How Much Runoff In Washington Roof

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.

How much runoff in washington roof. The puget sound averages about three feet of rain per year but two thirds of it falls from november to march. Step 1 determine the footprint of your structure f in square feet. Most areas in the region average less than two inches total rainfall for july and august. 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.

Take the dimensions of the footprint of your roof and convert them to inches. Gallons of stormwater runoff from a 1 200 square foot roof after one inch of rain. 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. To determine the amount of rain your roof catches multiply your home s width by its length in feet to estimate its footprint.

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. For a rectangular house this is simply done by multiplying the length by the width of the roof. The answer is about 623 gallons. If your roof plan is more complicated break it up into smaller.

Rainwater collection including the use of rain barrels has become more popular as a supplemental source of water. Count the number of downspouts coming from your roof. Gallons of stormwater runoff from a one acre parking lot after one inch of rain. Nation s leading commercial producer of oysters clams and mussels.

Measure along the length of the house or building and along the width of the house or building in feet. 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. Divide 100 by the number of downspouts in order to obtain the percentage of water collected from each downspout. Step 1 calculate the total area of your 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. The study plan can be found at the link below. To calculate the runoff from any given rainfall.

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