Since the late 1990s, image sequence analysis velocimetry techniques (such as PIV – Particle Image Velocimetry) developed in the laboratory have been gradually applied to outdoor geophysical flows, particularly watercourses (Fujita et al. 1998; Hauet 2006). The movement of tracers (natural or added) visible on the surface of the flow is detected by autocorrelation of patterns from one image to the next, after orthorectification of the images; the surface velocity fields thus obtained can be filtered and averaged over a series of image pairs to establish the average velocity field; using one or more bathymetric transects and coefficients linking surface velocity and depth-average velocity, one or more discharge estimates can be calculated.
Among other image velocimetry techniques, LSPIV (Large Scale PIV) is a non-intrusive measurement technique (without contact with flow) providing instant and average two-dimensional velocity fields on a supposedly plane surface, as well as discharge estimates. It is particularly advantageous in the case of dangerous flows (e.g. fast floods), without absolute constraints of slow or fast velocity (by adapting the time interval between images), provided that the movement to be detected is visible in the video. In operational hydrometry, the technique is successfully applied for gauging campaigns (cf. Jodeau et al., 2008; Dramais et al., 2011), automated stations (flood gauging, cf. Le Coz et al., 2010; Hauet, 2016), and post-event, crowd-sourced video analysis (cf. Le Boursicaud et al., 2016 ; Le Coz et al., 2016).
The Fudaa-LSPIV open source software (Le Coz et al., 2014) has been co-developed and distributed by EDF and Irstea with DeltaCAD since 2010. User days have been organized every year in Lyon since 2017.
Link to the software and its documentation: https://forge.irstea.fr/projects/fudaa-lspiv/news
Reference to be cited on the software: Le Coz, J., Jodeau, M., Hauet, A., Marchand, B., Le Boursicaud, R. (2014) Image-based velocity and discharge measurements in field and laboratory river engineering studies using the free FUDAA-LSPIV software. River Flow 03/09/2014-05/09/2014, Lausanne, Switzerland. 7 p.
Tutorial videos: https://www.youtube.com/channel/UCZ8HFyQBfXz1O_pHbiiR7Vg/
References on Fudaa-LSPIV or using Fudaa-LSPIV
Benacchio, V., Piégay, H., Buffin-Bélanger, T., Vaudor, L. (2017) A new methodology for monitoring wood fluxes in rivers using a ground camera: Potential and limits, Geomorphology, 279, 44-58.
Camenen, B., Paquier, A., Bouarab, A., Le Coz, J., Dramais, G., De Linares, M. (2011) 2DH modelling of a reservoir flushing compared with LSPIV measurements. 34th IAHR World Congress, 26/06/2011-01/07/2011, Brisbane, Australia. 8 p.
Dramais, G., Le Coz, J., Camenen, B., Hauet, A. (2011) Advantages of a mobile LSPIV method for measuring flood discharges and improving stage-discharge curves, Journal of Hydro-Environment Research, 5, 301-312.
Hauet, A. (2006) Estimation de débit et mesure de vitesse en rivière par Large-Scale Particle Image Velocimetry [Discharge estimates and velocity measurements using Large-Scale Particle Image Velocimetry] (in French), PhD thesis, INP Grenoble, France.
Hauet, A. (2016) Monitoring river flood using fixed image-based stations: Experience feedback from 3 rivers in France, in: RiverFlow 2016, St. Louis, USA, July 11-14, 2016, pp. 541–547.
Jodeau, M., Hauet, A., Paquier, A., Le Coz, J., Dramais, G. (2008) Application and evaluation of LS-PIV technique for the monitoring of river surface velocities in high flow conditions. Flow Measurement and Instrumentation, 19 :117-127.
Jodeau, M., Hauet, A., Le Coz, J., Bercovitz, Y., Lebert, F. (2016) Laboratory and field LSPIV measurements of flow velocities using Fudaa-LSPIV, a free user-friendly software, HydroSenSoft, International Symposium and Exhibition on Hydro-Environment Sensors and Software, 1-3 March 2017, Madrid, Spain, 2 p.
Le Boursicaud, R., Pénard, L., Hauet, A., Le Coz, J. (2016) Gauging extreme floods on YouTube : Application of LSPIV to home movies for the post-event determination of stream discharges, Hydrological Processes, 30, 90-105.
Le Coz, J., Hauet, A., Pierrefeu, G., Dramais, G., Camenen, B. (2010) Performance of image-based velocimetry (LSPIV) applied to flash-flood discharge measurements in Mediterranean rivers, Journal of Hydrology, 394 (1-2), 42-52.
Le Coz, J., Jodeau, M., Hauet, A., Marchand, B., Le Boursicaud, R. (2014) Image-based velocity and discharge measurements in field and laboratory river engineering studies using the free FUDAA-LSPIV software. River Flow 03/09/2014-05/09/2014, Lausanne, Switzerland. 7 p.
Le Coz, J., Patalano, A., Collins, D., Guillén, N. F., García, C. M., Smart, G. M., Bind, J., Chiaverini, A., Le Boursicaud, R., Dramais, G., Braud, I. (2016) Crowdsourced data for flood hydrology: feedback from recent citizen science projects in Argentina, France and New Zealand, Journal of Hydrology, 541, 766-777
Legoût, C., Darboux, F., Nedelec, Y., Hauet, A., Esteves, M., Renaux, B., Denis, H., Cordier, S. (2012) High spatial resolution mapping of surface velocities and depths for shallow overland flow, Earth Surface Processes and Landforms, 37(9), 984-993.
Piton, G., Recking, A., Le Coz, J., Bellot, H., Hauet, A., Jodeau, M. (2018) 2D reconstruction of low-submergence, mobile-bed flows: an inverse method combining LS-PIV and Structure-from-Motion photogrammetry, Water Resources Research, 54(6), 4164-4179.
Recking, A., Piton, G., Montabonnet, L., Posi, S., Evette, A. (2019) Design of fascines for riverbank protection in alpine rivers: Insight from flume experiments, Ecological Engineering, 138, 323-333.
Theule, J.I., Crema, S., Marchi, L., Cavalli, M., Comiti, F. (2018) Exploiting LSPIV to assess debris-flow velocities in the field, Natural Hazards and Earth System Sciences, 18(1), 1-13
Zhu, X., Lipeme Kouyi, G. (2019) An analysis of LSPIV-based surface velocity measurement techniques for stormwater detention basin management, Water Resources Research, 55(2), 888-903.