Response of Channels to Tectonic Activities: Flume Experiments for Bedrock Rivers Affected by Localized Uplift

Abstract

Response of river channels to localized uplift was investigated using flume experiments where the base level was kept constant by a weir at the river mouth. We found three kinds of channel pattern responses; (1) channels that passed through the localized uplift area (generation of a water gap), (2) channels that avoided the uplift area, and (3) formation of a new river with the origin inside the uplift area. It is difficult to predict which type of response will happen in advance because localized uplift causes complicated changes in the channel network pattern, which results in variation of stream power due to interactions between several channels through confluence, avulsion, etc. In terms of the longitudinal profile of the channels, two types of responses were observed: (1) keeping a straight profile in the case of rivers flowing from much higher areas than the uplift area and (2) having a concave-up profile in the case of a newly formed channel running from the uplift area. A straight type of profile was also typical in the case of no uplift, so the concave-up profile is considered to be a “dynamic” equilibrium state that is realized between the descent due to fluvial erosion and the ascent due to uplift.