Submitted to: Hydrological Science and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 1, 2000
Publication Date: N/A
Interpretive Summary: When trying to determine the discharge from a stream one of the needed components is velocity. Ways of determining velocity include building a control structure in which known velocities exists for known depths or by standing in the stream with a velocity meter. Access to build a structure and the duration of the flow event can cause difficulties in measuring velocity with these methods at remote locations. A continuous time velocity profile measuring device was developed, using technology from a hand held velocity meter. The velocity measurements then permitted the calculation of a depth versus discharge relationship.
Technical Abstract: The primary objectives of this paper are to: 1) describe an automated technique developed to collect velocity and flow depth data for small streams in remote locations and 2) describe a method for developing a rating curve from measured velocity and flow depth data. The velocity tree system was designed and developed for use with an automated bubbler/sampler to provide water quality samples and to relate measured velocities with flow depth. This system provides a safe, reliable, and time-efficient alternative to the common practice of traveling to a site and collecting velocity data with a hand-held velocity meter while standing in the stream. It also allows velocities to be measured for remote locations difficult to reach during short duration runoff events. Impeller clogging and blocking are disadvantages that may limit the amount of velocity data collected. To develop a rating curve, average velocities recorded in each flow depth interval were plotted versus impeller depth. From these plots, an exponential best-fit equation (velocity profile) was developed and solved for mean velocity. Discharge was calculated by multiplying mean velocity for each depth interval by flow area and used to produce the depth versus discharge relationship.