Final Answer:
Between 2008 and 2012, Tahoma Creek's longitudinal profile exhibited bed elevation changes of +2 meters at 4000m and -1.5 meters at 5250m below the South Tahoma Glacier. The +2m elevation at 4000m indicates sediment deposition, while the -1.5m at 5250m suggests erosion, showcasing the dynamic recovery from earlier debris flows.
Step-by-step explanation:
Between 2008 and 2012, Tahoma Creek underwent significant longitudinal profile changes indicative of recovery from earlier debris flows. At 4000m below the South Tahoma Glacier, the channel bed elevation increased by +2 meters. This positive change suggests sediment deposition, a crucial aspect of post-debris flow recovery. Debris flows typically bring a substantial amount of sediment, and the rise in bed elevation at this point signifies the accumulation of such material. This sedimentation process aids in rebuilding the channel bed and stabilizing the streambed after the disruptive debris flows.
Conversely, at 5250m below the glacier, the channel bed elevation decreased by -1.5 meters during the same period. This negative change implies erosion and the removal of sediment. It reflects the downstream transport of debris and sediment, showcasing the dynamic nature of recovery. The decrease in bed elevation suggests that the channel is actively adjusting and redistributing the material deposited during the debris flows.
This erosion process is crucial for stream channel morphology, as it helps restore the natural balance by transporting excess sediment downstream and facilitating the channel's resilience against future debris flows.