Cottonwood Creek Lower dam
Cottonwood Creek Lower
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.
Dam data reference
Condition Assessment
- Satisfactory
- No existing or potential dam safety deficiencies are recognized. Acceptable performance is expected under all loading conditions (static, hydrologic, seismic) in accordance with the minimum applicable state or federal regulatory criteria or tolerable risk guidelines.
- Fair
- No existing dam safety deficiencies are recognized for normal operating conditions. Rare or extreme hydrologic and/or seismic events may result in a dam safety deficiency. Risk may be in the range to take further action.
- Poor
- A dam safety deficiency is recognized for normal operating conditions which may realistically occur. Remedial action is necessary. POOR may also be used when uncertainties exist as to critical analysis parameters which identify a potential dam safety deficiency.
- Unsatisfactory
- A dam safety deficiency is recognized that requires immediate or emergency remedial action for problem resolution.
- Not Rated
- The dam has not been inspected, is not under state or federal jurisdiction, or has been inspected but, for whatever reason, has not been rated.
Hazard Potential Classification
- High
- Dams assigned the high hazard potential classification are those where failure or mis-operation will probably cause loss of human life.
- Significant
- Dams assigned the significant hazard potential classification are those dams where failure or mis-operation results in no probable loss of human life but can cause economic loss, environmental damage, disruption of lifeline facilities, or impact other concerns. Significant hazard potential classification dams are often located in predominantly rural or agricultural areas but could be in areas with population and significant infrastructure.
- Low
- Dams assigned the low hazard potential classification are those where failure or mis-operation results in no probable loss of human life and low economic and/or environmental losses. Losses are principally limited to the owner's property.
- Undetermined
- Dams for which a downstream hazard potential has not been designated or is not provided.
Plan around the weather
Same NOAA / yr.no feed Snoflo's iOS app uses. Watch the precipitation column on the meteogram -- rain on the basin upstream typically lifts inflow 24-72 hours later.
Next 5 days, hour by hour
Temperature line with weather symbols on top, snow + rain accumulation as columns, humidity as a dotted line.
5-day forecast table
Every 3 hours, broken out across temperature, snow, rain, humidity, and wind. Each cell is colour-coded relative to the column min/max.
| Time | Condition | Temp (°F) | Snow (in) | Rain (in) | Humidity (%) | Wind (mps) | Wind dir |
|---|---|---|---|---|---|---|---|
| Loading detailed forecast… | |||||||
15-day temperature & precipitation
Daily temperatures, snow, and rain projected over the next two weeks.
Nearby streamflow gauges
USGS streamgauges around Cottonwood Creek Lower -- inflows here typically show up in storage 24-72 hours later.
| Streamgauge | Discharge | View |
|---|---|---|
| Cottonwood Creek Bel Fivemile Cr Nr Boise Id | 1 cfs | → |
| Boise River At Glenwood Bridge Nr Boise Id | 1,760 cfs | → |
| Boise River South Channel At Eagle Id | 1,120 cfs | → |
| Dry Creek Nr Eagle Id | 0 cfs | → |
| Eagle Drain At Eagle | 44 cfs | → |
| Mores Creek Ab Robie Creek Nr Arrowrock Dam Id | 227 cfs | → |
Make a day of it
Boat launches, lakeside camping, fishing access, and other reservoirs near Cottonwood Creek Lower.
Boat launches
- Robie Creek Road Boise County
- Parnell Recreation Site
- Upper Embankment Road Canyon County
- Look Lane 21723, Canyon County
- Beehive Bend
Campgrounds
- Gowen Field Military
- Macks Creek
- Shafer Butte Cg And Group Sites - Reserve - Tent
- Shafer Butte
- Arrowrock Reservoir Dispersed
- Indian Creek Reservoir
Paddle runs
- Boise Nf Boundary To Confluence With Willow Creek
- Trail Creek To Confluence With Crank Creek
- Confluence With Granite Creek To Confluence With Pine Creek
- Confluence With Rabbit Creek To Confluence With Middle Fork Boise River
- Mennecke Creek To Confluence With Trail Creek
- Boise Nf Boundary (1 Mile East Of Banks) To Boise Nf Boundary (1 Mile South Of Banks)
Track Cottonwood Creek Lower in the Snoflo app
Save this dam as a favorite and get the local NOAA / yr.no forecast plus regional flow context wherever you are.
About Cottonwood Creek Lower
Where does the data for Cottonwood Creek Lower come from?
Structural and regulatory data come from the U.S. Army Corps of Engineers' National Inventory of Dams (NID). Weather forecast comes from NOAA / yr.no -- the same feed Snoflo's iOS app uses.
How often is the report updated?
NID structural data refreshes annually as the Corps publishes updated assessments. The weather forecast refreshes throughout the day.
What does the Significant hazard rating mean?
The Corps of Engineers' hazard potential classification grades probable consequences if the dam fails: High = probable loss of human life; Significant = no probable loss of human life but possible economic loss / environmental damage; Low = no probable loss of human life, only minor economic / environmental losses. See the Dam Data Reference card above for the full definitions.
What's "% of normal"?
The current storage value compared to the historical average storage on this calendar day. 100% = right on average; values above 100% mean above-normal storage (wet year); values below mean below-normal (dry year or drought).
Can I get alerts when storage crosses a threshold?
Yes -- alerts are managed in the Snoflo iOS app. Favorite this dam, set a threshold, and you'll get a push the moment conditions cross.
Other water bodies near here
Snoflo-tracked reservoirs and dams within driving distance of Cottonwood Creek Lower.