UNITED STATES DEPARTMENT OF AGRICULTURE 



•iv^lMka. 



Contribution from the Bureau of Public Roads 

 THOS. H. MACDONALD, Chief 



Washington, D. C. 



PROFESSIONAL PAPER 



June 7, 1920 



THE FLOW OF WATER IN DREDGED DRAINAGE 



THE RESULTS OF EXPERIMENTS TO DETERMINE THE ROUGHNESS 

 COEFFICIENT, n, IN KUTTER'S FORMULA. 



By C. E. Ramser, Senior Drainage Engineer. 



CONTENTS. 



Page. 



Introduction 1 



Field measurements 2 



Computations 4 



Tabulated results 6 



Description of channels 7 



Accuracy of results 9 



Description of experiments 9 



Experiments in Lee County, Miss 9 



Experiments in Bolivar County, Miss ... 17 



Page. 



Description of experiments — Continued. 



Experiments in western Tennessee 24 



Experiments in western Iowa 36 



Experiments in North Carolina 45 



Experiments in Florida 51 



Variation of n with stage 58 



Application of results 58 



Conclusions 59 



INTRODUCTION. 



Kutter's formula is generally accepted by engineers as being the 

 most satisfactory formula in use for computing the flow of water in 

 open channels. After a thorough and unbiased study of all known 

 formulas for computing the flow in open channels, engineers of the 

 Miami Conservancy District conclude that " Although the Kutter 

 formula is not ideal it is the best equation available at the present 

 time." * The results obtained by the use of this formula are, how- 

 ever, affected to such a degree by the coefficient of roughness, n, that 

 the selection of the correct value for this factor is a matter of the 

 highest importance. The series of experiments described and sum- 

 marized in the following pages were made for the purpose of deter- 

 mining just what values of n properly apply to the various conditions 

 of channel, and the endeavor has been made to present this informa- 

 tion in the form that will be of the most practical value to engineers 

 charged with the design of drainage channels or the computation of 

 the discharge capacity of existing channels. 



1 The Maimi Conservancy District, Technical Reports, Part IV. 

 Channels," by Ivan E. Houk, Assoc. M. Am. Soc. C. E. 

 14G90S°— 20— Bull. 832 1 



"Calculation of Flow in Open 



