Hurricane Harvey has already broken the record for the most rainfall from a single storm in the continental United States, even as its diminished remnants move on to drench Louisiana. The most rain recorded in a single place during the storm was an astonishing 51.88 inches in Cedar Bayou, Tex. — just shy of the 52-inch U.S. record for rainfall set in tropical Hawaii.
What does 51.88 inches of rain look like? Something like this:
It’s a huge amount of water that fell across a remarkably wide area. As a meteorologist with Harris County, Tex., noted on Twitter, enough rain fell in Houston to sink the entire county under 33 inches of water. That’s almost what happened, too, given Harris County’s broad and flat contours.
That amount of rain has been tough to visualize. To that end, we’ve created a tool that imagines a 51.88-inch deluge drenching a number of points in a circle around where you live (or anywhere else) and visualizing what the effect would be: where in that circle the water would pool and how deep it would get. (For our purposes, we’re imagining each point to receive 51.88 inches over a square yard of surface.)
Here’s the tool, with an explanation to follow.
Let’s look at the Penn Hills neighborhood near Pittsburgh, an appropriately hilly one. (Try entering “15235” on the tool.) There, the deluge would pool in a number of lower-lying areas.
How deep would it get? Again imagining that the water is constrained to this circle, it would get nearly 18 feet deep in the southwestern part of that region.
In effect, then, this shows us generally how any neighborhood might be affected — where the flooding would be worst and how bad it could get. It’s a rough visualization but one that clearly shows how disparate the effects of a heavy storm can be.
In reality, of course, the water would continue to drain downward, along the paths of those streams and rivers. Which brings us back to Houston.
Here’s a random point in the city:
Houston is much flatter than Pittsburgh, and the water barely pools anywhere. This is part of the current problem: Drainage is much slower.
There’s no way in which this tool can fully capture the scale of what’s happening on the Gulf Coast. What it can do, we hope, is give a sense of how dire the same situation might be in a context with which you might be more familiar.
Thanks to Mapzen for help creating this tool.