Date of Graduation

Summer 2019

Degree

Master of Science in Geospatial Sciences

Department

Geography, Geology, and Planning

Committee Chair

Robert Pavlowsky

Keywords

sediment contamination, mining, Old Lead Belt, Big River, legacy sediment, sedimentation rates

Subject Categories

Environmental Monitoring | Geomorphology | Sedimentology

Abstract

Floodplain sedimentology and geochemistry can indicate the age of sediment layers to evaluate the history of human-caused sedimentation in a watershed. While the Ozark Highlands of Missouri has had a long history of settlement and land disturbance beginning in the early 1800s, there are few studies that have investigated the effects of these anthropogenic activities on river form and legacy sedimentation. The goal of this study is to characterize the sediment properties and geochemical trends in post-settlement floodplain deposits along lower Big River in Jefferson County, Missouri. This study evaluated trends of sediment properties at 3 cm intervals in a 4 m floodplain core. In addition, eleven cores were collected and assessed at 5 to 20 cm intervals from four alluvial landforms including near-channel bench (1 core), floodplain (7), back-swamp (1), and low terrace (2). Stratigraphic indicators used to date the deposits included: (i) Lead and zinc profiles linked to the history of ore production in the Old Lead Belt; (ii) 137Cs activity released by atomic bomb testing in the 1950-60s; (iii) Sand content peaks caused by large floods recorded by a long-term discharge gage; and (iv) Land use records published in the agricultural census. From about 1860 to 1917 floodplain deposition rates were relatively low ranging from 1.6 to 2.4 cm/yr. Deposition rates peaked between 1947 and 1950 averaging 6.7 cm/yr. After 1957, sedimentation rates decreased to an average 0.77 cm/yr through 2018. Peak sedimentation rates in the lower Big River occurred 20-30 years after peak land use disturbance in the watershed suggesting that river response to European settlement occurred later in lower main channel compared to headwaters streams.

Copyright

© Miranda M. Jordan

Open Access

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