Perennial-streamflow characteristics related to channel geometry and sediment in Missouri River basin

Abstract

Geometry, channel-sediment, and discharge data were collected and compiled from 252 streamflow-gaging stations in the Missouri River basin.The stations, with several exceptions, have at least 20 years of streamflow records and represent the complete ranges of hydrologic and geologic conditions found in the basin.The data were analyzed by computer to yield simple and multiple power-function equations relating various discharge characteristics to variables of channel geometry and bed and bank material.The equations provide discharge as the dependent variable for the purpose of making estimates of discharge characteristics at ungaged sites.Results show that channel width is best related to variables of discharge, but that significant improvement, or reduction of the standard errors of estimate, can be achieved by considering channel-sediment properties, channel gradient, and discharge variability.The channel-material variables do not have uniform effects on width-discharge relations and, therefore, are considered as sediment-data groups, or stream types, rather than as terms in multiple power-function equations.Relative to streamflow, narrowest channels occur when streams of steady discharge transport sufficient silt and clay to form stable, cohesive banks but have a small bed-material load of sand and coarser sizes.Stable channels also are associated with relatively large channel gradients, relatively large channel roughness, and armoring of bed and bank by coarse particle sizes.The widest, most unstable channels are ones that apparently transport a large bedmaterial load of sand sizes.The downstream rates of change of width with discharge reflect these trends, indicating that a given bed-material load necessitates a minimum width for movement of tractive material.Comparisons of standard errors of estimate given here with similar results from regional studies are variable.It is assumed, however, that a benefit of this study is that the use of the equations is not limited to the Missouri River basin.Besides the principal utility of estimating discharge characteristics of ungaged streams, the equations given here can be used for the design of artificial channels and can be used as a basis of predicting channel changes resulting from upstream alterations of the basin or channel.Apple Creek near Menoken, N. Dak.........