TABLE OF CONTENTS Manning's formula, published in 1890, gives the value of c in the Chezy formula as
The complete Manning formula being
and combining with the Chezy equation
| where A = | cross-sectional area of flow in square feet |
| S = | slope, or grade, in ft/ft |
| R = | hydraulic radius, feet |
| n = | coefficient of roughness |
In many computations, it is convenient to group the properties peculiar to the cross section in one term called conveyance (K)or
Then
Uniform flow of clean water in a straight, unobstructed channel would be a simple problem but is rarely attained. Manning's formula gives reliable results if the channel cross section, roughness, and slope are fairly constant over a sufficient distance to establish uniform flow.
This subsection courtesy of American Iron and Steel Institute.
| 1. | Fairly regular section: | |
| a. Some grass and weeds, little or no brush | 0.030 0.035 | |
| b. Dense growth of weeds, depth of flow materially greater than weed height. | 0.035 0.05 | |
| c. Some weeds, light brush on banks | 0.035 0.05 | |
| d. Some weeds, heavy brush on banks | 0.05 0.07 | |
| e. Some weeds, dense willows on banks | 0.06 0.08 | |
| f. For trees within channel, with branches... |
