The map now began to fluctuate in a way that at first was visually jarring and difficult to follow. But as time went by Saskia understood that this was a collage that someone had assembled from aerial imagery. It was a mixture of satellite and drone photography showing the "reservoir" and its environs as they had actually looked over the last few decades. Early on, the coverage was spotty—they only had images at intervals of weeks or months, so the change from one to the next was jarring—but soon enough (as years went by and satellite coverage became ubiquitous) it smoothed out to the point where you could watch it like a movie. And what the movie showed was the reservoir throbbing like a living thing, an organic blob under a biologist’s microscope. Sometimes it shrank to nothing and all you saw was trees. But then in the aftermath of a heavy rain it would form puddles in the low places that would grow explosively over a few hours or days to fill the neat boundaries circumscribed by the levees. Every so often it would break out and become an even larger body of water with houses projecting from its surface. As years went by, some of those houses disappeared. T.R. wanted them to notice that. He led the swarm toward the edge of one such neighborhood and let them see how a swath of homes had been lost to the floodwaters of Hurricane Harvey. "A hundred and twenty-five billion," T.R. said. "That was the price tag for Harvey. Second only to Katrina, which was a hundred and sixty-one. So that’s what kind of money we’re talking. Damages on the order of one or two hundred billion, inflicted on this city suddenly and at unpredictable times."