The Relationship between Drainage Density, Erosion Rate, and Hilltop Curvature: Implications for Sediment Transport Processes

Abstract:

Drainage density is a fundamental landscape metric which describes the extent of the fluvial network. How drainage density varies with erosion rate controls the transit time of water and sediment through catchments, influencing the rate of flood response and biogeochemical cycling. This relationship also has profound implications for landscape response to transient forcing. We extract drainage density for five field sites in the USA with a wide range of climatic and lithological characteristics: Feather River, CA; San Gabriel Mountains, CA; Boulder Creek, CO; Guadalupe Mountains, NM; and Haddington Creek, ID. We find that there is a significant positive relationship between drainage density and erosion rate across every field site. These relationships suggest a non-linear relationship between erosion rates and channel slope with an exponent greater than 1. These results are supported by numerical modeling using the Channel-Hillslope Integrated Landscape Development (CHILD) model. Our modeling results also suggest that non-linear sediment transport fundamentally affects the dominant length scales forming ridges and valleys.