Friday, March 8, 2024

Sediment from Klamath River Basin logging roads dwarfs sediment from dam removal

by Felice Pace

Lately there has been lots of media reporting, comments and commentary about the amount of sediment being released from PacifiCorp's Klamath River dams in preparation for dam decommissioning and removal. Concerns have been expressed about how that sediment may be impacting the River's ecosystems and fisheries. Below I  show that the amount of sediment being released from the dams is dwarfed by the amount of sediment released during major storms from the Basin's thousands of miles of unpaved and poorly maintained logging roads.

The amount of sediment to be released from PacifiCorp's dams has been estimated at 5 to 7 million cubic yards. That sounds like a lot of sediment. Consider, however, that, according to a Forest Service research report, during the 1996-97 New Year storm event an estimated 1.3 million tons of sediment was released from the approximate 8,000 miles of unpaved logging roads on the Klamath National Forest alone.

One of multiple road failures with sediment delivery to streams that 
occurred  on KNF logging roads during the New Year 2016 storm event.

The Klamath National Forest (KNF) is one of five national forests that are located within the Klamath River Basin. The KNF comprises an estimated 15% to 20% of the total Basin area. From this I calculate that a major storm event is likely to release 6.5 million tons of sediment to the Klamath River, that is, about the same amount of sediment that is being released from the dams in preparation for decommissioning.

Let that sink in. The sediment impact to the Klamath River from dam decommissioning is likely to be about the same as the sediment impact delivered to streams and thence to the Klamath River during any major storm event. To get a better understanding of the sediment impact from forest roads see the Forest Service research report at this link

Road blowout sediment deposited onto National Forest 
Road 46N64 in the Walker Creek Watershed near Seiad Valley

Of course it happens that the release of dam sediment is occurring during the rainy season and during a storm event. But I expect that high and flood flows will easily flush most of the fine sediment to the ocean in a short amount of time. Most of the juvenile salmon and steelhead are still in the tributary streams where they were born. As a result, Klamath fisheries will not be significantly impacted by the sediment released from PacifiCorp's dams.

Those who claim otherwise are the same people who have always fought dam removal. They have a axe to grind and are projecting impacts that are not now occurring and are unlikely to occur in the future. 

Forest roads are a problem

While concerns about the sediment impacts of dam removal are unfounded, the Klamath River and significant tributaries like the Scott River are sediment impaired. Recovery of Klamath River basin aquatic ecosystems and fisheries depends on removing those sediment impairments. The only way to do that is by addressing the #1 source of the sediment, that is, unpaved logging roads.