Bedrock landscape development modeling: Calibration using field study, geochronology, and digital elevation model analysis

Stream power-based models of bedrock landscape development are effective at producing synthetic topography with realistic fluvial-network topology and three-dimensional topography, but they are difficult to calibrate. This paper examines ways in which field observations, geochronology, and digital elevation model (DEM) data can be used to calibrate a bedrock landscape development model for a specific study site. We first show how uplift rate, bedrock erodibility, and landslide threshold slope are related to steady-state relief, hypsometry, and drainage density for a wide range of synthetic topographies produced by a stream power-based planform landscape development model. Our results indicate that low uplift rates and high erodibility result in low-relief, high drainage density, fluvially dominated topography, and high uplift rates and low erodibility leads to high-refief, low drainage density, mass wasting-dominated topography. Topography made up of a combination of fluvial channels and threshold slopes occurs for only a relatively narrow range of model parameters. Using measured values for hypsometric integral, drainage density, and relief, quantitative values of bedrock erodibility can be further constrained, particularly if uplift rates are independently known. We applied these techniques to three sedimentary rock units in the western Transverse Ranges in California that have experienced similar climate, uplift, and incision histories. The ¹⁰Be surface exposure dating and optically stimulated luminescence (OSL) burial dating data indicated that incision of initially low-relief topography there occurred during the last ∼60 k.y. We estimated the relative dependence of drainage area and channel slope on erosion rate in the stream power law from slope-area data, and inferred values for bedrock erodibility ranging from 0.09 to 0.3 m ^(0.2-0.4) k.y.^-1 for the rock types in this study area.