Chapter 6: Geologic Controls and Channel Profiles, Eastern Santa Cruz Island

Aaron King & Bridget Tracy

Longitudinal profiles of stream channels give clues to patterns of landscape development. We explored the application of equilibrium theory of longitudinal profile development in the context of the young landscape of eastern Santa Cruz Island. We created a geologic and topographic dataset of the eastern portion of the island to analyze the influence of lithology and accumulated watershed area on longitudinal profiles. We examined these factors to explain the long profiles that were observed using theory. A test of the significance of the difference in slopes between the two dominant bedrock types across all channels resulted in a p-value of 0.038. This level of significance did not hold when the channels were parsed by Strahler order. No strong correlation was found between watershed area and slope. Most of the streams on eastern Santa Cruz Island are unable to adjust quickly enough to establish or maintain equilibrium with uplift and base level fluctuations.