Laboratory Evaluation of Flow Sensor Technology for Use in Storm Sewer Measurements

Accurate, accessible, and effective measurements of water depth and velocity are critical for developing hydrologic and hydraulic models that effectively characterize urban stormwater drainage systems. Well-informed decisions are contingent on the quality of hydrologic and hydraulic measurements, and while numerous technologies for flow quantification are available, information on their general applicability for stormwater measurements is lacking. This paper describes the laboratory measures taken prior to the field installation of several water quantity measurement sensors to ascertain the suitability of the devices for their intended use. Testing these devices in a controlled laboratory flume allows for observational and quantitative evaluation of a sensor's ability to perform in a storm sewer pipe. The testing and evaluation methods, and results of testing on several popular depth and velocity sensors are presented in order to provide recommendations for storm sewer authorities, researchers, and others that want to quantify storm sewer discharge, but do not have the facilities necessary to perform front-end testing of devices. Outcomes include evaluation of within-sensor variance, comparison of sensor performance between various stage and velocity technologies and manufacturers, and recommendations for sensor evaluation procedures, and general cautions before deployment in a stormwater system.