Manival Torrent, a small mountain stream located in the Northern French Prealps, experiences debris flows annually. The torrents catchment (3.6 km2, 1,200 m relief) is composed of marl and limestone beds with increasing limestone towards the ridge. A field monitoring program started in 2009 to study the geomorphic responses to flow events. The aim of this study is to implement an event-based sediment budget approach for monitoring coarse sediment transport and characterizing the spatial variability of the sediment response in the main channel. The monitoring of 38 cross-sections (within a 1.8 km length) provides total volumes of erosion and deposition throughout the main channel. At the downstream end of the surveyed reach, a sediment trap (capacity: 25,000 m3) is used for measuring sediment output. Terrestrial LiDAR is used for monitoring erosion and deposition wherever accessible in the catchment area which includes the sediment trap, reaches of the torrent, talus slopes, gullies, and cliffs. Precipitation is monitored by a rain gage in the upper catchment. An airborne LiDAR survey was done in spring 2009 providing a high-resolution DTM of the catchment. This intense field monitoring allows us to reconstruct morphological changes induced by a debris flow event that occurred on August 24, 2009. A sediment budget analysis was performed to determine the main sediment sources of the torrent and to evaluate the respective contribution of channels and hillslopes to the sediment yield.