In the Midwest, the flood season runs from mid February to mid April. Heavy rains, melting snow, frozen ground and dormant trees combine to increase runoff and rivers, partly clogged by ice jams and flotsam, spill across their floodplains. This annual deluge, a recurrent nightmare for those who live along these waterways, once spawned vast wetlands and swamp forests; today, most of the floodplains have been cleared for crop fields and industrial ports.
Leaving swaths of shallow lakes, sloughs and flooded fields, this seasonal pattern coincides with the spring waterfowl migration, offering nutritious rest stops for the huge flocks of geese, ducks, coot and grebes that cross the Heartland on their way to northern breeding grounds. Migrant snow geese will be moving through in late February, followed by the Canada geese in early March; ducks peak in number and variety from mid March to early April.
As the weather warms in mid spring, the ice jams clear, the soil absorbs much of the moisture and the trees, festooned with new leaves, begin to transport much of the rainfall back to the atmosphere. Though stagnant weather patterns may produce regional flooding throughout the warmer months, the annual cycle is generally over by May.
