DOCUMENTING THE DYNAMICS OF WIND RIPPLE EVOLUTION WITH DIGITAL EVOLUTION MODELS

Fields of bedforms such as sand dunes and wind ripples are thought to self-organize from a non-patterned to a patterned state through bedform interactions. Once initiated, bedforms constructively interact to evolve a pattern of progressively larger and more widely spaced bedforms with similar measureable parameters. This research focuses upon the development and evolution of a field of wind ripples within a test area of 50 cm² within a wind tunnel (0.59 m wide and 5.05 m in length) from a smooth bed of well sorted sand. Grain size ranges from 0.03-0.53 mm with a mean size of 0.19 mm. With a flow velocity set to achieve a shear velocity (u_*) of 0.35 m/s, most grains travel in saltation, but the coarsest grains move in creep. An overhead digital camera is used to record ripple-field development. In addition, digital elevation models (DEMs) will be collected at set time intervals using an Optoma 3D LMI scanner with a resolution of 36 microns. The DEMs will be used to produce a time-series of surface evolution. A primary objective is to document the dynamics of ripple initiation during grain transport. Once formed, ripples will be tracked and their evolving morphologies characterized. The type and frequency of ripple interactions through time will be chronicled from these maps.