Question

7. Of the following cover types, which do you expect to have the highest curve number? a) Woods b) Urban districts c) Meadow d) Golf Course

Answer 1

Curve number method is that in which we do not measure the no run off is measured , this method is used to estimate the depth of direct runoff from the rainfall depth . I am going to explain the entire concept because as per the guidelines we have to submit the detailed answers . This method practically works on two states that is :

• Initial accumulation of rainfall  
• After runoff

FORMULA USED FOR CALCULATIONS :

=> F/S = Q / ( P - Ia )

In this , F => Actual Retention (mm)

S => Potential Maximum Retention

P => Accumulated Rainfall Depth

Q => Accumulated Runoff Depth
Ia => Initial Abstraction

ESTIMATING THE CURVE NUMBER :

FIRST < 1% Flat

SECOND 1 - 5% Slightly sloping

THIRD    5 -10% Highly sloping

FOURTH 10 - 20% Steep

FIFTH > 20% Very steep

These runoff number indicates runoff potential , if the curve number is low it states that the soil is more permeable . These number ranges from 30 to 100

FOR WOODS THE CURVE NUMBER IS : 30 - 77

FOR URBAN DISTRICTS THE CURVE NUMBER IS : 81 - 95

FOR MEADOW THE CURVE NUMBER IS : 30 - 78

FOR GOLF COURSE THE CURVE NUMBER IS : 39 - 89

THE HIGHEST CURVE NUMBER IS FOR URBAN DISTRICTS AS I HAVE STATED ABOVE . I HAVE PROVIDE A DETAILED NOTE ON HOW WE CALCULATE AND HOW ESTIMATING THE CURVE VALUE .

HOPE SO YOU WOULD APPRECIATE MY EFFORTS , PLEASE PROVIDE POSITIVE RATINGS . THANK YOU