Authorities used boats and large vehicles on Saturday to rescue and evacuate residents in parts of the Midwest where a recent deluge of rainwater and snowmelt poured over frozen ground, overwhelming creeks and rivers and killing at least one person. Evacuation efforts in eastern Nebraska and some spots in western Iowa on Saturday were hampered by reports of levee breaches and washouts of bridges and roads. The flooding followed days of snow and rain — record-setting, in some places — that swept through the West and Midwest. The deluge pushed some waterways, including the Missouri River, to record levels in Nebraska, South Dakota, Iowa and Minnesota. The flooding was the worst in nearly a decade in places.