Disturbance Regime in Unglaciated Confined Channels

Picture of highway damage from Big Thompson Flood 1976

(Above and Below) Erosion in confined reaches of the Big Thompson River during the 1976 flash flood.

(Photo by S. Schumm)

Picture of highway destruction from Big Thompson Flood

Debris Flows - Unglaciated Confined Channels

Unglaciated regions of the Colorado Front Range lie below 2,300 m, which coincides with a hydrograph dominated by rainfall, as compared to snowmelt above 2,300 meters.

The increased occurrence of super-saturation during convective storms, as well as concentrated overland flow, can contribute to the likelihood of occurrence of debris flows.

Debris flows are more likely to be triggered in the unglaciated zones due to convective storms. Super-saturation and overland flow are the dominant debris-flow initiating processes.

Wildfires will also more likely occur in the unglaciated zones due to more vegetation, which may also contribute to the likelihood of debris flows.

Debris will contribute sediment directly to the channel due to the close spatial proximity of the hillslopes

Floods - Unglaciated Confined Channels

(Information compiled by Liz Gilliam)

Unglaciated regions of the Colorado Front Range lie below 2,300 m, which coincides with a hydrograph dominated by rainfall, as compared to snowmelt above 2,300 meters.

The great amount of discharge contributed to floods generated by convective storms will converge in these confined sections and can be extremely destructive.

Roads are often built directly adjacent to the channel, limiting any lateral migration and flood attenuation.

Large monetary losses can occur due to infrastructure losses.

Erosion and scour of the hillslope toe will enhance debris slides, contributing sediment and woody debris directly to the channel due to the close spatial proximity.

Beaver may have been more active in the unconfined reaches, influencing hydrologic and flood characteristics.

Damage to Gutten Highway during Big Thompson Flood