Evaluating the use of SfM (Structure from Motion) as a tool for monitoring post restoration fluvial dynamics

Abstract

River restoration has become increasingly important as drivers such as the Water Framework Directive (WFD) aim to promote a culture of “healthy” and balanced river systems. There is a need to monitor these schemes to learn from past mistakes and provide adequate knowledge transfer between all stakeholders. Identifying and promoting new and novel techniques which can aid this knowledge transfer and monitoring of restoration schemes over a variety of spatial and temporal scales is significant for future applications. A platform to collect imagery, Unmanned Aerial Vehicles (UAVs) and a technique to process them Structure from Motion (SfM) is evaluated to assess how the workflows presented can be used in a restoration monitoring capacity along the Whit Beck, Cumbria. Three UAV surveys (October 2014, March 2015 and July 2015) were carried out and initial results suggest that higher image overlaps and increased number of targets result in better quality Digital Elevation Models (DEMs). DEMs were built using the optimum conditions discussed, and bathymetric correction was carried out using a refraction correction technique on wetted areas. A DEM of difference (DoD) technique was used to map patterns of erosion and deposition using two SfM DEMs from two differing surveys, while hydraulic modelling of the DEM allowed geomorphic units to be mapped. SfM offers a low cost, high point density approach with comparable spatial-temporal dynamics to Terrestrial Laser Scanning (TLS) datasets. However, a number of limitations, most notably vegetation penetration and shallow bathymetry have been noted. The approach does however have great potential if these drawbacks can be improved and can also be used as a tool for communicating geomorphology to a wider audience.

Date of Award	2017
Original language	English
Awarding Institution	Aberystwyth University
Sponsors	Knowledge Economy Skills Scholarships
Supervisor	Stephen Tooth (Supervisor)