Abstract

Studies of local widening in canyons of the Colorado Front Range near Colorado Springs show detailed evidences of the processes involved.

The streams of the region are typically ephemeral, subject to repeated floods from torrential runoff. These conditions are believed to have been uniform for a long period of time.

The widening results in small, flat-floored basins usually associated with tributary drainage junctions. The basin floors are thinly alluviated except for numerous bedrock exposures along modern and old channels.

The processes involved are:(1) retreat of valley sides by weathering and local corrasion by streams and (2) shifting of channels by plugging the main channel at the basin head and by tributary deposition on the basin floor. Repeated shifting of the channel over a long period and flood scour to an average depth produces a flat bedrock floor.

These valley widening processes are believed to be significant in the development of prominent piedmont flats in the region.

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