Effects of hydrology, watershed size, and agricultural practices on sediment yields in two river basins in Iowa and Mississippi

Journal of Soil and Water Conservation
By: , and 

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Abstract

The specific sediment yield (SSY) from watersheds is the result of the balance between natural, scale-dependent erosion and deposition processes, but can be greatly altered by human activities. In general, the SSY decreases along the course of a river as sediments are trapped in alluvial plains and other sinks. However, this relation between SSY and basin area can actually be an increasing one when there is a predominance of channel erosion relative to hillslope erosion. The US Geological Survey (USGS) conducted a study of suspended sediment in the Iowa River basin (IRB), Iowa, and the Yazoo River basin (YRB), Mississippi, from 2006 through 2008. Within each river basin, the SSY from four largely agricultural watersheds of various sizes (2.3 to 35,000 km2 [0.9 to 13,513 mi2]) was investigated. In the smallest watersheds, YRB sites had greater SSY compared to IRB sites due to higher rain erosivity, more erodible soils, more overland flow, and fluvial geomorphological differences. Watersheds in the YRB showed a steady decrease in SSY with increasing drainage basin area, whereas in the IRB, the maximum SSY occurred at the 30 to 500 km2 (11.6 to 193 mi2) scale. Subsurface tile drainage and limits to channel downcutting restrict the upstream migration of sediment sources in the IRB. Nevertheless, by comparing the SSY-basin size scaling relationships with estimated rates of field erosion under conservation and conventional tillage treatments reported in previous literature, we show evidence that the SSY-basin size relationship in both the IRB and YRB remain impacted by historical erosion rates that occurred prior to conservation efforts.

Study Area

Publication type Article
Publication Subtype Journal Article
Title Effects of hydrology, watershed size, and agricultural practices on sediment yields in two river basins in Iowa and Mississippi
Series title Journal of Soil and Water Conservation
DOI 10.2489/jswc.71.3.267
Volume 71
Issue 3
Year Published 2016
Language English
Publisher Soil and Water Conservation Society
Contributing office(s) Lower Mississippi-Gulf Water Science Center
Description 11 p.
First page 267
Last page 278
Country United States
State Iowa, Mississippi
Other Geospatial Iowa River Basin, Yazoo River Basin
Online Only (Y/N) N
Additional Online Files (Y/N) N
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