Regular readers of All Things Mount Rainier can be forgiven for feeling a sense of despair these last couple of months. The two previous columns focused on Mount Rainier’s retreating glaciers, which have shrunk dramatically in recent years, and the related processes of aggradation, flooding, and debris flows, all of which have increased in frequency during that time. That’s not very encouraging news! Fortunately, projects in the park and the neighboring watersheds are mitigating the effects of those challenges by protecting property and potentially saving lives. Today, we’ll dig into a few success stories that cope with floods and erosion, two events connected to retreating glaciers.
The first example is practically in our backyard: the Carbon River road. In the park’s early years, the Paradise area on the mountain’s south side was the main destination for visitors. Opened in 1912, the road attracted thousands of people each year, and park administrators soon became concerned about the impacts of heavy use at Paradise. Park supporters also wanted increased access to Mount Rainier’s many wonders, and these factors led to the decision to build a road into the park’s northwest corner. A road into the Carbon River area, people reasoned, would relieve the crowding at Paradise, provide a shorter drive from Seattle and Tacoma to the park, and the appeal of the Carbon’s mighty old growth forest and close-up views of the glacier would rival the attractions at Paradise.
Construction of the road began in 1921, and trouble soon followed. The road’s engineers used outdated wagon road technology to follow the path of least resistance and built squarely on the Carbon River floodplain. The road flooded and eroded before it was even completed, an omen of things to come.
Between 1933 and 1940, the Ipsut Creek Camp of the Civilian Conservation Corps (CCC) poured thousands of hours of labor into the road by installing log cribbing and rock gabions intended to stabilize the riverbank and keep the Carbon within its margins. But not even the CCC with their youthful work force and overconfident motto (“We can take it!”) could contain the Carbon; rockslides, flooding, and road damage continued until 1950, when the Park Service converted the last three miles of road into today’s trail.
Flooding and washouts occurred on a regular basis, including a 100-year flood in 1996 that caused half a million dollars of damage to the road and a picnic area. The final straw came in November 2006 with 18 inches of rain in 36 hours, and subsequent flooding damaged the road in six places that totaled over a linear mile. Engineered logjams (ELJs), already used to control erosion on the Nisqually and other waterways in Washington, seemed like the last chance to stabilize the riverbank and protect the road from further damage.
As a volunteer in July 2011, I watched a giant excavator install five ELJs near the Carbon River entrance. For each, the operator buried a handful of 30-foot logs vertically into the riverbed, leaving about 10 feet of each log exposed above ground. He then wedged root wads, smaller logs, and other debris between the uprights to build a structure intended to slow the water’s flow. This causes it to drop some of its sediment load, changes the riverbed’s grade, and gradually moves the river away from the bank.
I check on the ELJs every time I head up the Carbon, and 10 years in, they continue to hold steady with no further damage. The river is gradually moving away from the road, reducing the potential for further flood damage and erosion at this spot—a bona fide success story.
Besides engineered logjams, there are other ways for roads, property, and floodplains to coexist. Local governments in the Puyallup River basin snapped into action after 15 flood disasters in 50 years and in one strategy, Pierce County purchased nearly 2,000 acres of property and homes located on floodplains. The county then removed the structures and held the land vacant, breaking the cycle of recurring flood damage.
Another success story is the use of setback levees, large earthen and rock embankments that keep floodwaters away from homes and roadways. In the last 20 years, Pierce County and its partners have installed multiple levees along the Puyallup River. To check one out, drive through Orting and head out of town on Calistoga Street. As you approach the bridge crossing the river, you’ll find a ginormous, 1.5-mile long rock levee running parallel to the Puyallup. Winter floods once damaged property and closed roads on a regular basis, but not anymore. Known as the Calistoga Setback Levee, it contains the flow when the river exceeds its banks. Notice the wide margin of trees and shrubs between the river and the levee, 53 acres of reconnected ancestral floodplain. The Puyallup surges onto the floodplain during high water events, reducing the abrasive flows in the mainstream that destroy salmon redds and displace juvenile salmon. The inundated floodplain adds nutrients to the soils, provides food for the fish, and is an excellent off-channel habitat for migrating salmon—one of the best ways to restore the salmon runs. The Calistoga Levee was so successful in mitigating flood damage and creating habitat that the project has won multiple awards (yes, levees can win awards.)
Other flood prevention and floodplain restoration projects have sprung up in the lower Puyallup. King County led an $18 million project that reduced flood risk to over 200 homes in Sumner and Pacific that reconnected 121 acres of off-channel habitat to the nearby White River, which flows into the Puyallup at Sumner.
Another good news project is the recently completed South Prairie Creek Preserve on an old dairy farm on South Prairie Creek, the most important salmon-producing waterway in the Puyallup watershed. Partners including the Puyallup Tribe of Indians, South Puget Sound Salmon Enhancement Group, Pierce County, and the Pierce Conservation District chipped in to demolish the vacant buildings and emplace large woody debris in the creek, improving the habitat for salmon. They also installed native plants on 18 acres bordering the creek, providing much-needed shade (and thus cooler water temperatures) for migrating salmon.
While there’s still plenty to be concerned about regarding Mount Rainier, these stories are just a sampling of the good news that surrounds us. We’ll keep with that theme in next month’s column, when we’ll look at the return of rare and endangered species to the park, the restoration of the Paradise meadows, and other stories to feed the soul. In the meantime, keep your boots dry and your spirits high.