More than a century of change on the Sauk River—glacial retreat, logging in the watershed, and alterations downstream—is forcing the Sauk-Suiattle Tribe to move homes, administrative offices, and a longhouse farther upland and away from the river.
“The tribe currently has no defenses to stop the river from migrating into residential housing and tribal offices,” concludes a 64-page flood and erosion risk assessment by Natural Systems Design, a Seattle-based environmental planning firm. “Because of the warming climate, [river migration] is much more likely and poses an unacceptable level of risk to the Sauk-Suiattle Tribe over the next several decades. Severe and irretrievable damages, and possible loss of life, are an inevitable consequence of failing to move residents and facilities out of their current location.”
Jason Joseph, Sauk-Suiattle’s natural resources director, said the tribe has purchased 40 acres it wants to have placed into trust and is working with the Washington State Department of Natural Resources to gain access across a DNR easement. Then, the tribe will locate funding for installation of infrastructure and for construction.
The comprehensive report, Flood and Erosion Hazard Assessment for the Sauk-Suiattle Indian Tribe, is expected to help the tribe in its efforts.The study was supported by a federal Environmental Protection Agency grant made available through the Puget Sound Partnership and a partnership with the U.S. Geological Survey.
All told, 20 homes and five administrative buildings will be built at the new site. The longhouse—built between 1989 and 1999, and the first since eight Sauk-Suiattle longhouses were destroyed by settlers in the late 1800s—may be dismantled, moved and rebuilt, Joseph said.
The Sauk River’s headwaters start at glaciers at 10,500-foot elevation in the north Cascade mountain range. En route to its confluence with the Suiattle River, the Sauk River drains a watershed encompassing 314 square miles; the Suiattle drains a watershed area of 344 square miles. The merged rivers continue on to join the Skagit River, which flows to the Salish Sea.
Precipitation at Sauk-Suiattle averages 81 inches annually; with rain and snow on the higher elevations, the average is 125 inches annually over the entire watershed. The watershed is 75 percent forested.
Here are the issues, according to the assessment: One, 17 percent of the Sauk River watershed has been logged since the late 1800s. Two, glaciers—which are an important control on seasonal patterns of stream flow—have receded as much as 67 percent since 1890. Third, flood control measures downstream, such as dikes and rip rap, have sped the river’s flow and caused stream-bank erosion upstream.
The results: Between 1989 and 2013, the river channel migrated west at an average rate of 4.3 feet per year, according to the assessment. The homes, administrative offices and longhouse are currently located about 1,100 feet from the active channel of the river, separated by forested floodplain.
“Un-interrupted at this rate, the river would reach housing within 25 years,” the assessment states. “This could potentially happen much sooner.”
The assessment adds that within the next 80 years, the magnitude of flooding is expected to increase 50 percent and the frequency of flooding more than double.
“People have already seen things happen,” Robert Franklin, Sauk-Suiattle Tribe’s fisheries program manager at the time, told the Northwest Indian Fisheries Commission magazine in September 2012. “A bridge washed out on the Suiattle [River] in 2006. We had record floods in 2006 and 2009.”
Salmon habitat has been affected too. When a glacier recedes, slopes of sediment previously covered or buttressed by snow and ice are exposed to rainfall, increasing the amount of sediment that washes downstream.
Increases in sediment can lead to changes in riverbed elevation, fill pools and side channels used by salmon, and reduce overhanging cover that helps keep water cool. According to the assessment, the eggs of fall-spawning salmon could be threatened by faster, higher flows if snowfall no longer melts slowly and instead becomes rain that enters the river right away.
“As glaciers disappear and no longer contribute cold melt water in the summer, [river] temperatures will rise, getting too warm for fish and making it more difficult for them to survive and grow,” Franklin told magazine. Furthermore, he added, the assessment warns that should extensive clearcut logging occur again in the watershed, “it could aggravate peak runoff, reduce low flows and increase sediment inputs.”
Joseph said Sauk-Suiattle is considering several solutions, including planting trees and native plants that can stabilize banks and provide food and materials traditionally used by the Sauk-Suiattle people.
And, of course, moving to higher ground.
“Ideally, we would move the entire reservation,” Joseph said in an announcement about the study, released last year. “The results of this study will assist in that effort. However, we still have to maintain our tribal lands in the meantime.”