Journal of Hydraulic Engineering

Computer programs developed for dam safety analyses are limited by the accuracy of the input data for the geometric and temporal dam breach characteristics. Data on a number of historical dam failures were collected and analyzed and graphical relationships for predicting breach characteristics were developed for erosion type breaches. The data provides a basis for selecting a breach shape and calculating the breach size and the time for breach development. A relationship is also developed for estimating peak outflows from dam failures. This relationship can be used to verify the methodology and the results of dam safety studies.

In tests of the HL flume with a flat floor approach the discharge ranged from 6.5 percent below published table values for low flows to almost no difference at the maximum head. Generalized discharge equations for HS, H, and HL flumes with chute entrances are given. A direct solution for the effect of submergence on HL flumes is presented in equation form. The hydraulic jump would form on the sloping floor of the chute for all flows. The turbulence in the jump will help keep sediment in suspension and provide mixing for water quality measurements. The depth of ponding over the approach is reduced to half of what it would be if no chute were provided. Sand in the flow will deposit at the lower end of the chute and in the flume. However, satisfactory ratings are provided for flows with concentrations of sediment less than 10,000 ppm.

Tests were conducted on two existing hydroturbines to evaluate turbine venting as a means of oxygenating discharged water. Additions of baffles to the turbine runner hub and to the draft tube wall were made to generate local suction for aspirating air. The effects of these baffles were evaluated in terms of flow rate of induced air, dissolved oxygen uptake and the effect on unit efficiency and output. The results indicated that baffles can be used to increase aspirated air and thus dissolved oxygen uptake, but that there is a related loss in turbine efficiency and capacity.

The theory of characteristics is applied to analyze two‐dimensional unsteady flow over a bed of fine sediment. The sediment is assumed to be so fine that suspension is the predominant mode of transport. An additional equation for sediment diffusion is introduced. As a result, the number of characteristics is increased, but the characteristic directions can be determined without solving high‐degree algebraic equations. Results from a one‐dimensional version of this procedure agreed reasonably well with known data.

The Columbia Hybrid Modeling System was applied to navigation channel shoaling problems at the mouth of the Columbia River estuary. The models were verified to satisfactorily reproduce observed prototype behavior. The adjustment process created a typical year from a statistical analysis of river runoff and waves combined with a typical tide.

Analysis is performed to predict the maximum and equilibrium heights‐of‐rise for vertical round jets discharged into a linearly stratified crossflow. Approximate relations for minimum dilution at the maximum height of rise is also presented. Length scales describing the interaction of a buoyant jet with the crossflow and stratification are presented. Various asymptotic solutions can be developed with the use of dimensional analysis and physical reasoning; their applicability depends upon the relative magnitudes of the different length scales. Experimental results were obtained to determine the values of the appropriate coefficients in the various asymptotic solutions. These were obtained by towing a buoyant jet discharge at constant velocity through a stagnant, stratified fluid. Measurements of maximum and equilibrium rise heights were obtained along with concentration profiles at the maximum height‐of‐rise. The results indicate that the approximate solutions can be applied if the coefficients in the various expressions are allowed to vary; this variation may be small enough to neglect for many practical applications.