Response of alluvial rivers to active tectonics

In order to investigate effects of active tectonics on alluvial rivers, a series of experiments were performed on braided, meadering and confined straight channels, and examinations of alluvial rivers flowing through areas of surficial deformation were conducted. The experimental braided channel responded to anticlinal uplift across the channel with degradation and terrace formation in the central part of the uplift. A strongly braided pattern developed in the downstream reach, where aggradation and slope steepening occurred. With subsidence, aggradation in the central reach was the main response. A strongly braided pattern formed upstream, and transverse bars developed in downstream side of the subsidence axis. The experimental meandering channel responded to valley slope steepening with a sinuousity increase. Bank erosion and point-bar growth occurred downstream of the anticlinal axis and upstream of the synclinal subsidence. Based on experimental results and field examples, models of river response to two common types of active tectonic movements (anticlinal uplift and synclinal subsidence) were developed for different types of alluvial rivers.