85 you will get 1.7 ft/s, this will most likely be a better value to use in your flow calculation for the overall discharge rate. For example, if your surface velocity measurement is 2 ft/s (feet per second) and you multiply that by. 85, to adjust the overall velocity to be more representative of the slower velocities under the surface. To account for this, we take the surface velocity measured, and multiply it by. NOTE: Surface velocities are typically higher than average overall channel velocity. New Estimated CFS вЂ“ 4.86 Area x 1.87 ft/s = 9.136 CFS 85 = 1.87 adjusted ft/s (feet per second) If my float measurements gave me an average surface velocity of 2.2 ft/s (feet per second), then I can calculate the CFS discharge by using the discharge formula below.Д¬FS = 10.69 (Cubic Feet per Second) or CFS x 448.83 = 4,797.99 GPM (converted CFS to GPM)ДЄdjusted Velocity (see note below) = 2.2 ft/s x. Now you can take the channel width (letвЂ™s say 6 feet) and multiply that by the average depth. 81 вЂ“ this is the average depth across the channel.

See example below: Depth 1ДЄdd up the depth values to get 8.1 and divide that by the number 10 (10 is how many measurements were made) the value you get is. Try to take these depth readings about every 1 foot across (depending on the width and uniformity of the channel).ДЄfter taking the depth readings you simply add up the depths and divide that number by how many depth readings you measured. To get an overall channel area measurement, simply measure the width of the channel and then take 10 or more depth readings across the width. Taking ten depth measurements is the recommended minimum required but more will be better, especially in larger channels (about every foot across). Use a yard stick or staff gauge to measure the depth at regular intervals across the channel. Be sure it is safe to wade, before getting in the channel. Measure streamвЂ™s width and depth across the downstream marker section. You should repeat the measurement at least 3 times and use the average feet per second by adding the three measurements and dividing that number by 3. Start the timer when the object crosses the upstream marker and stop the timer when it crosses the downstream marker. Step 3.В Throw your floating object into the stream upstream of your upstream marker. The faster the velocity the harder it is to time the travel over short distances. We recommend 20 feet as a minimum, but a travel time of around 20 seconds is best. Mark the beginning and end of the distance your floating object will travel. Choose a suitable channel section with minimum turbulence (ideally at least 3 channel widths long). V (Velocity) = Distance Traveled / Time to travel (feet traveled divided by seconds) We recommend doing these calculations in Feet and Seconds for convenience in converting to CFS (Cubic Feet Per/Second flow rate).Д¬FS = A x V (area multiplied by velocity)ДЄ (Area) = Width of Channel (feet) x Depth of Water (feet)

Optional waders (you will usually get wet if doing this correctly).

Stakes or rocks for anchoring tape measure to channel banks (can act as markers).

Three highly visible buoyant objects such as a sticks or logs, pine cone, or oranges (objects heavy enough not to be effected by the wind).

Yard or meter stick to measure depth (tape measures are more difficult to use).

Stop-watch (cell phones often have a timer).

Cfs meaning water