Lab 2: Infiltration ESS 424: Environmental Stormwater Management Due Wednesday,
ID: 152830 • Letter: L
Question
Lab 2: Infiltration ESS 424: Environmental Stormwater Management Due Wednesday, September 12, 2018 by 3:35pm 1) I would like to install rain barrels to capture the rainfall at my new house. I have a typical two story home with approximately 1500 ft of roofing. How many 55-gallon rain barrels would I need to capture a 1 inch storm event assuming all runoff from the roof was captured (4pts to be split amongst a correct answer and properly shown work)? 2) Using the Kostiakov Lewis approach for infiltration estimation we may determine infiltration rate i in feet/min at a given time t in minutes though the following relationship i d +io For the cumulative version of the Kostiakov-Lewis infiltration estimation relationship we have Ikio t where I is in feet of water infiltrated, t is in minutes, a-e+1 and k d/a. For a silt loam soil and various land uses we have the coefficient values shown in the table below. For each land use, calculate the following (Ipt each): a) the infiltration rate (in iph) at each of those times for each land use (is andis) b) the total infiltration (in inches) after 5 minutes and 15 minutes (Is andlis 5 (iph) i15 (iph) 5 (in) 15 .00387 0.5421 0.006207 0.010416 0.4097 0.001215 are good dirt road 0.001808 0.638 0.0003149 3) Let us imagine that between 5 minutes and 15 minutes into a fictional storm our rainfall event gives us 0.3" of rain. Assuming: a) this is a sufficiently small time interval; b) we are at or above the infiltration capacity for the entire event; and c) there are no losses of the rain to wetting or to surface storage, calculate the depth of runoff (in inches) we will expect during that 10-minute time interval using the potential infiltration depth of the dirt road in question #2 (4pts to be split amongst a correct answer and properly shown work)?Explanation / Answer
1) Area of roofing = 1500 ft^2
Depth of water on the roof = 1 inch = 1/12 ft
Volume of water collected = ( 1500 ft^2 ) * ( 1/12 ft )= 125 ft^3
It is given 55 gallon rain barrels are there.
1 gallon = 0.133681 ft^3
55 gallons = 55 * 0.133681 ft^3 = 7.352455 ft^3
Number of 55 gallons barrels needed to capture the runoff = 125 ft^3 / 7.352455 ft^3
= 17.00112
As we have 17.00112 , let us round it to the next whole number.
So the Number of 55 gallons barrels needed to capture the runoff = 18
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