Topo-bathymetric airborne LiDAR for fluvial-geomorphology analysis

International audienceTopographic airborne lidar using a near-infrared laser cannot penetrate water. A new generation of topo-bathymetric sensors adds a green laser to measure shallow bathymetry. We synthesize previous work and present new results using these sensors in the context of fluvial geomorphology. These sensors allow synoptic continuous topography and bathymetry with a vertical accuracy better than 10 cm and a capacity to resolve details of 20–30 cm. The maximum measurable depth can vary from 1 to 6 m depending on water turbidity, bottom reflectance, and the sensor used. Based on a 55 km survey of the Ain River (France), we illustrate the level of detail recorded in raw data, the full-waveform record, and the challenges in detecting individual bathymetric points that require a refraction correction among billions of points. We show various applications, including synoptic measurement of erosion/sedimentation, back calculation of water optical properties, and large-scale, high-resolution mapping of inundation patterns