The Surprisingly Solid Mathematical Case of the Tin Foil Hat Gun Prepper

Or, “Who Needs an AR-15 Anyway?”
BJ Campbell
Apr 20, 2018 · 11 min read

As gun policy discussions unfold in the wake of mass shooter incidents, they routinely end in three buckets. There’s the “tyranny can never happen here” bucket, which the left has mostly abdicated in the wake of Trump winning after they called (and still call) him a tyrant. There’s the “you can’t fight the army with small arms” bucket, which is increasingly unsound given our ongoing decade-and-a-half war with Afghani tribal goat herders. And there’s the “what the hell do you need an AR-15 for anyway?” bucket, which, by its very language, eschews a fundamental lack of understanding of what those people are thinking. I am not a prepper. But I know a few. Some of the ones I do know are smart. They may not be doing as deep an analysis as I present here, on a mathematical level, but the smart ones are definitely doing it at a subconscious level. If you want to understand the perspectives of others, as everyone in my opinion should strive to do, then you would do well to read to the end of this article. To get where we’re going, we will need to discuss the general framework of disaster mathematics.

Stormwater Hydrology and the Mathematics of Unlikely Events

I’m not a writer by trade. I’m a stormwater hydrologist, and in my opinion, a pretty good one. Hydrology is the science of tracking water as it moves through the water cycle, from ocean evaporation through cloud formation, precipitation, groundwater infiltration, runoff, evapotranspiration, riverine hydraulics, and the time series behavior of reservoirs. It is a deep and fascinating field, but one of its most relevant applications to our lives is delineating floodplain boundaries.

To determine a floodplain boundary, we first identify a “storm event” that concerns us. We use historical rainfall data and some statistical magic to calculate the worst storm event a place is likely to experience in a 100-year time span, probabilistically speaking, and we call that the “100-year storm.” There’s a push in the field to quit calling it that, because it confuses the muggles, so now we often say something like “the storm which has a 1% chance of happening in any given year.” Then we take that rainfall data, judiciously apply more math, and turn it into a flow rate in a river. Then we do hydraulics (more math) to determine how deep the river will have to be to carry that much water, and we draw a line on a map.-- excerpt, rest at link above --

Fun and interesting read.

This looks much more interesting than the sad closing bars of today's "hearing!"