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Boulder Creek Flow Rates

Boulder Creek Flow Rates

The flow rate 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 cubic feet per second (cfs).

Current Flow Rates

Boulder Creek Camera

What does cfs mean? How much water is it?

Cubic feet per second (cfs) is the most common unit used to measure the flow rates of creeks, rivers and floods. 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 snowmelt 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 Base Flow Rates In Cubic Feet Per Second (cfs)

52

102

212

Spring Flow Rates

Boulder Creek typically begins to flow higher during spring snowmelt runoff. Flows are 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 snowmelt runoff. Tubing, rafting and kayaking are allowed.

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

341

456

Late Spring Flow Rates

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

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

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 flooding can occur at any time. 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. More extensive flooding will begin to occur when flows exceed 2,000 cfs. The 100-year flood along Boulder Creek is estimated to produce flow rates of about 12,000 cfs.

Predicted Flow Rates for Boulder Creek at Broadway

Flood Event Peak Flow
10-year 2,200 cfs
25-year 5,580 cfs
50-year 8,000 cfs
100-year 12,000 cfs
500-year 21,800 cfs

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