The Mathematics of a Resiliency Park- Does Holding 400,000 Gallons of Water Impact the Flooding Impact of 17,400,000 Gallons of Water?

Real world application of mathematics and science are consistent with national STEM reform efforts. Such skills also are consistent with better informed citizens who are often asked to participate in critical infrastructure efforts. 

One current example involves the chronic flooding in Hoboken, NJ. Some will recall, Hoboken was severely impacted by Superstorm Sandy and still floods often and regularly. 

The city has implemented a number of efforts over the year (water gardens for example). One effort is the notion of a resiliency park where rainwater would be retained in large underground containers during heavy rain events. Will these efforts be effective? One way to look at this question is via mathematics and science rather than by public relation campaigns. 

Here is how a middle to high school problem may be posed centering around a problem which attempts to mitigate flooding. 

Question: A new park in a city will include underground infrastructure to withhold 400,000+ gallons of rain to reduce flooding. If the town is one square mile, how significant is this infrastructure in reducing the chance of flooding?

Note: The amount of rain considered to be capable of flooding is roughly in an hour can vary depending on the location and the type of precipitation. However, generally, rainfall rates of 1 inch (2.54 centimeters) or more per hour are considered heavy or intense, and may cause flash flooding and other hazards

Mathematical Calculation: A rainfall of 1 inch over square mile is equal to 17,400,000 gallons of water. A resiliency park capable of holding 400,000 gallons of water would represent 2.29% of the rainfall that falls during a 1 inch rainfall

Answer: Please assess the relative effectiveness of this resiliency park. 

Additional Information: https://www.tapinto.net/towns/hoboken/sections/green/articles/have-your-say-hoboken-residents-invited-to-take-800-monroe-resiliency-park-survey

https://patch.com/new-jersey/hoboken/no-pool-you-can-still-choose-plan-800-monroe-st-hoboken