Analysis of Partially Filled Circular Storm Sewers

by B. A. Christensen, Univ of Florida, Hydraulic Lab, Gainesville, FL, USA,

Document Type: Proceeding Paper

Part of: Water for Resource Development


The classic design approach uses Manning's formula. Comparisons between analytical results obtained in this manner and the many available experimental results indicate substantial depth discrepancies. In practice this problem has been overcome by introducing a variable Manning's n. Stricklers formula clearly indicates that Manning's n is a function of the roughness of the pipe. It does not appear logical to vary n with depth. By carrying out a Fourier analysis of available experimental data a relatively simple formula representing these data well is developed. Combined with the Darcy-Weisbach formula and Colebrook and White's expression for the friction factor this formula leads to an iterative method for determination of the normal depth. A calculator program in Reverse Polish Notation is presented for uniform flow. A similar program may be developed for backwater curves in partially filled pipes.

Subject Headings: Storm sewers | Stormwater management | Comparative studies | Hydraulic roughness | Uniform flow | Backwater | Curvature | Pipe flow

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