Like Water on a Rock: Correlating Geology and Channel Patterns in the Tuolumne Watershed

The channel patterns of the Tuolumne Watershed vary greatly, from the steep reaches of the “Grand Canyon” to the flat meandering channels of Tuolumne Meadows and the Central Valley. Spatial analysis was used to extract stream metrics and channel patterns as they occur over different geologic units. The Tuolumne Watershed was divided into six geologic categories based on age and lithology. Three primary channel patterns, including stream gradient, drainage density, and channel type were determined for the hydrology within each geologic unit. While stream gradient was found to have no correlation with rock type, drainage density and channel type were found to systematically change with rock type suggesting that lithology influences these stream network characteristics.