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Flooded by Greed

by Dave McBee

I began noticing a curious thing while watching local weather reports on Seattle TV news: during the wet season (October through April, usually) when the rains were at their worst and flood warnings were being posted, the Skokomish River was consistently the first to reach flood stage, and stayed at flood stage the longest. Reporters would talk vaguely of "fifty-year floods", and "hundred-year floods", and some grizzled local resident of the sandbagged Skokomish Valley would be heard to exasperate, "It never used to flood like this...."

The Skokomish is not that big a river (7th largest entering Puget Sound in terms of discharge rate; 8th in drainage area), and there are two dams on the North Fork. So why does it flood so often, and so easily? And is it really flooding more than it used to?

Maybe it rains there a lot, folks in Seattle assume, and it does, but there's more to it than just rain. Take a good look at any reasonably detailed Washington atlas: there are so many thin red lines (signifying logging roads) along the Skokomish that it looks like a bloodshot eye. But as I looked further, I found that there was even more to it that just heavy logging and lots of rain.

Skokomish Country

The Skokomish River drains about 240 square miles at the southeast corner of the Olympic Mountains, emptying into Hood Canal. The drainage basin is steep, flowing off Olympic peaks of 5000 to 6000 feet and rapidly reaching sea level. Rainfall is high, with annual precipitation ranging from 200 to 220 inches on the Olympic crest in the upper watershed, to 80 to 90 inches in the Skokomish Valley, and 75 to 80 inches at the river's mouth. Average precipitation for the basin as a whole is about 133 inches per year. Seattle, for comparison, receives about 36 inches per year.

The Skokomish's upper basin contains two sub-basins, the 118 square mile North Fork, and the 104 square mile South Fork. Vance Creek, drainage about 25 square miles, is a tributary of the South Fork.

On the North Fork, two dams below Lake Cushman divert 90% of the North Fork's flow from the basin to a hydroelectric power plant on Hood Canal. Above Lake Cushman, the Upper North Fork drainage is almost entirely within Olympic National Park, and is heavily forested in mature and old growth stages.

The South Fork sub-basin is largely undeveloped, but has been subjected to extensive clearcut logging.

Below the confluence of the two forks, the mainstream Skokomish flows through a wide, flat valley for its last nine miles. This is where the flooding takes place.

Who owns it?

About half the Skokomish basin lies within the Olympic National Forest; another eighteen percent is in the National Park. The City of Tacoma owns six percent (10,000 acres) around Lake Cushman and the dams, which provide power for the city. The State of Washington owns three percent, and the Skokomish Indian Tribe owns two percent at the river's mouth, the Tribe's reservation. The remaining 23 percent is privately owned, largely by the Simpson Timber Company.

Simpson has long been present in the area: they own outright 250,000 acres in the Skokomish, Satsop, and Wynoochee drainages outside of the Olympic National Forest. In 1947, the Simpson Company signed a 100-year agreement with the U.S. Forest Service to harvest timber in the Olympic National Forest, ostensibly to provide economic stability to the communities of the area, as the lumber would have to be manufactured (turned into two-by-fours and whatnot) in the nearby communities of Shelton, McCleary, and Elma. The agreement enabled Simpson to clearcut, in the Skokomish South Fork basin alone (called, interestingly, the Cooperative Sustained Yield Unit):

The South Fork basin within the Shelton CSYU now appears to be about 80 percent clearcut (based on visual estimates obtained during overflights). That, over a hundred year period, is about as sustainable as a heart attack.

From the early 1970's until 1984 clearcutting in Olympic National Forest went on at a feverish pace, at times literally night and day. It is as if the Simpson people saw the writing on the wall (see Endangered Species Act, signed into law in 1973) and decided to grab while they could. The Simpson Timber Company opted out of their contract in 1984; the minimal acreage cut after that date reflects completion of contractual work.

The soils of the Skokomish basin have high potential for erosion due to slope steepness and heavy rainfall, and are easily disturbed by clearcut logging and roadbuilding. There are 354 miles of roads on National Forest land within the Skokomish basin. According to the Forest Service's Watershed Analysis, surface erosion within the Skokomish watershed is primarily the result of 'side cast' road construction techniques. The analysis identified 2500 erosion sites in the basin, 95 percent of which are located adjacent to roads. The analysis concludes that "significant acres of upland terrestrial habitat have been altered or degraded as a result of road construction, timber harvest techniques, and fire management activities."

Can you say evapotranspiration?

Vegetation intercepts, stores, and slowly releases water in the form of vapor. This gradual release of moisture protects the local environment from erosion, degradation of the landscape, and flooding.

When the forest is removed, erosion rates accelerate, in the form of gullying (a surface effect involving the movement of sediment by running water), and by mass wasting (in unstable conditions, soil and rock are pulled downhill by gravity). So it goes.

O.K., one more big word, than I'll back off! So this sediment-laden water roils downstream, and somewhere downriver where the gradient decreases, sediment starts to drop out, raising the river's bed. This is called aggradation. A river's delta is created in this way. But something has happened to the Skokomish to alter normal aggradation patterns.

Flush early. Flush often...

Since 1926 the Lake Cushman Hydroelectric Project has impounded 90 percent of the flow of the North Fork Skokomish behind two dams, then diverted it out of the watershed directly to its power plant along Hood Canal. This has had both a positive and a negative effect on flooding along the mainstem Skokomish.

The dams store floodwaters, reducing peak discharges from the North Fork that would otherwise cause damage. Prior to the Project, the North Fork produced 45 percent of the total mainstem Skokomish flow. But at the same time that reduction in flow reduces the mainstem's ability to carry sediment, resulting in unnatural aggradation.

In other words, all that dirt-choked water runs down the clearcut South Fork, hits the low-gradient mainstem and, without the flushing effect of the North Fork's flow, drops its load of sediment right there.

Channel cross-sections upstream of US 101 show a two to three foot rise in riverbed elevation between 1969 and 1992. This increase in riverbed elevation reduces available flow area, thus, flooding can occur at lower water levels. The high rate of aggradation has been identified as a root cause of progressively more severe flooding on the Skokomish.

And with the sediment dropping out before it reaches the river's delta, the delta itself no longer receives its historical volume of sediment. The sediments that do reach the delta are deposited higher, and with normal erosion continuing at the delta's outer edge, the result is a steepening of the delta slope. This reduces the delta's biological productivity, and negatively affects native salmon runs by affecting salinity.

The Skokomish Indian Tribe, with its reservation at the river's mouth, noticed the reduction in the river's productivity early on, and started a lawsuit against the Olympic National Forest in 1982. The suit was not carried to completion because the Tribe lacked the funds needed to continue.

The embankment supporting US 101 where it crosses the Skokomish five miles from its mouth, as well as the embankment supporting State Route 106 where it crosses the Skokomish two miles from its mouth, both contribute to high rates of aggradation. A number of dikes along the mainstem Skokomish simply force floodwaters to areas where there are no dikes.

What can be salvaged, and how?

Options for treating the symptom (flooding) include

• dredging the deposits out of the riverbed along with managed flushing flows from the North Fork,
• mainstem widening,
• side-channel clearing,
• changing the amount of water released from Lake Cushman into the North Fork,
• modifying the embankments and bridges for Routes 101 and 106 to locally reduce flood depths and associated damages,
• and bringing existing dikes into compliance, or removing them.

To treat the causes further upstream, the United States Forest Service Watershed Analysis has recommended evaluation of their own road management objectives, and finding ways to reduce sediment loss on high-sediment roads. It has also recommended less severe logging techniques, such as delayed thinning and smaller harvest units combined with longer periods between harvests, and the reduction of roadbuilding. They are already performing watershed restoration projects such as road decommissioning and the bioengineering of eroding slopes. Why cut any more on National Forest land, and why build any more roads?

The Mason County Skokomish River Comprehensive Flood Hazard Management Plan, whose documents I have used heavily in writing this article, has also recommended that the Simpson Timber Company complete a watershed analysis for lands it owns outside the National Forest, and that Simpson keep Skokomish Valley residents informed as to their progress with their Road Maintenance, Rehabilitation, and Abandonment Plan. It may be akin to locking the barn door after all the cows have been spotted bobbing, udders up, downriver, but it's a start.

There will be more flooding on the Skokomish, and it will get worse. The flooding along the Skokomish river is a disaster that was years in the making. The hydroelectric project on the North Fork was looked upon as a great benefit, a way to prevent flooding, not to make the flooding worse. And the pact with Simpson may have created a lot of jobs for a time.

It's too late to place blame. No it's not: Simpson deserves a real big poop-filled flaming paper sack on their porch every night forever. And take away their shoes. It's a shame that federal funds in the form of grants will be used to fix the problem... if it can be fixed.

Dave McBee tries hard not to get his feet wet but on the Skokomish, this isn't easy.