Considerations on direct stream flow measurements using video imagery: Outlook and research needs

The paper presents measurements acquired with Large-Scale Particle Image Velocimetry (LSPIV) during normal flows and floods in the Iowa River (U.S.A). For normal flows, comparison is made with measurements obtained with Acoustic Doppler Current Profilers (ADCP) in order to test LSPIV’s performance and to address concerns potentially affecting the accuracy of the measurements. The historic flood of the Iowa River during the summer of 2008 was captured for testing LSPIV capabilities during extreme flows. Lacking alternative measurements during the flood, the LSPIV measurements are compared to the rating curve extrapolated for high flows using a one-to-one discharge–stage relationship. The comparison reveals limitations of the single-values rating curve for providing discharge estimates during high flows. Finally, the paper summarizes lessons learned during these and previous LSPIV studies with the intent to chart the research needed to enhance this promising non-intrusive field measurement technique.

► The paper compares the Large-Scale Particle Image Velocimetry (LSPIV) with an alternative river discharge instrument: the Acoustic Doppler Current Profiler to highlight LSPIV advantages and limitations.
► The paper reports direct discharge measurements acquired with LSPIV during a historical flood to illustrate the interplay between river stage and discharge occurring on the rising and falling limbs of the hydrograph.
► The paper recommends further lines of research for improving the deficiencies of the emerging LSPIV technique and for revisiting the conventional rating curves estimation.