Calculating Volume of a 2" Rainstorm Event

The dimensions of the Willet Science Center (WSC) parking lot was found to be 270 ft x 240 ft when measured by foot during lab. The distance measured using Google Earth (see picture below) was found to be 250 ft x 234 ft. The red lines highlight the length and width measurements. These distances are relatively close.

The amount of runoff was calculated using both sets of dimensions:
  
                           Runoff Total
   Dimensions        (gallons)
   By Foot:              82,400
   Google Earth:      74,390


The average swimming pool holds about 10,000 gallons of water. This means the runoff from a two inch storm event on the WSC parking lot could fill approximately 7-8 swimming pools.

It is necessary to perform runoff calculations so that storm water management systems can be designed to support the appropriate volume of water. If the system cannot handle the average rain event sized storm, then the parking lot and/or surrounding areas will flood often.