Calculating Storm Water Runoff Pervious vs. Impervious Materials

How much is in the downspout?

Issues with Impervious Surfaces Increased volume of water Increased velocity of water Increased contaminant levels Increased water temperature in warm months

Stream bank erosion

How many gallons of water would be needed to cover the floor of the classroom with water to a depth of 1 in.? One inch of rain falling on one square foot = _______ gal. or _______ gal. / ft General dimensions of classroom: Length = ________ ft. Width = __________ ft. Area of classroom = Length __ ft. X Width __ ft. Amount of water needed: ______ sq. ft. X 0.63 gal. / ft. = ________ gal.

Before Development (example) Mostly Pervious Surface

Winburn School Grounds Much Impervious Surface

Boundaries

1 in. of rain falling on 1 acre of ground = 27,154 gallons of water ___ acres of school property X 27,154 gal./acre = _______ gallons13353,002 ___ acres of roof surface X 27,154 gal./acre = _________ gallons2.259,739 ____ acres of paved surface X 27,154 gal./acre = _______ gallons1.848,877