Downstream Changes in Sediment Character in a High Energy Mountain Stream Channel

Rapid downstream changes in particle size, form, sorting, and grain size distributions are demonstrated to occur in the bed sediments of Two O'Clock Creek, a small stream in the Canadian Rockies. These changes are related to distance from the stream mouth, bed slope, and rock lithology. Pebble size, maximum projection area, and sorting alter systematically downstream while pebble roundness and flatness do not change. Particle size, maximum projection area, roundness, and sorting correlate significantly with bed slope, with the larger, better rounded and more poorly sorted gravels occuring on the steeper channel segments. Rock lithology correlates more highly with pebble size, maximum projection area, roundness, and flatness than either distance from the stream mouth or local bed slope, proving it to be the single most important factor influencing particle character. The high degree of variance displayed by the relationships most probably reflects the addition of fresh material to the stream along its course.