Journal of Hydraulic Engineering

Hydrologic simulation techniques are combined with field data from rainfall simulation tests to estimate runoff and soil losses from different reclamation treatments. The method presented improves on traditional rainfall simulation plot studies which allow comparisons of treatments, but not estimates of actual soil loss amounts due to realistic precipitation events and antecedent soil moisture conditions. The method is illustrated using data collected on several treatments in the Yampa River Basin coal fields of northwestern Colorado. The field studies used a CSU type portable rainfall simulator. Analysis of field data is extended beyond relative comparisons of the treatments to estimation of actual soil losses using the KINEROS and CREAMS simulation models. Simulation model results provide a better basis for design of such reclamation features as mulch type, mulch rate, slope length and steepness compared with simple analysis of simulated rainfall plot tests.

The results of experiments on nonbuoyant jets discharged horizontally into the lower layer of a stagnant two layer stratified fluid are presented. The stratification consists of a well‐mixed upper layer separated by a finite density jump from a linearly stratified lower layer. Similar flows occur in pumped‐storage reservoirs and Ocean Thermal Energy Conversion (OTEC) discharges in the ocean. The flow consists of a jet which entrains ambient fluid selectively from a layer of finite thickness before collapsing vertically and spreading sideways and forwards as a horizontal density current. Analysis is primarily based on dimensional analysis and length scale arguments, and results are presented to predict whether entrainment from the upper layer occurs, the widths and locations of the entrained flow and depth of the ambient mixed by the jet, the total jet volume flux, and the collapsed layer thickness. The results are applied to an OTEC design; predicted values of collapsed layer thickness, distance to collapse, and terminal dilution were in reasonable agreement with previously measured values.

This paper presents the results of an experimental study on the hydraulics of simple Denil fishways. For the Standard Denil, the characteristic velocity profile that exists in the fully developed flow region is found. A rating curve is developed for the Standard Denil, which would be very useful in the design of Denils over a range of slopes and discharges. A number of other interesting and practical features of the Denil fishways are found. Some results are also obtained for some “nonstandard” Denil designs.

The relationship between scour depth at cylindrical bridge piers founded in cohesionless sediments, and mean approach flow velocity is defined for flows above the threshold of particle motion. Experimental data are collected in which pier size, sediment size and mean approach flow velocity are systematically varied. These data show that the relationship between scour depth and flow velocity differs, depending on whether the bed sediment is ripple forming or non‐ripple forming, and separate functions are identified for each case. Both functions exhibit two scour peaks. These occur at the threshold and transition flat bed conditions. Contrary to previous findings, the maximum scour depth is found to occur at the transition flat bed condition in the case of ripple forming sands. For nonripple forming sediments, however, the maximum scour depth occurs at threshold condition.

The characteristics of cut‐throat flow measuring flumes are examined with special attention to scale effects and the transition submergence at which the flow regime changes from undrowned to drowned. Three flumes were tested over a scale range of 1:4. The results for undrowned flumes indicate a small scale effect at low flow rates only. The noted scale effect is completely eliminated by adjusting the data to correct for dissimilar boundary layer growth. The results for drowned flow indicate no scale effect for relative submergences below 0.85. Above this value an apparent scale effect is noted although it is shown to be of little practical consequence. The value of transition submergence is shown to be nonconstant and dependent on the discharge through the structure. A physical explanation for this behavior is put forward. It is concluded that hydraulic model studies of cut‐throat flumes, are feasible provided the submergence is kept below 0.85 and the entrance and exit conditions are modeled correctly in addition to the flume itself.

Results from a hydraulic model study conducted at the Iowa Institute of Hydraulic Research are reported. The model study was concerned with a proposed design of a 4-pump sump for withdrawal of cooling water from a natural draft cooling tower. The results of the study suggest that potential-flow theory may be used as a guide toward the development of sump design modifications, which may include in-channel turning vanes and perhaps may even be used in the development of the conceptual layout of pump sumps.

The lift force on a moving, heavy particle at the instant when the particle is drawn upwards from near the bottom is been experimentally determined for both smooth and rough-bottom cases in a turbulent open-channel flow. The lift-force data obtained are plotted against the distance from the boundary. It is found that, a) in the smooth wall case, the lift force appears to reach a weak maximum, and then decreases with the distance from the wall, while, in the rough wall case, it decreases appreciably with the distnce from the wall, b) the lift force increases markedly with increasing bed roughness, and c) the extra effect of rough wall upon the lift force tends to disappear with the distance from the wall.