How Much Runoff In Washington Roof

Runoff of course occurs during storms and much more water flows in rivers and as runoff during storms.

How much runoff in washington roof.

In the summer a green roof can typically retain between 70 80 of the run off in germany between 40 100 of rainfall can be retained dependent upon the season. Before you know what size rain barrels or cisterns to install you will need to calculate the average amount of rain runoff from your roof. Count the number of downspouts coming from your roof. Step 1 determine the footprint of your structure f in square feet.

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. Most areas in the region average less than two inches total rainfall for july and august. If your roof plan is more complicated break it up into smaller. Gallons of stormwater runoff from a one acre parking lot after one inch of rain.

Take the dimensions of the footprint of your roof and convert them to inches. Rainwater collection including the use of rain barrels has become more popular as a supplemental source of water. So a 50 x 20 roof is 600 x 240. You have to admit that whether you re in a drought situation or not it s hard to pass up that much of a free thing.

The puget sound averages about three feet of rain per year but two thirds of it falls from november to march. Nation s leading commercial producer of oysters clams and mussels. 75 of rain falling on extensive green roofs can be retained in the short term and up to 20 can be retained for up to 2 months. Measure along the length of the house or building and along the width of the house or building in feet.

Step 1 calculate the total area of your roof. The study plan can be found at the link below. If you get about 10 inches of rain over the course of the spring and summer an average 1 360 square foot roof would yield 8 160 gallons of rainwater. Gallons of stormwater runoff from a 1 200 square foot roof after one inch of rain.

In 2009 we issued a rainwater use interpretive policy which clarifies that you may use water collected from your rooftop without a water right permit however there are rules on using rainwater as a potable drinkable water source. To determine the amount of rain your roof catches multiply your home s width by its length in feet to estimate its footprint. For example in 2001 during a major storm at peachtree creek in atlanta georgia the amount of water that flowed in the river in one day was 7 percent of all the streamflow for the year. The answer is about 623 gallons.

Divide 100 by the number of downspouts in order to obtain the percentage of water collected from each downspout.