How do you calculate rainwater runoff?
To calculate the runoff from any given rainfall:
- Take the dimensions of the footprint of your roof and convert them to inches. (So, a 50′ x 20′ roof is 600″ x 240″.)
- Multiply the roof dimensions by the number of inches of rainfall. (In this example, 600″ x 240″ x 1″ = 144,000 cubic inches of water.)
How do you calculate rainwater harvesting?
Rooftop RWH potential is estimated by multiplying the average annual rainfall, roof area and runoff coefficient. Runoff coefficient of the concrete roof is considered in the calculation which typically varies from 0.70-0.80.
How is peak runoff calculated?
The Rational method predicts the peak runoff according to the formula: Q=CiA, where C is a runoff coefficient, i is the rainfall intensity, and A is the subcatchment area. This formula is applicable to US or metric evaluation, as long as consistent units are employed.
How is rainwater downpipe calculated?
For calculation we take the following formula: mean annual rainfall in mm x area in m² x runoff factor = collected rainwater in litres. In our example this means: 450 x 120 x 0.9 = 48 600 litres.
How is peak runoff rate calculated?
The Rational Formula is expressed as Q = CiA where: Q =Peak rate of runoff in cubic feet per second C =Runoff coefficient, an empirical coefficient representing a relationship between rainfall and runoff.
What is runoff formula?
The Rational Formula is expressed as Q = CiA where: Q =Peak rate of runoff in cubic feet per second C =Runoff coefficient, an empirical coefficient representing a relationship between rainfall and runoff. Step 2 Determine the runoff coefficient, C, for the type of soil/cover in the drainage area.
How is runoff ratio calculated?
Runoff ratio is the runoff for each watershed divided by the precipitation for that watershed. It is the proportion of rainfall that does not infiltrate and is not taken up by evapotranspiration, and thus ends up as runoff.
How do you calculate runoff factor?
Direct Runoff Formula For a given surface area such as a roof or yard, multiply the area by the inches of rainfall and divide by 231 to obtain the runoff in gallons. The factor 231 comes from the fact that the volume of 1 gallon equals 231 cubic inches.