc.
Culverts may also influence and contribute to a reduction in genetic diversity in our fish populations. Clearly, impassable culverts in areas of resident trout populations will restrict the breeding population to those fish that are present in a given stream reach. No further genetic input is possible within the reach from populations downstream. Since headwater cutthroat populations tend to be small and widely spaced, this can lead to inbreeding depression. It can render the population more likely to face extinction because of the limited diversity within the population.
In the anadromous zone, culverts that create impediments to fish passage may select for fish that are larger, in the case of velocity or perch barriers, or for fish that are smaller, in the case of depth barriers. Flow regimens may only allow passage within a narrow time window and therefore select for return time. These factors all contribute to a decrease in genetic diversity within the populations in a given stream, thereby reducing overall fitness of the population and reducing the effective breeding population in the stream reach.
Culverts That Allow Fish Passage
Here is a list of basic considerations that need to be addressed when designing, installing and maintaining the culvert:
1. Fish need to have adequate access to the pipe.
2. The outlet of the culvert needs to be low enough to permit fish to enter the pipe.
3. There may be a cumulative effect of culverts upon the energy reserves of fish that can limit the extent of upstream migration.
4. The water velocity within the pipe should not exceed the swimming capability of the fish.
5. The culvert should have sufficient water depth to permit the fish to swim through the pipe.
6. The culvert should be free of blocking debris within the pipe.
7. There should be adequate egress conditions at the upstream end of the pipe.
8. The culvert conditions listed above must be appropriate for the species and life history stage and physical condition of the fish in the stream.
9. The culvert should be designed to permit migration under the mean flows expected during the migration periods for all of the fish species and life history stages present in the stream.
This article was compiled by Helen Brandt, Ph.D. from technical reports by Stephen C. Conroy, Ph.D.
When this article was written Stephen C. Conroy, Ph.D., was the science and research director of Washington Trout.