An Imaging Technique for Laboratory Water Depth Measurement of Rapidly Varying Flows

A recently proposed technique based on high resolution digital images for the acquisition of water depths in rapidly varying free surface flows is discussed. The addition of a coloring agent to the water allows to obtain a spatially distributed information of depths after the image conversion through a proper transformation function derived from a preliminary calibration. This technique was validated on the basis of the results of some laboratory dam-break tests by comparing water depth time series obtained from the post-processing of images with those returned by ultrasonic distance meters in six gauge locations. The influence of RAW and JPEG acquisition formats was investigated. The results show an accuracy comparable to that of ultrasonic transducers. The proposed imaging technique is thus preferable thanks to its capability of acquiring distributed water depth information for flows characterized by high spatial variability.