Appendix 378.APPENDIX D

Ill. Admin. Code tit. 35, § 378.APPENDIX D

Manning Equation

AUTHORITY: Implementing and authorized by Sections 4, 11 and 39 of the Environmental Protection Act (Ill. Rev. Stat. 1987, ch. 111½, pars. 1004, 1011, and 1039).ENVIRONMENTAL PROTECTION AGENCY

V = 1.49 R_h^2/3 S^1/2

n

Q = 1.49 AR_h^2/3 S^1/2

n

where:	Q	is the discharge in cfs
	V	is the average velocity in fps.
	A	is the cross-sectional area of the stream in square feet.
	R_h	is the hydraulic radius of the stream in feet, as
		determined by the cross-sectional area (A) divided by the
		wetted perimeter.
	S	is the slope of the stream in decimal form.
	n	is the Manning coefficient.