Velocity and Discharge Capacity of a Rectangular Open Drain

In this post, we determined the velocity of fluid passing through a rectangular open drain  by using Manning’s formula;                                                                                                         

V             =             RH ^2/3 *So^1/2 / n                

Here;                    

V            =             Velocity in m/sec                                                                              

So           =             Channel bed slope in fraction                                                    

RH          =             Hydraulic radius = Cross sectional area of channel / Wetted parameter                  

n             =             Roughness coefficient                                                                                                                                                  

We further calculate discharge by using  volumetric  flow rate

Discharge capacity of rectangular open drain in m³/sec                   QD          =             A ×  V  

Adequacy Check

you can also check the adequacy of the drain section by comparing the calculated “Discharge capacity of the rectangular open drain” to the rainwater runoff calculated in the previous post  “https://knowledgesharingplatform.com/calculation-of-storm-water-runoff”, if Discharge capacity of the rectangular open drain is greater than the rainwater runoff then drain section is adequate.