Hydrographic Surveys at Seven Chutes and Three Backwaters on the Missouri River in Nebraska, Iowa, and Missouri, 2011–13

Abstract

The U.S. Geological Survey cooperated with the U.S. Army Corps of Engineers (USACE), Omaha District, to complete hydrographic surveys of seven chutes and three backwaters on the Missouri River yearly during 2011–13. These chutes and backwaters were constructed by the USACE to increase the amount of available shallow water habitat (SWH) to support threatened and endangered species, as required by the amended “2000 Biological Opinion” on the operation of the Missouri River main-stem reservoir system. Chutes surveyed included Council chute, Plattsmouth chute, Tobacco chute, Upper Hamburg chute, Lower Hamburg chute, Kansas chute, and Deroin chute. Backwaters surveyed included Ponca backwater, Plattsmouth backwater, and Langdon backwater. Hydrographic data from these chute and backwater surveys will aid the USACE to assess the current (2011–13) amount of available SWH, the effects river flow have had on evolving morphology of the chutes and backwaters, and the functionality of the chute and backwater designs. Chutes and backwaters were surveyed from August through November 2011, June through November 2012, and May through October 2013. During the 2011 surveys, high water was present at all sites because of the major flooding on the Missouri River. The hydrographic survey data are published along with this report in comma-separated-values (csv) format with associated metadata.

Hydrographic surveys included bathymetric and Real-Time Kinematic Global Navigation Satellite System surveys. Hydrographic data were collected along transects extending across the channel from top of bank to top of bank. Transect segments with water depths greater than 1 meter were surveyed using a single-beam echosounder to measure depth and a differentially corrected global positioning system to measure location. These depth soundings were converted to elevation using water-surface-elevation information collected with a Real-Time Kinematic Global Navigation Satellite System. Transect segments with water depths less than 1 meter were surveyed using Real-Time Kinematic Global Navigation Satellite Systems. Surveyed features included top of bank, toe of bank, edge of water, sand bars, and near-shore areas.

Discharge was measured at chute survey sites, in both the main channel of the Missouri River upstream from the chute and the chute. Many chute entrances and control structures were damaged by floodwater during the 2011 Missouri River flood, allowing a larger percentage of the total Missouri River discharge to flow through the chute than originally intended in the chute design. Measured discharge split between the main channel and the chute at most chutes was consistent with effects of the 2011 Missouri River flood damages and a larger percent of the total Missouri River discharge was flowing through the chute than originally intended. The U.S. Army Corps of Engineers repaired many of these chutes in 2012 and 2013, and the resulting hydraulic changes are reflected in the discharge splits.

First posted March 2, 2015