Evidence for direct suspension of loessial soils on the Columbia Plateau

Wind erosion modelling efforts, both field and wind tunnel studies, have traditionally focused on saltation-based processes for estimating dust emissions from high wind events. This approach gives generally good results when saltation-sized particles, 90 μm to 2 mm mean diameter, are prevalent on the exposed soil surface. The Columbia Plateau, located in north-central Oregon and south-central Washington, is a region with extensive loess deposits where up to 90 per cent of sieved particles (by mass) are less than 100 μm mean diameter. During high-wind events, large amounts of soil and fine particulate matter are suspended. However, field surfaces typically show little evidence of surface scouring or saltation, e.g. soil drifts or covered furrows. Velocity profile analysis of two high-wind events and additional data from a third event show evidence of direct suspension process where saltation is not a major mechanism for eroding soil or generating dust emissions. Surface roughness heights are less than saltation roughness height estimates during peak wind speeds.