Landscape evolution of Earth's critical zone
Earth's Critical Zone is a living, breathing, constantly evolving boundary layer where rock, soil, water, air, and living organisms interact. My research focuses on understanding the primary drivers of the landscape asymmetry of Susquehanna Shale Hills Critical Zone Observatory (SSHCZO), which is a forested, first-order catchment with shale bedrock in a temperate climate. My approach includes (1) developing a landscape evolution model and (2) using analytic and numerical experiments to understand the factors that cause the landscape asymmetry of the SSHCZO.
Earth's Critical Zone is a living, breathing, constantly evolving boundary layer where rock, soil, water, air, and living organisms interact. My research focuses on understanding the primary drivers of the landscape asymmetry of Susquehanna Shale Hills Critical Zone Observatory (SSHCZO), which is a forested, first-order catchment with shale bedrock in a temperate climate. My approach includes (1) developing a landscape evolution model and (2) using analytic and numerical experiments to understand the factors that cause the landscape asymmetry of the SSHCZO.
|
Drivers of the landscape asymmetry of SSHCZO
The topography of SSHCZO is asymmetric, and the key processes that affect the formation of the hillslope asymmetry were not known. I focused on the asymmetry of upper hillslopes where sediment diffusion process dominates hillslope erosion and deposition. I investigated the spatial variation of hillslope sediment transport efficiency under different physical landscape heterogeneity, such as climate, soil, land cover, and hydraulics. Through field measurements and numerical experiments, I simulated aspect-dependent energy fluxes, temperature change in soil zone, and surface-subsurface water flow and found that 1) temperature driven freeze-thaw event is the major factor that causes the asymmetry of north- and south-facing hillslopes and 2) sediment transport by tree-throw event has equivalent contribution to the total sediment transport as the sediment transport due to freeze-thaw but three-throw is not the key factor that cause topographical asymmetry (Zhang et al, (a) under review; Zhang et al, (b) under review). |
Landscape evolution modeling
Previous studies focused more on the interaction of physical processes that govern the surface hydrology and morphodynamics. However, the role of fluid flow in the subsurface layer in controlling sediment transport and landscape evolution is poorly understood. I first designed and built a multi-scale physically based hydrological and morphodynamic model (LE-PIHM) (link here) fully coupled surface and subsurface hydrological processes with morphological processes, such as sediment transport by running water and creep, bedrock weathering, and tectonic bedrock uplift to explore the role of subsurface flow in controlling the morphological features of landscapes.Details refer to Zhang et al., 2016. |
