How Is Runoff Calculated?

What is design storm?

In summary, Design Storm is hyetograph, or time distribution, of the design rainfall over a specific duration.

The term design storm is used to refer to a rainfall hyetograph that is believed to have the characteristics that are critical to the safety of the project..

Where does stormwater runoff go?

Most Stormwater Runoff flows either: directly into streams, rivers, ponds, lakes and wetlands or down the nearest Storm Drain and then into the nearest waterway without any treatment.

How much water will my roof catch?

To calculate how much rainwater can be harvested, multiply your rainfall (mm) by your roof surface area (m2) being used to catch rainwater. The resulting number represents how many litres of water you can expect to collect.

What is the process of runoff?

Runoff occurs when there is more water than land can absorb. The excess liquid flows across the surface of the land and into nearby creeks, streams, or ponds. Runoff can come from both natural processes and human activity. … Runoff also occurs naturally as soil is eroded and carried to various bodies of water.

What is the difference between runoff and discharge?

Thus, the terms discharge, streamflow, and runoff represent water with the solids dissolved in it and the sediment mixed with it. Of these terms, discharge is the most comprehensive. … The differentiation between runoff as a volume and streamflow as a rate is not accepted.

What is total runoff?

The total runoff is equal to the total precipitation less the losses caused by evapotranspiration (loss to the atmosphere from soil surfaces and plant leaves), storage (as in temporary ponds), and other such abstractions.

How do you calculate rainwater flow rate?

Q = C x I x A/96.23, where,Q is the storm-water run-off in gallons per minute (GPM)C is the runoff coefficient,I is the rainfall intensity in inches per hour.A is the drainage area in sq. ft.23 is a conversion factor when you want the flow rate in GPM and your drainage area is in sq. ft.

How do I divert my stormwater runoff?

shovelsDig a Swale. A swale is a shallow trench that redirects water to where it can be safely released. … Construct a Dry Stream. Like swales, dry streams redirect water and prevent runoff damage. … Grow A Rain Garden. … Build a Berm. … Route Water Into a Dry Well. … Lay Pervious Paving.

How is peak runoff rate 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.

What is runoff coefficient?

The runoff coefficient (C) is a dimensionless coefficient relating the amount of runoff to the amount of precipitation received. 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).

How do you calculate water drainage?

To do this, we simply multiply across each row. The runoff, Q, for the roof area in drainage Zone A is: (1.00 x 1.5 x 500) / 96.23 = 7.79 gallons per minute. The runoff for the grass portion of drainage Zone A is: (0.35 x 1.5 x 900) / 96.23 = 4.91 gpm.

Is runoff good or bad?

Runoff from agricultural land (and even our own yards) can carry excess nutrients, such as nitrogen and phosphorus into streams, lakes, and groundwater supplies. These excess nutrients have the potential to degrade water quality.

How is roof runoff calculated?

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. … Divide by 231 to get the number of gallons (because 1 gallon = 231 cubic inches).