I the design rainfall intensity for a storm of specified recurrence interval and duration equal to the watershed time of concentration.
Runoff coefficient metal roof.
The system outlined below will walk you through the steps of determining your rain barrel sizes based on average roof runoff.
This makes the duration different for all the events as it is based on the actual duration of the event.
The runoff coefficient c is a dimensionless coefficient relating the amount of runoff to the amount of precipitation received.
One of the parameters in the rational method equation q cia is the runoff coefficient c.
We can observe that there is a significant reduction in storage capacity compared to the first scenario.
And q the peak storm water runoff rate due to a storm of intensity i on.
Use it to wash cars and outdoor equipment and to rinse patios.
Runoff generated roof area peak rainfall runoff coefficient 200 150 0 9 7100 gallons.
Rational method runoff coefficients.
For example it is 0 9 for metal or tile roofs and up to 0 3 for green roofs.
Unless the zinc content is particularly high it is safe to use on lawns and ornamental gardens.
A runoff coefficient is a number that relates the rainfall rate and runoff rate.
Roof runoff has many outdoor uses.
There are two ways you can find the runoff coefficient.
Runoff coefficients when calculating the amount of runoff that can be harvested from a roof it is common to include a runoff coefficient.
For sample purposes a 55 gallon barrel will be used.
This coefficient accounts for the fact that some roof surfaces are more efficient than others at collecting rainwater.
Assuming a peak possible rainfall of 150 mm over a 24 hour time period and the available roof catchment of 200 sq m the storage capacity will be.
The runoff coefficient value is an attempt to take account of the volume of runoff which is absorbed into the surface.
Precipitation and runoff data from each event were used to calculate the runoff coefficients for the roofs based on the same definition as in equation which means that the runoff coefficients for the field cases were calculated as the runoff volume over the total precipitation volume for the time span covered by the precipitation event.
For example a pitched metal roof is typically the most efficient.
The other parameters are a the area of a watershed.
Why is it important.
Alternatively the runoff coefficient is the factor by which depending on the type of surface the effective impermeable area is calculated.
One is by using the rational method and the other is by using a runoff coefficient.
This is not a very precise variable and as such attempts have been made to remove it using statistical analysis of historical events.
