Runoff Coefficient For Roof

Rational method runoff coefficients.

Runoff coefficient for roof.

There are two ways you can find the runoff coefficient. Measure along the length of the house or building and along the width of the house or building in feet. The formula for calculating this flow is called the maming formula. And q the peak storm water runoff rate due to a storm of intensity i on.

Runoff coefficients paired rainfall p and observed runoff q obs from 21 living roofs volumetric runoff coefficient for each storm linear regression for paired p. It is a larger value for areas with low infiltration and high runoff pavement steep gradient and lower for permeable well vegetated areas forest flat land. Why is it important. Annual runoff generated roof area annual rainfall runoff coefficient 200 1000 0 9 180 000 litres or 47 520 gallons hence a storage capacity of 47 520 gallons is required to sail through the summer months with adequate water supply.

C v using datafit 9 1 32 model selection criteria. Tot per per tot imp impa a c a a. On a low slope fully adhered epdm roof with slope of 1 4 per foot one could justify a coefficient of 95 to 99. Divide 100 by the number of downspouts in order to obtain the percentage of water collected from each downspout.

Typical values are given below. 1 predicted c v must increase or remain constant for 0 p 100 mm 2 predicted c v 1 for 0 p 100. The higher the value the greater the quantity of water which will need to be dealt with by the drainage system. A runoff coefficient is a number that relates the rainfall rate and runoff rate.

Step 1 determine the footprint of your structure f in square feet. Rational method runoff coefficient applications. The american society of plumbing engineers data book suggests that initially there will be some friction along the drainage path but it will quickly go to zero. Count the number of downspouts coming from your roof.

The rational method considers a runoff coefficient of about 0 7 0 95 for both concrete streets and roofs the most impervious and a runoff coefficient of about 0 05 0 35 for lawns areas the most pervious. One of the parameters in the rational method equation q cia is the runoff coefficient c. The runoff coefficient describes the percentage of rainfall which runs off a particular surface during a storm event. The runoff coefficient c is a dimensionless coefficient relating the amount of runoff to the amount of precipitation received.

Using the runoff coefficient scientists and hydrologists can calculate how much water passes over a given area per second. The other parameters are a the area of a watershed. It is possible to calculate the average runoff coefficient for non homogeneous areas considering.