Date of Graduation

Fall 2019

Degree

Master of Science in Geospatial Sciences

Department

Geography, Geology, and Planning

Committee Chair

Robert Pavlowsky

Keywords

step-pool morphology, forcing effects, headwater streams, Ozark Highlands, bedrock influence, geomorphic classification

Subject Categories

Geomorphology

Abstract

Understanding headwater streams and their morphology is inherently difficult in contrast to larger streams in downstream valleys. Geomorphic forcing can occur over short distances (<10 >m) and influence channel geometry due to geologic factors such as colluvial inputs and resistant bedrock or biologic factors such as fluvial wood inputs and tree growth in the channel. How and where these geomorphic variables effect step-pool channel characteristics is poorly understood in the Ozark Highlands. Step-pool channel form is typically controlled by gradient, substrate characteristics, and sediment supply. This study reports on a geomorphic assessment of step-pool characteristics and classifies channel form using two different geomorphic classification frameworks in Deer Camp Hollow (0.2 km2) draining the Salem Plateau in Mark Twain National Forest in southeastern Missouri. Topographic surveys, pebble counts, and step measurements were used to assess channel form and forcing effects, along with 0.5 m resolution LiDAR data provided by the U.S. Forest Service. Step-pool forms occur along >80% of the stream length with an average bed slope of 11.5 %, average D90 of 185 mm, and 89 of 122 total steps indicating forcing. Step-spacing typically varies from 1.2 to 3.2 m and decreases with the frequency of forcing. Both classification frameworks suggest that hillslope processes greatly influence channel form, due to their inherently steep slopes and high valley confinement. Furthermore, forced steps had significantly greater step heights (~2x) and H/L ratios (~1.5x). Overall, forcing tends to develop more steps per reach length and higher steps in step-pool channels.

Copyright

© Triston Ralland Rice

Open Access

Included in

Geomorphology Commons

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