Hydraulic geometry and low streamflow regimen

Unit stream power defined as the time rate of potential energy expenditure per unit weight of water of a natural stream has been studied intensively in this report. It is shown that the distribution and variation of unit stream power have a determinate effect on the behavior of a natural stream. The unit stream power can be regulated by a stream through the combined process of meandering, forming pools and riffles, and carving a concave longitudinal stream bed profile. A study of the Kaskaskia River basin shows that sinuosity increases in the downstream direction by meandering. Field measurements made along the Middle Fork Vermilion River indicate that unit stream power can be minimized by the formation of pools and riffles. The hydraulic geometry--unit stream power equations developed for 9 river basins in the United States show that un-it stream power in a river basin decreases with increasing frequency of flow and drainage area. These results are evidence of different levels of self adjustment made by a natural stream to minimize its unit stream power in accordance with the law of least time rate of energy expenditure. The calculated dimensionless dispersion coefficients--at 11 gaging stations in the Kaskaskia River Basin show that the coefficients increase with increasing width-depth ratio.U.S. Department of the InteriorU.S. Geological SurveyOpe