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With floods submerging expanses of the Midwest and government scientists warning that this spring could bring a historic flood season in the United States, it’s natural to ask why it is happening. What causes catastrophic flooding? And what is the role of climate change?

The first thing to understand: It’s complicated

Each flood is its own phenomenon, tied to the specific circumstances in the area.

“Flooding is complex,” Deke Arndt, a climate scientist at the National Oceanic and Atmospheric Administration , said Thursday in a briefing on the potentially dire flood season.

“It has to do with precipitation falling to the ground,” Mr. Arndt said, “but also with the way that water is managed and the surface hydrology — how it flows across the land and is collected and runs off.”

The question of water management involves the building and maintenance of dams, levees, reservoirs and spillways. The “surface hydrology” part is about the landscape and how it affects the flow of water (for example, places rich in steep hills and valleys like Vermont can see severe destruction from intense rain events). And the development of housing, malls and other paved-over areas reduces the amount of open land that can absorb runoff.