PATTERNS IN THE SAND: BEDFORMS OF THE COLORADO RIVER IN GRAND CANYON

Bedforms are features that are found at the interface between fluids (flowing water or air) and sediment beds (mud, sand, gravel), and are the result of the bed material being moved by the fluid. A variety of bedform features have been documented on Earth and other planets, including (from small to large) ripples, dunes, and waves. They are almost ubiquitous in nature, found at the bottom of rivers and streams, lakes and seas, below glaciers, in deserts, and preserved in rocks. The dynamics, patterns and form of these features have fascinated and inspired scientists, mathematicians and artists for centuries. Groundbreaking technological improvements in sonar mapping systems now allow us to see bedforms in deep water at unprecedented detail over large scales.

On the bed of the Colorado River in Grand Canyon, sandy bedforms are found over a continuum of scales, interacting with turbulent flows and rocks, and changing form as they move downstream into and out of deep pools, and around bends and obstacles. These bedforms get destroyed by rapids, only to reform downstream in a myriad of patterns and sizes. We have surveyed bedforms over approximately 260 kilometers of the riverbed through Grand Canyon National Park. The maps were constructed using a state-of-the art multibeam echosounder technology. Modern visualization software allows scientists to display these features and reveal the natural three-dimensional beauty of channel forms. We present examples of these features and the techniques used to generate the images.