Discharge variability and bedrock river incision on the Hawaiian Island of Kaua'i
The Hawaiian island of Kaua’i provides an ideal natural laboratory to evaluate the effects of discharge variability and thresholds on bedrock river incision because it has one of Earth’s steepest spatial gradients in mean annual rainfall and it also experiences dramatic spatial variations in rainfall and discharge variability, spanning a wide range of the conditions reported on Earth. Kaua’i otherwise has minimal variations in lithology, vertical motion, and other factors that can influence erosion. Moreover, river incision rates averaged over million year timescales can be estimated along the lengths of Kauaian channels from the depths of river canyons and lava flow ages. We are characterizing rainfall and discharge variability on Kaua’i using records from an extensive network of rain and stream gauges spanning the past century, and we are using these characterizations to model long-term bedrock river incision on Kauai with a threshold-dependent bedrock river incision law.