Runoff Coefficient For Roof

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.

Runoff coefficient for roof.

On a low slope fully adhered epdm roof with slope of 1 4 per foot one could justify a coefficient of 95 to 99. Rational method runoff coefficients. The higher the value the greater the quantity of water which will need to be dealt with by the drainage system. 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. 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. The formula for calculating this flow is called the maming formula. 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 a larger value for areas with low infiltration and high runoff pavement steep gradient and lower for permeable well vegetated areas forest flat land. The runoff coefficient describes the percentage of rainfall which runs off a particular surface during a storm event. Tot per per tot imp impa a c a a.

And q the peak storm water runoff rate due to a storm of intensity i on. I the design rainfall intensity for a storm of specified recurrence interval and duration equal to the watershed time of concentration. Runoff coefficient c this coefficient allows for the quantity of water which runoff a particular type of surfacing into a drainage system and discount the quantity of water which will soak into or through the surfacing. Typical values are given below.

Step 1 determine the footprint of your structure f in square feet. 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. C v using datafit 9 1 32 model selection criteria. There are two ways you can find the runoff coefficient.

Why is it important. One of the parameters in the rational method equation q cia is the runoff coefficient c. 1 predicted c v must increase or remain constant for 0 p 100 mm 2 predicted c v 1 for 0 p 100. Rational method runoff coefficient applications.

The runoff coefficient c is a dimensionless coefficient relating the amount of runoff to the amount of precipitation received. Multiply the two figures together to obtain the square footage of your roof step 2 determine the percentage of water collected from each downspout p. A runoff coefficient is a number that relates the rainfall rate and runoff rate.