Physical habitat dynamics in four side-channel chutes, lower Missouri River

Abstract

Construction of side-channel chutes has become a popular means to rehabilitate habitat of the Lower Missouri River. We studied various aspects of hydrology, hydraulics, and geomorphology of four side-channel chutes to document a range of existing conditions in the Lower Missouri River. The Cranberry Bend side-channel chute has existed for at least 40 years and is an example of a persistent, minimally engineered chute. The Lisbon Bottom side-channel chute is a young chute, created by extreme floods during 1993 -1996, and allowed to evolve with minimum engineering of inlet and outlet structures. The Hamburg Bend and North Overton Bottoms side-channel chutes were constructed in 1996 and 2000, respectively, as part of the Missouri River Bank Stabilization and Navigation Fish and Wildlife Mitigation Project.These side-channel chutes provide increased areas of sandbars and shallow, slow water -habitats thought to be substantially diminished in the modern Missouri River. Depths and velocities measured in side-channel chutes are also present in the main channel, but the chutes provide more areas of slow, shallow water and they increase the range of discharges over which shallow, slow water is present. The 3.6 km long Lisbon Bottom chute provides as much as 50% of the entire shallow water habitat that exists in the encompassing 15 km reach of the river. At Cranberry Bend and Lisbon Bottom, the side-channel chutes provided 10 -40% of the available sandbar area in the reach, depending on discharge.Each of the side-channel chutes shows evidence of continuing erosion and deposition. The longevity of the Cranberry Bend chute attests to dynamic stability -that is, a chute that maintains form and processes while shifting in position. The Hamburg chute similarly shows evidence of lateral movement and construction of flood plain to compensate for erosion. The Lisbon Bottom chute -the most intensively studied chute -appears to have achieved an equilibrium width and continues to migrate slowly; however, evidence of aggradation indicates that the chute has not reached an ultimate form, and may be continuing to adjust to altered hydrology and sediment availability. The North Overton Bottoms chute is the newest in the study. In its originally constructed form, the North Overton Bottoms pilot chute was extremely stable, even while being subjected to two floods in excess of 2-year recurrence interval and after accumulating large, potentially destabilizing large woody debris jams. Ongoing adaptive re-engineering of the North Overton Bottoms chute has prevented assessment of how the chute might have adjusted its form in the absence of intervention.

Age‐0 Sturgeon Accessibility to Constructed and Modified Chutes in the Lower Missouri River

“…The natural chutes included Lisbon (rkm 351; located on the next bend upstream of Jameson) and Pelican (rkm 26). Lisbon was formed by high water events during 1993-1996 (Jacobson et al 2004) and is relatively young compared with Pelican, which was present on maps as early as the 1890s (Missouri River Commission 1895). Although these two chutes formed naturally, they are considered modified as control structures were also constructed in these chutes.…”

Comparisons of zooplankton and phytoplankton in created shallow water habitats of the lower Missouri River: implications for native fish

“…Backwaters are floodplain features that are connected to the river on the downstream end but typically disconnected at the upstream end under normal flow conditions. Chutes are a side channel of the river which diverts flow from the main channel through the chute, and back into the main channel, thus creating an island (Morris et al 1968;Jacobson et al 2004;Sterner et al 2009;Grenfell et al 2012). While our understanding of the importance of backwaters is much greater than that of chutes, chutes are the only SWH management action that has the potential to produce some of the extensive lateral migration (alluvial cut and fill dynamics) that characterized the pre-engineered Missouri River.…”

“…Under natural, historically documented conditions SWH existed in many forms in the Missouri River including backwaters, chutes, and within-channel habitats (Jacobson et al 2004). As a result of channel modifications, however, surface area of the Missouri River was reduced by 67 % and most of this reduction resulted from the elimination of relatively productive chute and slack water areas (Morris et al 1968).…”

“…While our understanding of the importance of backwaters is much greater than that of chutes, chutes are the only SWH management action that has the potential to produce some of the extensive lateral migration (alluvial cut and fill dynamics) that characterized the pre-engineered Missouri River. For example, chutes provide physical changes including sediment deposition downstream, eroding banks, and introduction of large woody debris into the river (Jacobson et al 2004). …”

Characteristics of suspended and streambed sediment within constructed chutes and the main channel at Upper Hamburg and Glovers Point Bends, Missouri River, Nebraska, 2008

“…The suspendedsediment concentration measured in the Missouri River at GLOVR on June 5 was much higher than that measured at Sioux City, most likely because the Floyd River (not shown), which enters the Missouri between the Sioux City streamflowgaging station and the GLOVR study site, was contributing high flows. When suspended-sediment concentrations from the period of record (water years 1972to 1976, 1992to 2000, and 2004to 2008at Sioux City and water years 1972to 1976, and 1992 to 2008 at Nebraska City) at each streamflow-gaging station are compared using a standard t-test with unequal variance, the difference was significant (p-value of 0). When daily suspended-sediment concentrations from the two streamflowgaging stations for the period May 1, 2008 through Sept 30, 2008 were compared using the standard t-test with unequal variance, the difference was again significant (p-value of 4.37x10 -11…”