The motivation for this work is how to best manage increasing flood risk given sedimentation in rivers with limited management options (because dredging is not an effective long-term solution, it is expensive, and potentially damaging to aquatic habitat and biota).Additionally the management of the system must cope with the prospect of increasing sediment production from the steep flanks of Mount Rainier and increasing sediment delivery by rivers to the lowlands.Sedimentation in rivers downstream of Mount Rainier in Washington State has exacerbated flooding.
Rapid mainstem widening, streambank erosion, braidplain development, and channel aggradation is a transient sediment storage signal morphodynamically prograding downstream through the Carbon, Nisqually, and other rivers, from glacier meltwater channels towards lower gradients that approach Mount Rainier National Park (MRNP) boundaries.
Coarse glaciogenic sediment is delivered to high-gradient (10%) headwater systems through high ratio sediment:water flows and is stored along intermediate channel corridors where gradients decrease towards deposition (~5-10%) and further at MRNP boundaries (~1-2%).
The upper Carbon R had been historically aggrading and widening until a full avulsion (ca.
Small-scale facies changes and the formation of individual bedforms are interpreted as controlled by fluctuating discharge, bed topography and pulsating unstable flows.
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co.