Investigating the Relationship between the Manning Coefficients (n) of a Perforated Subsurface Stormwater Drainage Pipe and the Hydraulic Parameters

Subsurface perforated pipes drain infiltrated stormwater runoff while attenuating the peak flow. The Manning roughness coefficient (n) was identified as a fundamental parameter for estimating in various subsurface channels. Hence, this work, performance of six-row non-staggered sand-slot pipe sample drainage is investigated experimentally laboratory flume at Universiti Sains Malaysia (USM) aimed determining coefficients and assessing relationship between Manning’s n hydraulic parameters simulated flow under conditions tailgate channel being opened fully (GFO) partially (GPO), well having longitudinal slopes 1:750 1:1000. Water pumped into maximum discharge rate 35 L/s, velocity depth are measured nine points along inner parts pipe. Based on calculated Reynolds numbers ranging from 38,252 to 64,801 both GFO GPO conditions, it determined that most turbulent, discharges velocities outlets higher than rates with similar range 0.004 0.009. ranges n, an inverse linear relationships observed R2 0.975 0.966, 0.819 0.992 resulting predicting values equations v = ((0.01440 − n)/0.009175), ((0.01330 n)/0.00890), ((0.02007 n)/0.01814), ((0.01702 n)/0.01456) 1:1000, respectively. It concluded since (Manning’s n) increases, able reduce pipe, lower ability control quantity storm water urban drainages.