Amtrak travel continues to increase here, and passenger-rail advocates are pressing to add a third round-trip between Seattle and Vancouver. indeed, the Washington State Department of Transportation’s long-range plan calls for four such round-trips. But the increasingly familiar winter ritual of shunting passengers into hastily chartered substitute buses — or of sometimes even leaving passengers with no alternative transportation — will do nothing for the ridership growth that ultimately underpins the case for increasing service in the corridor.
For rail passengers, landslide season opened over Thanksgiving with a 48-hour closure of Amtrak Cascades services because of a slide near Everett after several days of heavy rain. Déjà vu all over again.
After two years in a row of particularly severe troubles, officials will study the technical aspects of the problem, and they are looking for whatever solutions might be possible. But the forces of nature will not easily be restrained.
This December, a month opening with little rainfall, has not brought any new closures but the trend over the past two years has been a sharp increase in Amtrak disruptions because of landslides between Seattle and Vancouver. The test usually comes in the first quarter of the year, January through March, according to statistics from the Washington State Department of Transportation (WSDOT).
The primary area for the disruptions is the 34 miles of track that hugs the Puget Sound shoreline between Everett and Seattle, where Sound Transit's Sounder service also operates and faces the same disruptions as Amtrak. But the slopes are also prone to slippage at many other points, including, notably, White Rock, B.C.
According to WSDOT’s data, the number of days when services were disrupted in the year’s first quarter climbed from four in 2009 to 10 in 2010 and finally to 33 — every third day of the time period — in 2011. That’s an increase of 725 percent in two years. The data reflect incidents all along the corridor in Washington state, including points south of Seattle.
What’s going on here? The region may have just faced two rainy years in a row, but if 2012 somehow mimicked the tripling that occurred in 2011, Amtrak service might as well take a three months’ winter vacation.
Any time a slide hits the rails, the Burlington Northern Santa Fe Railway (BNSF), which owns the tracks, shuts passenger service down, and keeps it shut down for 48 hours. It’s a company policy, not a federal rule, and it’s been in operation for about ten years, BNSF spokesman Gus Melonas told Crosscut last March. BNSF generally allows its freight trains to resume travel as soon as crews remove the debris.
It’s a matter of safety for passengers, and of legal liability for the huge railroad, and slides are certainly not a casual matter. On Jan. 15, 1997, a huge mudflow knocked five cars of a BNSF freight train into Puget Sound near Woodway in Snohomish County, two hours after an Amtrak train and its passengers had passed through. Passenger service had been suspended from Dec. 27 to Jan. 12 because of landslides launched by heavy rains.
Downpours are certainly not new in the region; nor are landslides. The closures of last winter have precedents in 2006 as well as 1997, according to news accounts and climate data. WSDOT has no landslide statistics from before 2009, so extensive comparisons are not possible. An examination of WSDOT records and rainfall data from the University of Washington the past three winters shows a very strong correlation between rainfall (measured at Everett, near the primary landslide areas) and rail closures resulting from slides.
Of the 2011 first quarter’s 33 days of disruption, 29 came in January and March: February was a dry month. Close to half of January’s trains were idled because of landslides, although rainfall for the month barely exceeded the normal figure for the past 15 years. March’s cancellations were virtually equivalent to January’s, but the March rainfall was well above normal (6.1 inches vs. 3.6 inches historically).
University of Washington geologist David Montgomery, who studies landslides, told Crosscut that there are three main factors in slides like those along the Seattle-Vancouver corridor: 1) state of the land; and whether there are trees, vegetation and root systems to hold the soil; 2) intensity or duration of rainfall; and 3) saturation; a good long soak weakens the soil for the next downpour.
All of those elements were involved in the winter of 1996-97, one of the worst in recent years. Rex Baum, who researched the 1997 landslide for the U.S. Geological Survey, recalled that the slide that pushed the rail cars into the Sound came a couple of weeks after the heaviest rainfall. He noted that the area has geologic conditions that lead to this sort of sliding: clay-type soils along the toe of a bluff, with fine sandy soil as a cover. When the soil becomes saturated and more rain hits, the sandy soil slides off the clay (to over-simplify a complex matter). Baum told us that these conditions haven't changed a great deal over time, and are not likely to change in the future.
Because the slide area is so large, structural fixes are not practical, leaving matters largely on the shoulders of property owners and local agencies. Education of landowners can make a difference, he added. The 1996-97 landslide season prompted a comprehensive study of Seattle-area sliding, sponsored by the City and USGS. "Contributing causes of landsliding may be myriad, but water is involved in nearly all of the cases," consulting geotechnical engineers Shannon & Wilson found. "Consistent with other studies in the City and the region, 84 percent of the reported landslides may have had some factor of human influence associated with them." Rainfall, saturated soils, and human activity are the major factors in sliding, with intervention possible only in the latter case; and then somewhat difficult.
In the two worst landslide periods in 2011 a deluge was swiftly followed by landslides. But accumulated rainfall is also important; although November and December are historically the months of heaviest rainfall over the past two decades (averaging 5.43 inches and 5.04 inches respectively), the worst landslides take place in the ensuing three months, when rainfall averages nearly 30 percent less. Rain falling on saturated soil causes more damage, although the volume of rainfall may be less.
Climate scientists predict wetter winters in the region because of global warming and periodic ocean-influenced weather patterns. State climatologist Nick Bond notes on his website that “odds exceed 50% for chances of above normal precipitation for the entire state” for the 2011-2012 season, with even higher odds in Western Washington — thanks to a La Niña weather pattern.
In the longer term, the Climate Impacts Group at the University of Washington foresees relatively modest but important changes in rainfall because of global warming: “Projected changes in annual precipitation, averaged over all models, are small (+1 to +2%), but some models project an enhanced seasonal cycle with changes toward wetter autumns and winters and drier summers.” Wetter winters pose obvious problems for coastal landslide areas.
In the narrowly constricted rail corridor between Seattle and Vancouver, increasing and competing uses, as well as — according to these scientists — wetter weather are thus on collision tracks. Rail operators and public agencies have limited capability to address the challenge.
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