The Wrinkles of Aging Landscapes

Processes that create and transport sediment interact with climate and tectonics to generate the earth’s varied topography. Geomorphologists observe the size and shape of topographic features to infer the relative importance of these controlling factors, but often lack quality data and suitable mathematical models. These limitations are especially apparent when studying deep-seated landslides because their location and motion can change rapidly with time.

Adam Booth is developing a numerical landscape evolution model to investigate the behavior of terrain prone to earthflows – a type of slow deep-seated mass movement – under different tectonic and climatic regimes. The model consists of mathematical geomorphic transport laws describing earthflow movement, soil creep, gully incision, and bedrock weathering linked through a statement of mass balance. Feedbacks and interactions between these four processes produce a wide range of modeled landscapes, and both rates and spatial patterns of sediment transport can be inferred from the modeled processes’ relative intensities. To tie modeled landscapes to real landscapes, Adam utilizes high-resolution topographic data acquired with airborne Light Detection and Ranging (LiDAR). Working with Josh Roering’s research group, he is currently applying his model to a study site along the Eel River, northern California, and will soon begin work in the upper Waipaoa catchment, New Zealand. Preliminary results from the Eel River site highlight key behaviors of earthflow-prone landscapes: earthflows are most effective at lowering the land surface elevation on mid to upper hillslopes, while gullying is necessary to remove sediment from lower hillslopes and generate hillslope profile concavity. Future work will address several important aspects of long-term landscape evolution including how earthflows interact with channelized processes to set ridge-valley structure, and how the frequency-magnitude statistics of earthflows change with climate and tectonics.