Journal of Hydraulic Engineering

An analysis to predict the hydraulic performance of a tangential vortex‐inlet which is relatively simple in shape and compact in size is presented. The theory agrees with the experimental data. A relation to determine the dropshaft diameter for a design discharge is given.

The issue of “how fast” reversible chemical reactions must be before “instantaneous equilibrium” may be assumed in ground‐water contamination problems is investigated. An example multicomponent model is used to study the requirements that must be placed on a system's Damkohler numbers to guarantee that reaction mechanisms are not kinetically limited. Analysis is presented for multicomponent transport problems using soluble complexation, ion exchange, and surface complex formation reactions. Results are presented to illustrate that instantaneous equilibrium is an excellent approximation when nondimensionalized reaction rates exceed 100.

The SEDLAB simulation model, which represents overland runoff and erosion from agricultural watersheds, has been revised to include dynamic overland and channel flow resistances, new infiltration methods, and improved sediment transport equations. Two parameters which represent overland and channel flow resistance in the simulation model were calibrated from event data on W‐1 near Treynor, Iowa, and related to observed roughness features on the watershed. These parameters were found to change in a manner which represented the event‐to‐event variation in flow resistance due to tillage, rill development, and changes in residue, crop, and vegetative cover. The methods and parameters developed on watershed W‐1 to represent flow resistance were applied to events on adjacent W‐2 near Treynor, Iowa, with good results. The flow resistance parameters determined in this study are representative of watersheds with loessial soil, contoured fields, and a corn crop. Further testing on other agricultural watersheds is needed to define the dynamic variations of flow resistance caused by antecedent rainfall, runoff, crop, and land management.

A method is presented that makes the classification of bed forms, the prediction of the bed‐form dimensions and the effective hydraulic roughness of the bed forms feasible. The proposed relationships are based on the analysis of reliable flume and field data. A verification analysis using about 1,500 (alternative) reliable flume and field data shows good results in predicting the hydraulic roughness (friction factor). For field conditions, the proposed method yields considerably better results than previously proposed methods, which are reviewed here. The proposed method has also been used to predict the flow depth and the total bed‐material load.

Hydraulic jump characteristics were measured over several artificially roughened test beds in a horizontal rectangular flume with smooth side walls. A smooth test bed, two strip roughness test beds and three densely packed gravel test beds provided a relative roughness range from 0.0–0.9. The testing program involved some 200 hydraulic jump observations which included flow rate, upstream depth, tailwater depth and jump length. Observations showed that boundary roughness reduces both the sequent depth and the length of a hydraulic jump, and that the observed reductions were related to both Froude number and the degree of roughness. The observed hydraulic jump characteristics were consistent with theory, and a proposed approximation for a theoretical hydraulic jump equation was found to compare favorably with the observed characteristics.

An analysis is provided for the spatial variations of flow resistance and other flow characteristics through curved channels reflecting the effects of transverse circulation. Among the assumptions in the analysis, the transverse velocity profile is assumed to remain similar during circulation growth and decay. A mathematical model for computing such variations is developed and it has been verified using limited available data. The results demonstrate that flow resistance or energy expenditure produced by transverse flow can be very significant even for mild curves without flow separation. Because of the important effects of channel curvature, analytical methods developed in this model provide useful techniques for studies of river morphology and sediment transport in meandering streams.

The basic assumptions used in the derivation of bedload or gravel transport equations are reviewed and examined to determine their validities. Laboratory data indicate that unit stream power is more desirable than other variables for the determination of gravel transport rate or concentration. A dimensionless unit stream power equation for gravel transportation is developed based on well established theories in turbulence and fluid mechanics. Comparison between this new equation and other well‐known equations indicates that the new dimensionless unit stream power equation for gravel transportation is more accurate than others for the gravel data compared in this paper.

The writers demonstrate how the geometric and hydraulic properties of river reaches, which are required in flood routing when using the Saint‐Venant equations, may be identified using optimization methods. It is suggested that these optimization methods may prove an attractive alternative to the costly and time‐consuming survey work or uncertainty, or both, that often accompany the estimation of numerical river model parameters. The writers adopt the four‐point finite difference scheme of Amein and Fang (2) to solve the Saint‐Venant equations. They report on an investigation into the selection of time and space increments in order to limit the finite‐difference error in the solution. The optimization process involves minimizing the errors in depth and discharge of the downstream routed hydrograph. Two objective function criteria are compared, namely minimax and least‐squares. Four optimization parameters are used, two representing channel geometry and two its hydraulic properties. Five flood events are optimized and generally the two optimization methods give consistent results, although there are differences between winter and spring floods.

This paper describes the nature of saline wedge formation in tunneled ocean sewage outfalls. A momentum flux equation is used to determine the sewage discharge required to purge a saline wedge from an outfall tunnel in which the risers leave from the soffit. It is shown that the purging discharge is generally much greater than the flow required to prevent saline intrusion into the risers. Laboratory experiments are described which confirm the validity of the purging criterion. Means by which the purging flow may be minimized are also considered.

Overflow depth on a levee crown is studied using one dimensional analysis of a stream with side overflow. There are two typical water surface profiles which depend only on channel properties and not on flow rate. Their approximate solutions are presented and examined in detail. Applicability of the theoretical results were verified with experimental flume data. The relationship between overflow depth and channel properties was calculated using a one dimensional momentum equation. Two important parameters concerned with a bankfull flow include the Froude number and channel $\mathrm{width}\times \mathrm{slope}/\mathrm{channel}$ depth.

The flood of July 26, 1981, in Tanque Verde Creek east of Tucson, Arizona, that killed eight people near Tanque Verde Falls was just a small one for this stream. Dangerous floods are not necessarily large ones; two much larger floods occurred there within a week. Floods can travel for miles at rates of rise and speeds too great for a person to escape from rough stream channels. Reports by survivors and initial observations by hydrologists indicated a large flood had occurred. However, when records of streamflow at a gaging station downstream were analyzed, it was apparent the killer flood was small and the peak discharge could be expected to be exceeded at least once every 2 yr. Storm and drainage‐basin characteristics are important in the production of dangerous floods. Survivors' reports of a wall of water were corroborated by hydrologic and hydraulic flood routing.

Tests of emergency heat removal pump sumps of nuclear power stations were conducted. A variety of approach flow patterns and different sump geometries tested gave rise to a wide range of circulation contributing to vortices of varying types and strengths. This paper presents the air-ingestion data for a wide range of Froude numbers and circulations. These data may be useful in obtaining indications of maximum likely air ingestions due to free-surface vortices at a pump intake.

Many investigators have looked at the relationship between precipitation and elevation, and other topographic factors that influence precipitation. However, in most cases, these studies have been restricted to a particular state, area, or watershed. The writer feels that the time has come to generalize the precipitation-elevation relationships for various regions, and to determine whether the regional variabilities are significant. The data presented in this paper are a step in such a regional evaluation.

Einstein's bed load function for computing total load discharge per unit width requires computation of Einstein's integrals I₁ and I₂. The integration method proposed in this paper employs isolation of the singular point. It is shown that accurate numerical estimates of Einstein's integrals for extremely large integrands can be obtained by summing the exact series-expansion integral near the lower integration limit and the numerical integral over the remaining upper integration zone.