New views of the morphodynamics of large braided rivers from high-resolution topographic surveys and time-lapse video

Four new technologies were combined to investigate morphological change along a 4 km reach of the 1-km-wide, braided, gravel-bed Waimakariri River on New Zealand's South Island. River-bed topography was surveyed four times over 15 months, capturing the change caused by near-bankfull flood events. Dry areas of river bed were surveyed either with digital photogrammetry or airborne laser scanning. A combination of remote-sensing and ground-based bathymetry was used to survey the beds of wetted braids. Two video cameras, mounted 35 m above the river bed, provide hourly daytime imagery of the central area of the study reach and an invaluable record of the coherence of morphologic features. This data set provides a view of form and process in a large braided river that has hitherto only been possible in laboratory channels, and identifies features such as low relief drainage basins that appear to be unique to field-scale braided channels.