SOUTHEAST WISCONSIN -- On Wednesday, July 15 we roughly received a good soak of over 2" of rain across the greater Milwaukee area. Some spots received well over that but for argument sake, let's say we all got 2".
Another big assumption is the shape of Milwaukee. Obviously, it's not a perfect rectangle but to save time with math, let's assume it's an 18-mile by 10-mile area that covers the entire city.
Google Earth view of Milwaukee assuming we all got 2" of rain yesterday
Assuming those imaginary dimensions, we get an area of roughly 180 square miles. That's just about one-twentieth the size of Yellowstone National Park! Pretty big area but nothing too crazy.
Square mile area of Milwaukee assuming this fictional rectangle fills everywhere perfectly
We need to keep in mind we're not dealing with a 2D object anymore. If we've all gotten 2" of rain then we can easily calculate the area of our imaginary 3D object. First, we convert miles to feet and multiplying each length of our giant rectangular prism, we'll find that the area of water that covers the entire city of Milwaukee is roughly 836,318,546 Cubic Feet. Or in other words, roughly the same area as 9,500 Olympic sized swimming pools. How about them apples, Michael Phelps?
The volume of our rectangular prism can be calculated using this formula
You're probably starting to get the idea we're dealing with a lot of water. But water doesn't look like water in a rectangular object. What would the dimensions be if it was in a giant sphere?
We already have the area of water so it'll be easy to calculate the height of our sphere. Once finding the radius and multiplying by two, our initial rectangular prism of water is roughly equal to a giant sphere that is 1,168.92ft tall.
Calculate the height of our imaginary sphere based on the area we already calculated
The next question is how to visualize this. Looking at the skyline of Milwaukee, the tallest building is the US Bank Center that stands at 601ft tall. It's the tallest building in Wisconsin!
US Bank Center is roughly 601ft tall as seen from our Estabrook Camera
So if we know the height of one object we can compare that to our giant sphere and doing some simple division we know that our giant raindrop sphere is roughly 1.945 US Bank Centers tall.
Comparing that sphere to an object we know the height of it's roughly 1.945 US Bank Centers tall
And when we throw it all together the picture below is what 2" of rainfall from Wednesday looks like if it fell all at once over Milwaukee! Not as impressive as you might have thought. Keep in mind 3D objects have a lot of area inside compared to their 2D counterparts. But it's important to remember our infrastructure has to be able to handle that giant blob of water if we get 2" of rain.
That's why it's vital to unblock storm drains, wetland habitat to absorb the water into the soil, and reduce unnecessary runoff if possible.
What our giant sphere of water from 2" of rain would look like if it fell all at one time over downtown Milwaukee
Flood management is one of the hardest jobs the city has when keeping our lives and property safe. Calculating volume and overall impacts is a job if done right we never notice at all.
So next time you see a swollen river just understand the job it's doing in moving all that water so your basement doesn't flood!