Application of aerial LSPIV to the 2002 flood of the Yodo River using a helicopter mounted high density video camera

Conventional Large-Scale Particle Image Velocimetry (LSPIV) implementation to river flow measurement is based on video recordings acquired with the camera set at a fixed location. During floods, it is of high interest to map reach of rivers that are at bankfull stage or flowing over the floodplain. In order to accommodate this interest a new approach is proposed in this paper, whereby images are taken from a helicopter that survey the region of interest. Visualization of the free surface during the high flood flows is obtained by taking advantage of the floating debris, ripples at the free surface, and water color gradients created by the high velocities. The new image acquisition procedure requires adjustments in the image processing protocols. The paper describes the adjustments made to the conventional software to accommodate the implementation of aerial LSPIV accompanied by considerations of its uncertainties. The unique capabilities of the aerial LSPIV in comparison with any other existing velocity and discharge measurement means is demonstrated by its implementation during the 2006 flood in Yodo River (Japan).

► Aerial large-scale particle image velocimetry (LSPIV) was developed that uses video images from a helicopter. ► A formula for appropriate speed of a helicopter with respect to surface flow and image size is proposed. ► The surface features are categorized into three types with specific surface images during flood. ► The estimated peak discharge of the Yodo River flood yields a relative error of six percent with gauging data.