Showing papers by "Everett V. Richardson published in 1964"

Stream gaging control structure for the Rio Grande Conveyance Channel near Bernardo New Mexico

Abstract: A stream gaging control structure to stabilize and increase the sensitivity of the stage-discharge relation of the Rio Grande conveyance channel near Bernardo, N. Mex., was designed on the basis of model studies and observed field conditions. The structure is designed to eliminate the effect of changes in bed configuration and bed elevation on the stage-discharge relation. These changes have shifted the water-surface elevation at the gaging station as much as 5 feet without a change in discharge. In addition to improving the stage-discharge relation, the structure provides a section where the concentration of the total sediment discharge of the channel can be measured. INTRODUCTION A stream gaging control structure for the Rio Grande conveyance channel near Bernardo, N. Mex., was designed on basis of model studies and field observations of the channel characteristics. The control structure is intended to stabilize the stage-discharge relation and to facilitate measurement of total sediment discharge at a site 5 miles below the channel-head gates. This report describes the problems and site conditions for the conveyance channel, the recommended control design and position in the channel, and the details of the model study. The conveyance channel, which is about 80 feet wide and has bed and banks composed of fine sand (median diameter of 0.24 mm), is designed to transport all riverflows up to about 2,000 cfs (cubic feet per second); the old river channel is now used as a floodway. Flows greater than 100 cfs occupy the full width of the channel; lesser flows occupy only the streambed. Median flow is 280 cfs, and flows exceed 1,000 cfs 16 percent of the time (fig. 29). The bottom slope ranges from about 0.00055 foot per foot in the upper V/2 miles to about 0.0008 123 124 RIVER HYDRAULICS

Sediment Structures Generated by Flow in Alluvial Channels: ABSTRACT

Abstract: The forms of bed roughness which are molded from the bed material by the flow in alluvial channels are broadly classified by their shape and their effect on flow resistance and by the mode of bedload transport associated with the bed form. The most common forms of bed roughness include ripples, dunes, a transition roughness as the dunes change to a plane or flat bed, plane bed, standing waves, and antidunes. The forms of bed roughness change from ripples to dunes and ultimately to antidunes as the tractive force is increased. The physical relationships between form of bed roughness and the variables upon which form roughness depends are extremely complex. The independent variables are interrelated so that it is impossible to completely isolate the effect of a single independent variable on form roughness in a flume or stream. Important interrelated variables include: characteristics of bed material such as physical size, fall diameter and gradation; the temperature or fluid viscosity; the concentration of very fine sediment; and the depth as well as other flow variables. Methods of predicting forms of bed roughness from known characteristics of the flow and sediment are inexact, but as a first approximation, the bed roughness is related to stream power and median fall diameter of bed material. Different types of cross-bedding are associated with the various roughness elements, based on equilibrium flow conditions in recirculating flumes. The tendency for all flows to meander, even in straight channels, complicates both the forms of bed roughness and the types of cross-bedding. This tendency to meander is reinforced by the large bars which exist adjacent to one bank and then the other on the beds of alluvial channels. These bars may be of such small amplitude to go almost unnoticed in a given system, particularly when small width-depth ratios exist. However, if by reducing depth or by widening the channel the width-depth ratio is increased, these large bars may develop to almost the full depth of the channel. The regular forms of bed roughness are in general superposed on th se large bars, but the roughness forms change dramatically as the depth, velocity, and direction of flow change over the bar as deposition and development of the bars progress. End_of_Article - Last_Page 547------------

Control Structures for Sand-Bed Channels

Abstract: A laboratory study demonstrated the feasibility of constructing a relatively short channel to serve as a control structure to stabilize the depth-discharge relation in an alluvial sand channel. The large variations and discontinuities present in depth-discharge relations for alluvial sand channels resulting from scour and fill and changes in bed configuration are eliminated by this control. Such a structure also creates sufficient turbulence to suspend the bed material of the channel so that conventional suspended sediment samplers can be used to measure the total sediment discharge. The control was effective with a moderate amount of head loss, so that backwater effects and downstream erosion were minimal. The rock channel control should be more economical to construct than other concrete controls that are described. However, prototype studies are needed to develop the design specifications for the controls.