Degree Type

Thesis

Date of Award

2008

Degree Name

Master of Science

Department

Natural Resource Ecology and Management

Major

Environmental Science

First Advisor

Richard Schultz

Second Advisor

Thomas Isenhart

Third Advisor

Matthew Helmers

Abstract

Over the 150 year history of major agricultural activity in Iowa nearly all the native prairie (99.9%) and wetlands (95%) were lost as native plant communities were converted to row-crop agriculture. This major change from perennial to annual upland vegetation was accompanied by broad scale installation of tile drainage intended to remove moisture from saturated wetland soils, increasing available crop land. The increased removal of water by tile drainage accompanied by the increase in surface runoff caused by the loss of permanent soil cover and compaction resulted in an increase in the rate and amount of water entering stream systems. The increase in discharge overtime resulted in a series of channel adjustments (deepening & widening) to accommodate the increase in flow. Sediment contributed due to these channel adjustments, specifically from streambank erosion has been shown to be a major source of sediment in many Midwestern stream systems. The main objective of this study was to determine what impact the major past and present land use practices in the Walnut and Squaw Creek Watersheds were having on the location and rate of severe streambank erosion within the two channel systems. The location and length of severe streambank erosion was mapped along the main channels of each watershed. Eroding lengths were broke down into riparian land use categories: Coolseason grass, warmseason grass, row-crop agriculture, grazed pasture, riparian forest, and grassland-forest mix. Total stream length, sinuosity, and eroding streambank lengths were compared among all land use categories. To estimate streambank recession rates, erosion pins were installed along streambanks in four major riparian land use types identified along the main stem of Walnut Creek. Outcomes of this investigation indicate that areas with high sinuosity located directly downstream of channelized portions of the stream network were subject to longer eroding lengths with higher recession rates than locations higher in the watershed. The two current major riparian land uses most frequently associated with meandered sections of the steam system were riparian forest land and grazed pasture land. Information from this study indicates that areas of stream segmented by alternating patches of channelized and meandered segments likely represent major source areas for streambank derived sediment.

DOI

https://doi.org/10.31274/rtd-180813-7427

Publisher

Digital Repository @ Iowa State University, http://lib.dr.iastate.edu/

Copyright Owner

Jason Alan Palmer

Language

en

Proquest ID

AAI1450147

OCLC Number

229408780

ISBN

9780549422273

File Format

application/pdf

File Size

116 pages

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