Journal of Hydraulic Engineering

The ways in which rivers adjust their hydraulic roughness to accommodate only loosely correlated changes in their water and sediment discharges are discussed. An assessment of the current status of river engineering leads to the conclusion that the major deficiencies of mathematical models of river flow have been their failure to represent the dependence of friction factor on sediment discharge or concentration, and to include temperature and channel‐curvature effects. It is argued that the data and computational resources now are at hand to permit development of more inclusive analyses of alluvial‐channel flow. A recently developed computer‐based predictor for river‐flow sediment discharge and friction factor, and an analytical model of flow in river bends are outlined. Reflections on Rouse's research and writing conclude the paper.

Monthly streamflow records at a site are sometimes extended by exploiting interstation correlation of streamflow, often through simple linear regression with a base station having a long‐term record. An approach is presented which selects a base station from among several in a region for filling in missing data. It differs from traditional approaches in that different stations can be selected as the base station to fill in different values. The approach also provides a decision rule for using only flow values from the same month or all flow values in developing the extension equation used for estimating a particular missing value. A previously presented extension equation to minimize variance bias of the flows estimated at the short‐record station is shown to be applicable to this technique. The possibility of using this extension equations to adjust the results of multiple regression in order to account for variance reduction is also suggested.

Combining the neat representation of boundary geometry by finite‐element models with the advantage of fast numerical solution in finite‐difference models, an irregular‐grid finite‐difference model is developed to solve the hydrodynamic equations for a homogeneous shallow lake. With a coarse irregular grid consisting of only 52 points the model is used to simulate storm surges on Lake Geneva during a sixty‐hour episode of strong north‐easterly winds. The simulation results are compared with the actual water level observations.

Lateral and vertical stability are assessed for 100 unlined channels, in different parts of the United States, that were relocated by highway agencies 10 years or more before assessment. Median length of natural channel cut off by relocation is 50 times natural channel width, or about 2,100 ft (650 m). Of all the relocated channels, banks are assessed as stable at 78 percent and unstable at 22 percent; of the shorter relocated channels (less than 50 channel widths), banks are assessed as stable at 84 percent and no significant degradation was observed. After an initial period of adjustment, the relocated channels tend to have about the same stability as that of the prior natural channel. Increase in channel slope by relocation is not clearly related to instability; and stable channels of similar drainage area range widely in slope. Factors commonly associated with instability are: (1) Bends in channel; (2) erodibility of bed‐bank materials; (3) floods of large recurrence interval; and (4) instability of natural channel before relocation.

Western Kansas is underlain by the Ogallala aquifer that produces water of good quality. Many large‐capacity wells have been drilled for irrigation, industrial, and municipal use. Ground‐water withdrawals exceed recharge and water levels are declining at an average rate of 3 ft/yr. Five ground‐water management districts were formed to help control and manage this resource. Management policies that have the most effect on withdrawals are well spacing and a planned rate of ground‐water depletion. The depletion policies in effect limit development to a 40% depletion of the aquifer in 20 to 25 yr or to a “safe yield” concept.

Meander bends of high amplitude in alluvial rivers often display a high degree of coherency. The only analytical equation heretofore available to describe such bends is the sine‐generated curve, which has no rigorous derivation in the context of rivers. Herein a nonlinear “bend equation,” based on a dynamical description of flow in bends and a kinematical description of bank erosion, is used to describe channel migration. This equation admits solutions of constant amplitude that migrate downstream with constant speed. The solution at high amplitude displays a prominent skewing that reveals the direction of flow. At low amplitude, the solution reduces to the sine‐generated curve.

The theory of river ice jams, as developed by several investigators over the past two decades, is reviewed and two methods for analyzing case studies are developed. The first method is based on a dimensionless equation that relates measurable ice jam characteristics. The second method compensates for the lack of measured thickness values for breakup jams by introducing a relationship between the hydraulic roughness and the thickness of a jam, based on data by others with respect to freeze up jams. These two methods of analysis are subsequently applied to several case studies performed in recent years by the writer and others. The results support the theory and at the same time show satisfactory consistency in the respective values of various coefficients obtained by the two methods. Procedures for practical application of the present results are outlined and assessed by means of examples.

An empirical equation is derived for horizontal drains. The equation is based on results of finite element analysis and verified by a set of laboratory experiments. The empirical equation provides a simple and quick way to calculate the downstream water depth as a function of the drain spacing and slope of the impermeable bed. The equation is useful for planning or design, purposes, or both, when horizontal drains are used for lowering the groundwater table in slopes.

Previously reported data from sandbed rivers, gravel-bed rivers and laboratory flumes are reviewed. In this technical note, the data are supplemented with data sets from two different laboratory flumes. The first data set is for weak sediment transport with sand. The second set is for a steep channel with large relative roughness.

Energy losses in irregular channels are due only partly to boundary shear and additional energy loss results from the effects of bends, irregularities, and changes in the cross section. Experiments which were designed to clarify some aspects of energy losses in irregular channels are described. It is demonstrated that a certain type of irregularity in form, i.e., one in which the cross-sectional area of flow is kept constant or varies in such manner that there is no flow separation, does not contribute to energy losses.

A three-dimensional mathematical model is presented for calculating the flow and heat transfer in channels under the influence of buoyancy. The model is applied to the coaxial slot discharge of heated water into rectangular open channel flow. It is found capable of simulating the main features of this flow which include the lateral mixing of warm and ambient cold water and the rise and spreading at the surface of the warm water.

Several point rainfall estimation techniques including the conventionally used arithmatic average and normal ratio methods, inverse-distance method, modified normal ratio method, and method of using linear programming model are applied to the Sierra-Nevada mountainous region. In the study area, the elevation difference between the rain gages range from 70 ft to 1750 ft (21m to 534m) and the distance from 10 miles to 35 miles (18km to 63km). It is found that the recently advocated inverse-distance method fails to provide a desirable result. A method is proposed which takes into account the effect of topographic elevation variation for the region. Also, the issue about the number of index stations to be used in the estimation procedure is explored and discussed.