Let me begin with the obligatory caveat: it is impossible to relate any specific weather event to global warming.
Then, let me add some statements from the recent 4th IPCC report on extreme weather events:
Observed changes “At continental, regional, and ocean basin scales, numerous long-term changes in climate have been observed. These include changes in Arctic temperatures and ice, widespread changes in precipitation amounts, ocean salinity, wind patterns and aspects of extreme weather including droughts, heavy precipitation, heat waves and the intensity of tropical cyclones.”
“More intense and longer droughts have been observed over wider areas since the 1970s, particularly in the tropics and subtropics. Increased drying linked with higher temperatures and decreased precipitation have contributed to changes in drought. Changes in sea surface temperatures (SST), wind patterns, and decreased snowpack and snow cover have also been linked to droughts.”
“The frequency of heavy precipitation events has increased over most land areas, consistent with warming and observed increases of atmospheric water vapour.”
Projections of future changes
“It is very likely that hot extremes, heat waves, and heavy precipitation events will continue to become more frequent.” (In IPCC terminology, “very likely” means a probability greater than 90 percent and “likely” means a probability greater than 66 percent.)
“Extra-tropical storm tracks are projected to move poleward, with consequent changes in wind, precipitation, and temperature patterns, continuing the broad pattern of observed trends over the last half-century.”
“Since the [2001 IPCC report] there is an improving understanding of projected patterns of precipitation. Increases in the amount of precipitation are very likely in high-latitudes, while decreases are likely in most subtropical land regions…continuing observed patterns in recent trends.”
“There is now higher confidence in projected patterns of warming and other regional-scale features, including changes in wind patterns, precipitation, and some aspects of extremes and of ice.”[all emphases–JR]
Interstate 5 Lewis County Flooding December 5, 2007
Now, lets talk about what has happened in Washington State last winter and this winter. In December 2007 and January 2009 Washington received extremely high levels of rainfall leading to heavy flooding that caused hundreds of millions of dollars of damage and the closure of Interstate 5 between Seattle and Portland. This year, several rivers in Western Washington have reached flood levels never seen before.
Additionally, this year, the rainfall and flooding was preceded by heavy snowfall so that once the temperatures rose and the rains came, all the mountain passes that divide Eastern from Western Washington were closed because of avalanches or the danger of avalanches. Moreover, the melting of the recent snow means that come summer we will derive no benefit from December’s heavy snowfall, because our current warm temperatures and the flooding will have swept away much of the snow pack, which, prior to the heavy December snows, was well below normal.
According to the University of Washington’s Climate Impacts Group:
Examined over the past 30 days and the period since 1 October (the beginning of the Water Year), conditions have been drier and slightly warmer than normal (precipitation, temperature). The snow pack, as measured in terms of snow water equivalent, is less than 50% of normal for this point of the season throughout the Columbia Basin (18 December analysis, map legend, current analysis, NWRFC).
Experts generally agree that the worst flooding, that in Lewis County, home to the second largest floodplain in the state, was made much destructive by county policies favoring commercial development on the flood plain itself. Many businesses, including a large Walmart have been constructed just off of Interstate 5 which in Lewis County bisects the flood plane. The local county council has not only approved but pushed such development in order to provide an economic boost to a region that has been hard hit by the decline in timber revenues. (Lewis County is one of the reddest places in blue Western Washington and it’s elected officials are well known for their disregard, if not contempt, for scientific research and opinion.)
Additionally, lax oversight by the state’s Department of Natural Resources, whose director was thrown out by the voters in the recent election in no small part because of concerns about his handling of the permitting and supervision of clearcutting by Weyerhaeuser and other smaller companies in the area, contributed to the damage caused by last year’s and, presumably, this years floods. Slopes that had been clearcut in violation of state rules washed away under the heavy rains, sweeping tons of top soil, rocks and trees stumps into local creeks and rivers, which then backed up until these accidental dams brook releasing all the pent up water and debris in a mad rush. The fact that, because of the development, much of the floodplain had been paved over for building sites and parking lots did not help.
An investigation by the Seattle Post-Intelligencer after last year’s flooding had the following to say about why the flooding caused so much damage:
Big-box stores, restaurants and strip malls galore. A railroad line extension, parking lots for a church. A coal-unloading facility, a new natural-gas pipeline, a mine expansion. And barns, homes, carports and shops. All built in the floodplain.
Then last Monday, heavy rain punched into the watershed from the southwest. Faster than anyone had ever seen before, torrents of water gouged hillsides, broke levees and overtopped dikes as flood gauges reached record highs and some blew out altogether. At the worst of it, some 10 feet of water covered parts of Chehalis, and hundreds of people watched their homes and belongings go under. One man was swept away in the deluge.
Now as the water recedes and residents of Lewis County take stock, many are looking back in time, wondering how much the legacy of development in the floodplain, and clear-cut logging in the upriver drainages, contributed to their woes.
Many state officials and regional experts, including a former county manager who says he was fired after criticizing floodplain development, say they have been warning for years that the hunger for development was running counter to common sense.
They note that while many counties, including neighboring Thurston, have either banned or seriously crimped development in the floodplain, Lewis County has not.
“It’s kind of sad, we keep repeating the same mistakes, even when we know better,” said Andy McMillan, a longtime wetlands manager for the state Department of Ecology. “It’s the same old things coming into play: There’s money to be made, and people want to make the most money for their land.”
But in the wake of the storm, Lewis County leaders still say it’s unfair to blame them for nature’s wrath. And they predict the development will go on.
“The floodplain in the Chehalis is so vast that the filling in the floodplain for local development has no significant impact,” said Bob Nacht, the director of community development for the city of Chehalis.
The investigation also focused on the clearcutting:
Clear-cuts increase risk
All the while Lewis County has debated its floodplain development, logging has been chewing through the forests in the Chehalis watershed since the last flood.
Logging has declined overall in Western Washington in the past 15 years. But the most intensive cutting is still happening on the type of industrial forestlands that dominate the Chehalis watershed.
Since 2002 alone, about 230,972 acres of the watershed — up to 14 percent of the forestland there — have been logged, according to the state Department of Natural Resources.
It’s only about 2.3 percent of the watershed a year. But the effects of clear-cuts and logging roads stick around for years, potential ticking time bombs for large landslides, said Gordon Grant, a hydrologist for the federal Forest Service’s Pacific Northwest Research Station in Corvallis, Ore. Landslides can happen anywhere, including on forested ground. But forestland that has been clear-cut is up to five times more likely to slide in flood conditions, and forestland with logging roads is even more vulnerable, Grant said. Those landslides can bring down logs, creating debris flows that stop up streams, culverts and even rivers.
That means even more flooding when the big rains finally come.
Last week, they did.
In yesterday’s Post Intelligencer, the newspaper reported on a federal study that bolsters the conclusions that it’s reporters drew from last year’s flooding. (Kudos to the PI for actually mentioning climate change in the context of a story about the weather.)
Logging and development are prime suspects because dense forests intercept and slow down rainfall before it becomes a flood, while development plasters concrete and asphalt across marshy areas that once soaked up floodwaters. Meanwhile, climate change appears to be increasing the incidence of extraordinarily heavy rainstorms, scientists say.
A federal study adds credence to the development and logging hypotheses. In fact, the Puget Sound region so far has come out No. 1 nationally in an examination of how land cover changed — primarily from development and clearcutting — from 1973 to 2000.
The study is nearly finished, and so far no faster rate of land conversion has been found anywhere in the nation, said Dan Sorenson, a U.S. Geological Survey geographer.
The main reason is clearcutting, which decreased forest cover by 10 percent. The No. 2 reason is the footprint of development, which increased nearly 7 percent.
Some of that development is going into floodplains — the areas surrounding riverbanks where rivers traditionally spilled over after winter storms. Virtually all the land between West Seattle and Beacon Hill, for example, once was covered by the then-multichanneled Duwamish River and associated marshes.
None of this week’s damage should surprise anyone. In fact, one year ago this week, University of Washington geologist David Montgomery warned state legislators in testimony: “It appears to me that the flooding and landslide problems (from) this December storm stem from the combination of an unusually large storm and decades of risky behavior both in upland forestry practices and downstream floodplain development.
“The combination put people at risk and will do so again under the present system.”
Video from the December 2007 flooding in Lewis County. Note that the sound track is Paul Simon and Phoebe Snow singing “I’ve had a long streak of bad luck but I pray it’s gone at last” (Actually, you won’t be able to hear the audio, because You Tube has just disabled it for copyright reasons, but you can read the lyrics here)
Well, unfortunately, it isn’t. Here’s video from a couple of days ago showing the most recent flooding in Lewis County:
And here’s another short one from a different part of the county:
The Lewis county flooding brings up one of the basic issues of Climaticide: how much of the blame for such disasters do we attribute to human folly (global warming, which as this point can no longer be seen as an historical accident but rather can only be attributed to greed, ignorance and stupidity) and how much do we lay at the feet of human folly (development in floodplains and watersheds, clearcutting–things that are stupid in any case, but which are doubly so in the light of the IPCC’s prediction of increased extreme weather events, prominently among which figures increased precipitation delivered in more intense episodes)?
Let’s conclude this piece with a quotation from a resident of Lewis County regarding last year’s flooding.
All sides agree that the rain itself was stunning, with 15 inches falling on parts of the Chehalis River basin.
“Who do you blame for that?” said Bobbi Fenn, 54, who said she had lived in the area near Curtis for half a century and never before seen such flooding. “Sometimes things just happen. I’ve been thinking someone should write a book about it, but I wouldn’t want to read it.”