Non-contact laser doppler velocity meter in a Hampton Roads stormwater pipe

Detailed Description
Non-contact laser doppler velocity meters use a laser to measure water velocity throughout a channel's cross-section, while another part of the device is measuring the depth of water. Together the two datasets are used to compute streamflow. In this photo, USGS researcher Chelsea Vande Pol indicates where a laser meter is taking continuous measurements of water velocity and depth.
Sources/Usage
Public Domain.