Streams erode their alluvial beds to reach capacity and begin to downcut through bedrock, using the sediment load as abrasive tools. Local relief increases, thereby increasing sediment volumes delivered to the channel. The increased sediment load provides more abrasive tools and, as long as streams remain under capacity, bedrock wear rate continues to increase, further increasing relief. Greater relief leads to increased frequency and magnitude of bedrock-involved landslides. This run-away system is checked when hillslope processes begin to provide too much sediment to streams.
Channels begin to alluviate, bedrock erosion slows, and local relief lowers.
Ultimately, a landscape is reached in which rivers delicately adjust local relief to provide just enough abrasive tools to erode their bedrock floors at the bedrock uplift rate. This is a landscape where bedrock rivers are at grade. For plucking, none of this argument applies. The purpose of this proposal is to conduct a field test to better define the mechanisms of bedrock erosion occurring in streams draining the Central Range of Taiwan, and to quantify the amount of bedrock erosion as a function of stream hydraulic and sediment transport variables. We propose to set up a catchment scale experiment in the Central Range of Taiwan, in order to quantify the controls on fluvial incision and to establish how those controls interact to determine the rate of channel lowering.