Reach scale analysis of riparian vegetation interactions with fluvial morphology using UAV based laser scanning and multispectral imaging

River corridors are greatly influenced by vegetation, whether it be through direct interactions with flow, influencing the stability of banks, or contributing to floodplain roughness. With vegetation present across many of the world’s river corridors in one form or another, it is a vital component of the active river corridor that receives relatively less attention than the flow and morphological components. This is partly because the routine monitoring of the very complex and temporally dynamic structure of vegetation is challenging.  Terrestrial Laser Scanning (TLS) and Airborne Laser Scanning (ALS) have been used to monitor fluvial vegetation across scales. However, whilst UAVs and Structure from Motion (SfM) techniques have recently bridged the gap between fine scale local surveys and coarse larger surveys for fluvial morphology, they are not well suited to characterising complex vegetation.

A UAV based laser scanning and imagery system has been developed which enables the collection of high resolution (> 300 points m2) point cloud data (first and last return) to analyse vegetation structure alongside simultaneous multispectral imagery data, including the red edge band. Such data can be collected on scales from metres to kilometres depending on the needs of the user, and is capable of picking out vegetation structure using metrics such as stand height, vertical distribution, canopy health, plant density etc. Moreover, the collection of this data through time will allow the evaluation of how these factors change across seasons, subsequently filling a void in data collection between spatially limited TLS and temporally limited ALS. Here we show some examples of how the data can be used to establish interactions between vegetation, flow and fluvial morphology from a series of flights over a 1 km reach of the River Teme, UK. These examples highlight how the data enables us to begin to establish a more detailed conceptual understanding of temporally evolving fluvial-vegetation interactions along river corridors.