Cottonwood Creek Lower, also known as Military Reserve Flood Basin #3, is a vital flood risk reduction structure located in Boise, Idaho. Constructed in 1961 by Morrison Knudsen Corp, this earth dam with a stone core stands at a height of 15.4 feet and has a hydraulic height of 10.4 feet. With a storage capacity of 88 acre-feet, this structure serves to protect the surrounding area from potential flooding events along Cottonwood Creek and the Boise River.

Managed by the Idaho Department of Water Resources, Cottonwood Creek Lower is subject to regular state inspections and enforcement to ensure its operational readiness. The dam has a spillway width of 280 feet and can handle a maximum discharge of 3540 cubic feet per second. While the structure's hazard potential is deemed significant, its overall condition assessment is fair as of the most recent inspection in September 2018. The surrounding community benefits from this flood control measure, which plays a crucial role in mitigating flood risks in the region.

Given its strategic location and importance in flood risk reduction, Cottonwood Creek Lower serves as a key asset in the water resource management infrastructure of Ada County, Idaho. With its proximity to the Boise River and its effective storage capacity, this dam plays a significant role in protecting the local community from potential inundation events. As climate change continues to impact precipitation patterns and increase the frequency of extreme weather events, structures like Cottonwood Creek Lower are essential in safeguarding both lives and property from the dangers of flooding.