USING THE STREAM POWER LAW AND DIGITAL TOPOGRAPHIC DATA TO QUANTIFY LATERAL MIGRATION RATES IN BEDROCK CHANNELS, OREGON COAST RANGE

Meanders in bedrock rivers are typically interpreted as antecedent features, and meander formation is thought to be restricted to low-gradient alluvial rivers. Recent field studies have called this theory into question however, and the extent to which bedrock channels actively meander remains poorly understood. Through the use of the commonly-used stream power law, dz/dt=KA^mSⁿ, where dz/dt is incision rate, K is a dimensional coefficient of erosion, A is upstream drainage area, S is local slope, and m and n are positive constants, we aim to quantify differential incision rates and rates of lateral migration in bedrock channels of the Oregon Coast Range. We analyzed digital elevation models (DEMs) to quantify how channel gradient varies as a function of upstream drainage area. The stream power model predicts that for a given drainage area, channel gradient varies with uplift rate. The landscape in the Oregon Coast Range has been considered to be in dynamic equilibrium because measured sediment yields have been shown to approximate long term uplift rates, thus uplift can be thought of as a surrogate for incision rate. By selecting channels that flow over similar lithology and have similar climates, we eliminate the effects of these variables. Using slope-area data for several small basins, we will test the notion that lateral migration may impose an additional component of incision on stream channels, and attempt to quantify rates of lateral migration. The results of this study will improve our understanding of bedrock channel migration, and provide a means for estimating erosion rates from analysis of digital topographic data.