MEASUREMENT OF DEBRIS FLOW SURFACE VELOCITY BASED ON IMAGE PROCESSING TECHNIQUES

M. Arattano¹, P. Grattoni² and L. Marchi³

1CNR-IRPI, Strada delle Cacce 73, 10135 Torino, Italy
2CNR CSTV, Strada delle Cacce 91, 10135 Torino, Italy
3CNR IRPI, C.so Stati Uniti 4, 35127 Padova, Italy




Because of the great destructive power possessed by debris flows, that is often cause of severe damages to the properties on the fan of mountain torrents, measurements of their most important characteristics, such as flow height, impact force, velocity or volume are particularly important and might greatly help in the development of countermeasures and warning systems. Unfortunately in many cases devices, methods and procedures already developed and available for measuring analogous characteristics for clear water cannot be applied to debris flows. This is particularly true for the measurement of flow velocity, because of high flow density and the presence of boulders and smaller fragments within the moving mass that impedes the use of devices such as current meters, chemical tracers, weirs, flumes etc.. A new method based on the automated shooting of videos of debris flows and the subsequent use of image processing techniques to measure superficial velocities of debris flows is proposed. This method is based on the direct computation of the mapping between 2D image points and points in the 3D space without resort to a geometric calibration of the camera and of the scene. The method is applied to measure the surface velocities of a couple of debris flows that were video recorded in 1996 in north-eastern Italy.