Winter 2006-07 Flooding
The NPS has issued a project proposal for public comment to "Install Interim Flood Protection Measures Along Mather Memorial Parkway (SR410)", see proposal, which states,
"The project area includes the White River and SR 410 between milepost 57.9 and milepost 60.0. Proposed activities include the installation of structures, such as buried log and rock toes, log debris walls, headcut log fills, and engineered log jams at strategic locations in the White River floodplain to provide flood protection for the road. The structures are constructed of logs and ballast rock engineered to act as a single unit."
You can download the documents from the NPS Web page. Like all glacial rivers, those draining the glaciers of Mt. Rainier have the same problems with the lower reaches, see general description and a more specific one for the White River and a USGS report on Puyallup, Carbon and White Rivers, see SIR 2010-5240.
In short, glacial rivers continually release sediment in the upper reaches below the glaciers to the downstream channel which aggrades the channel raising the bed and river level excerbating flooding along the river. Highway 410 (Mather Memorial Highway) was constructed years ago along the White River where it now is under threat from the flooding which has occurred in several recent years.
The NPS is engaging in the river stablization work to protect the highway from future flooding while longer term solutions are found for the highway out of the valley floor and the river channel.