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Boulder Creek Flow Rates

Boulder Creek Flow Rates

The rate of flow of a creek, river or flood is measured by quantity over time. This is often referred to as the discharge, the rate at which a volume of water passes a specific point in a specific amount of time.

Under normal conditions, Boulder Creek typically flows at a rate between 100 and 300 cfs.

What does cfs mean? How much water is it?

Cfs stands for cubic feet per second, and is the most common unit used to measure the flow rates of Boulder Creek. One cubic foot per second is equal to the discharge through a rectangular cross section, one foot wide by one foot deep, flowing at an average velocity of one foot per second. This is equivalent to approximately 7.5 gallons of water per second.

Base Flow Rates

Boulder Creek typically has a low base flow (up to 300 cfs) between fall and late winter. Flow comes from snow-melt runoff, rainfall or groundwater. Water flows well within the creek banks and is typically flowing clear. Very low flow periods are supplemented with flow from Barker Reservoir to ensure adequate flow for aquatic habitats.

 

Boulder Creek Flow Rates In Cubic Feet Per Second (cfs)

Facing East

52

102

212

Facing West

52

102

212

Spring Flow Rates

Boulder Creek typically begins to flow higher during spring snow-melt runoff. Flows are well within the creek bank and typically do not exceed 500 cfs. The creek generally flows clear, but periods of turbid (cloudy) water can occur from excessive snow-melt runoff. Tubing and kayaking are allowed.

 

Boulder Creek Flow Rates In Cubic Feet Per Second (cfs)

Facing East

341

456

Facing West

341

456

Late Spring Flow Rates

In the late spring, Boulder Creek flows increase once Barker Reservoir fills and overflows. Creek flows can exceed 800 cfs, with a ban on tubing beginning at 700 cfs. Flow in the creek is typically bank full during late spring, is swift-flowing and typically turbid (cloudy) due to high runoff. It is not unusual for trail underpasses to be closed during late spring flows.

 

Boulder Creek Flow Rates In Cubic Feet Per Second (cfs)

Facing East

631

687

933

Facing West

631

687

933

High Flow Rates

The greatest chance for high flows in Boulder Creek occurs during periods of heavy rain. The greatest threat for heavy rain is typically during the summer months, but can also occur during late spring. The creek level can rise very quickly during heavy rain storms. The creek begins to overflow its banks and flood underpasses in many locations when flow exceeds 1,000 cfs. Extensive flooding will begin to occur when flows exceed 2,000 cfs. The 100-year event flow in Boulder Creek is estimated to be 12,000 cfs.

 

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