Sim Society: DARPA, serious simulation, and the model that stopped a flood

The science of prediction has a long history of seeking answers to seemingly impossible questions. What will the weather look like next month? Will the stock market dip in the next hour? In 1928, studies were being done by the United States government to find an answer to another hard question, one that might save lives: Can you predict the nature of a river before a flood?

A year before, across Midwest America, spring started when the snowpacks from the previous winter began to melt and run down into the Mississippi river. Unlike previous years, the change in season was met with an unexpected rain. It rained through the start of January, and continued for the entire month, slowly filling the Mississippi, which rose little by little. By February the levees around the river were starting to strain with the rising water. Three months later, a whopping 145 levees around the Mississippi failed and 10 states were underwater. The flood would span 27,000 square miles and leave over a thousand dead.

In an episode titled America's Last Top Model, tha podcast 99% Invisible tracks the multi-decade-long development of one answer to the question of what a river might do in the face of unprecedented rain. The Mississippi River Basin Model is a physical reconstruction of the whole Mississippi river, designed to a 1/2000 scale. Imagine! 1.25 million square miles shrunk down to 200 acres of land. The model was so sprawling it could only be viewed in full if you climbed up to the top of an observation platform four storeys high. Yet it was small enough that in photographs taken during its construction, the compact man-made river makes its inspectors look mammoth by comparison; they lean over the model levees like inquisitive giants.

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