Residents in east Boise got an early start to their day on August 20, 1959 as loudspeakers on fire trucks gave warnings of a flash flood on Cottonwood Creek. Everyone escaped safely, but the stream filled basements with water and spread mud and debris.
Cottonwood Creek, which cheers runners in the “Race to Robie Creek” by watering trees along the route, has run amok on many occasions in Boise’s flood history. The last section of the stream now travels to the Boise River in underground pipes. But it has often foiled flood control plans since the town was founded. It last flooded in 1986.
Cottonwood Creek is most apt to flood during early thaws in January and February and after cloudbursts from May through August. In Boise’s early days the water ran up Main Street. On rare occasions, most of the downtown section was flooded with up to a foot of water, which could reach as far west as 16th Street.
All dams built on the creek in early days were no match for its terrifying flash floods. A flume was built to gather the water and direct it into a ditch but it washed out repeatedly. For years, travelers on Warm Springs Avenue and other east-west streets had to cross bridges over a ditch that carried the creek’s water to the river. One flood in the early 1920s was caused by an automobile that went off a bridge and landed in the ditch. Whether as the result of accidents or merely the doings of nature, Cottonwood Creek has kept Boiseans on their toes from pioneer days to the present.