First publication arising from MOST work accepted in Hydrological Processes

"A portable experimental hillslope for frozen-ground studies"


Abstract: Frozen ground hydrological effects on runoff, storage and release have been observed in the field and tested in numerical models, but few physical models of frozen slopes (at scales from 1-15 m) exist partly because the design of such an experiment requires new engineering design for realistic whole-slope freezing and physical model innovation. Here we present a new freezable tilting hillslope physical model for hydrological system testing under a variety of climate conditions with the ability to perform multiple (up to 20 per year) freeze/thaw cycles. The 4 by 2 m hillslope is mobile and tiltable based on a modified tri-axle 4.88 m (16’) dump trailer to facilitate testing multiple configurations. The system includes controllable boundary conditions on all surfaces; examples of side and base flow boundary conditions include permeable membranes, impermeable barriers, semi-permeable configurations as well as constant head conditions. To simulate cold regions and to freeze the hillslope in a realistic and controlled manner, insulation and a removable freezer system are incorporated onto the top boundary of the hillslope. The freezing system is designed to expedite the freezing process by the addition of a 10,130 KJ (9,600 BTU) refrigeration coil to the top-center of the insulated ceiling. Center placement provides radial freezing of the hillslope in a top-down fashion, similar to what natural systems encounter in the environment. The perimeter walls are insulated with 100 mm of spray-foam insulation, while the base of the hillslope is not insulated to simulate natural heat fluxes beneath the frozen layer of soil. Our preliminary testing shows that covers can be frozen down to -10°C in approximately 7 days, with subsequent thaw on a similar timeframe.