Backflow

Cities plan their drains with flood simulations. Some settings in those simulations cannot be measured, so engineers guess them. Checking the guesses normally needs water sensors underground, which almost nobody has. Backflow checks and corrects a flood simulation using only video. We used a real flood test site in Switzerland (the FloodX dataset), which is filmed from several cameras. Gemini 4 Argon read the site's engineering drawing and built the whole site in 3D. It noticed a drain was missing from its own scene and fixed its own code. The simulation (EPA SWMM) makes three versions of the flood. We draw each one in Argon's 3D site, from the real camera's angle, next to the real footage. Argon watches the whole flood, picks the closest version, and says what is still wrong. The settings move toward its pick, and the loop repeats. Then we freeze the model and test it on a different flood it has never seen, and only then compare it with the real water sensors. After watching one flood, the prediction was more than five times more accurate. That is in the range researchers reach when they tune with sensors.