What to Expect
The Boise River is dam controlled, but can flood. Every few years the Boise River experiences flows that are higher than normal. They can cause minor flooding in low elevation areas near the river. In 2017, peak flows reached 9600 cubic feet per second (1 ft3 ≈ 1 basketball). Dam managers were days away from having to release more water from the dam and flood larger areas surrounding the river. Parts of the greenbelt were washed away and some homes near the river flooded.
During a worst-case scenario, major flooding would occur near the river in Boise, Garden City, Eagle, Star, and Caldwell. Some homes in low lying areas near the river would be flooded with water. Many city parks near the river, would be underwater. Debris piling up on bridge crossings will cause additional flood damage. The last flood of this magnitude on the Boise River happened in 1943. This was before the river was dam-controlled. (Source: National Weather Service)