The Army Corps of Engineers' Short-Term Response to the Eruption of Mount St. Helens

Willingham, William F., Oregon Historical Quarterly

AT 8:32 ON THE MORNING of MAY 18, 1980, an earthquake of magnitude 5 on the Richter scale precipitated a massive landslide on Mount St. Helens's outwardly bulging north flank. The collapse of roughly 12 percent of the mountain, the largest landslide ever recorded, exposed gas-charged magma that had risen within the volcano. Instantaneously, billions of gallons of superheated groundwater, trapped inside the mountain, flashed into steam. Scientists later estimated the explosion at 24 megatons of energy--a blast five hundred times more powerful than the 20-kiloton atomic bomb that destroyed Hiroshima. The explosion ripped more than 1,200 feet off the top and center of Mount St. Helens, forming a huge crater over a mile in diameter. The onrushing avalanche debris displaced the water in Spirit Lake and raised the lake bed by 200 feet. Debris from the eruption covered 23 square miles of the North Fork Toutle River Valley to a depth of 150 feet. (1)

Approximately 3 billion cubic yards of material spewed out of the mountain. Some of the ejected material consisted of volcanic ash, which ascended 14 miles into the atmosphere over a 9-hour period. Other matter comprised mud and pyroclastic flows or surges that sped down the mountain at 100 miles an hour, pushing into the upper reaches of the North Fork and South Fork Toutle River drainages. These flows (averaging from 33 to 66 feet in depth) contained massive amounts of debris, rock, trees, water, and glacial ices in superheated condition. As the flows raced downstream, they filled in and leveled out the river beds, reducing channel capacity in the Cowlitz from 70,000 to 13,000 cubic feet per second (cfs). The mudflow deposited as much as 15 feet of sand, volcanic ash, and pumice in the river channels and 10 feet on the floodplain. The mudflow into the Columbia reduced the 40-foot-deep ship channel to 15 feet. The debris avalanche also created lakes in the Toutle River drainage, blocking them with eroded, unstable material. As these lakes retained rainwater or snowmelt, the danger of breaching and downstream flooding increased. Flying over the devastated area shortly after the eruption, President Jimmy Carter mused, "I've never seen anything like it.... The moon looks like a golf course compared to what's up there." (2)

A deep-draft vessel was grounded in the Columbia River ship channel off the mouth of the Cowlitz River, and thirty-one other vessels were trapped in the Portland and Kalama harbors. Another fifty ships enroute to the area had to stand off or be diverted to other West Coast ports. It was a navigation emergency and a potential economic disaster for the ports, communities, and industries that depended on the ship channel. The lower Cowlitz drainage faced a flood-control problem from the mudflows. For 21 miles of the Cowlitz River, downstream from the Toutle to the Columbia, infill had eliminated natural channel capacities. Forty-five thousand people had been left without flood protection. (3)

The eruption was a major natural disaster. Fifty-seven people were killed and 150 square miles of valuable forest were turned into wasteland. The avalanche of mud and debris sent into the Toutle, Cowlitz, and Columbia rivers disrupted navigation on the Columbia and threatened to cause long-term navigation and flooding problems. The U.S. Army Corps of Engineers, the federal agency immediately responsible for dealing with the disaster, faced a difficult and uncertain situation. Could the Corps, a government agency that was considered highly bureaucratic and technically conservative in its engineering philosophy, respond with appropriate technical solutions to the immediate and long-term water problems caused by this unprecedented natural disaster?

The Corps' responsibility for responding to the Mount St. Helens emergency stemmed from its congressionally authorized mission. Since 1824, the Corps had been charged with improving the nation's rivers and harbors for navigation. In the twentieth century, the Corps also became responsible for flood control, the development of multiple-purpose water resources development projects on the nation's major waterways, and regulatory responsibilities under the Clean Water Act of 1972. Over time, the Corps amassed considerable expertise in the planning, construction, operation, and maintenance of water resources projects across the nation.

Although the Corps of Engineers' organizational structure appeared heavily bureaucratic--at that time the Corps consisted of thirty-seven districts and eleven divisions reporting to headquarters in Washington, D.C.--appeared heavily bureaucratic, it was in practice a fairly decentralized outfit. While the division and higher headquarters exercised technical review and oversight of the districts to ensure consistency and compliance with laws and regulations, each district had a large measure of independence in carrying out the agency's water resources projects at the local level. This institutional flexibility and decentralized empowerment would prove essential in the Corps' short-term response to the Mount St. Helens disaster.

Immediately after the eruption, the Corps initiated emergency dredging to restore the shipping channel in the Columbia River and then devised and implemented both short- and long-term solutions to the flooding and navigation problems caused by continuing flows of volcanic material. In the immediate aftermath of the eruption, Corps staff implemented their response in the context of an anxious public and a skeptical political atmosphere in Washington, D.C. As the Corps developed its plans, the agency found itself caught between the fiscally frugal Reagan Administration, which was determined to hold down costs, and local interests that wanted complete flood protection as soon as possible and had little regard for the price tag. The Corps' short-term initiatives laid the groundwork for the cost-effective and technically sound engineering solutions that the agency ultimately developed to address long-term problems caused by the Mount St. Helens debris flow.

The Natural Setting

Prior to 1980, few people thought that a beautiful mountain in the Cascade Range contained the potential to cause devastating flooding in the Cowlitz drainage. Scientists considered Mount St. Helens and six other peaks in the Cascade Range as active volcanoes, each having erupted at least once during historical time. Because of its relative youth and explosive history, some volcanologists thought Mount St. Helens the most likely of the Cascade volcanoes to erupt in the near future. Planning for an event whose timing was impossible to accurately predict proved especially difficult, and geologists feared that the relative quiet of the Cascade volcanoes had lulled the public into a potentially dangerous disregard of volcanic hazards. (4)

Beginning in March 1980, frequent earthquakes, accompanied by minor steam and ash ejections, shook the mountain and announced a new phase in the geologic history of the volcano. No one, however, could be sure what to expect. As Dan Crandell, a leading geologist, observed at the time, "Mount St. Helens has done so many different things in the past that hardly anything would be a surprise. The only thing it hasn't done is blow itself apart." (5)

The eruption on May 18 was only the most recent event in 40,000 years of volcanic activity at Mount St. Helens. Typically, heavy winter rainfall accompanied by rapid snowmelt at the higher elevations of the Cascade Mountains can quickly convert the Cowlitz and its tributaries into torrents during the rainy season, from November to May. From the earliest days of white settlement, the Cowlitz River had offered both economic promise and potential ruin. The river provided rich bottomlands for farming and a means of transporting their produce to market but also posed a periodic danger from flooding. But the flooding that raged on the Cowlitz and Toutle rivers in the aftermath of the May 1980 eruption was an especially devastating form of that regularly encountered event.

Between the 1870s and 1920s, the Corps of Engineers, through its Portland District, had carried out channel improvement projects on the Cowlitz River to support navigation by shallow draft steamers. Each year, they removed hundreds of snags and other debris and occasionally built wing dams and bank revetments. In 1904, Congress authorized Corps dredging on the Cowlitz in combination with the other channel improvements. By the 1920s, however, navigation on the Cowlitz began to decline as railroads and highways provided more convenient alternatives to river traffic. The Corps did less and less work on the river. (6)

As the use of the Cowlitz River changed, local people's …

Questia, a part of Gale, Cengage Learning. www.questia.com
Publication information: Article title: The Army Corps of Engineers' Short-Term Response to the Eruption of Mount St. Helens. Contributors: Willingham, William F. - Author. Journal title: Oregon Historical Quarterly. Volume: 106. Issue: 2 Publication date: Summer 2005. Page number: 174. © 2009 Oregon Historical Society. COPYRIGHT 2005 Gale Group.

This material is protected by copyright and, with the exception of fair use, may not be further copied, distributed or transmitted in any form or by any means.