The role of precipitation on Bedrock Channel Incision in Kauai, HI

Abstract

Erosion of bedrock channels is frequently modeled with the stream power law, which relates erosion rates to drainage area, slope, and an erosional efficiency coefficient k. The value of k, however, varies with many physical factors and most of these relationships are not well quantified. This study uses a form of stream power dependent on mean annual precipitation. The island of Kauai in the Hawaiian island chain is used as a case study due to the island's steep precipitation gradient and relatively constant lithology. Erosion rates are calculated by constructing splines to approximate the island's shape at the end of the shield-building phase, and these data are used to calculate erosion rates. The precipitation-dependent stream power model is tested with a multiple regression analysis of the Kauai data. Erosion rates are positively correlated with precipitation rates and erosional efficiency is related to precipitation rate by a power of ~0.4.