Quantifying the topography of rivers and their associated bedforms has been a fundamental concern of fluvial geomorphology for decades. Such data, acquired at high temporal and spatial resolutions, are increasingly in demand for process‐oriented investigations of flow hydraulics, sediment dynamics and in‐stream habitat. In these riverine environments, the most challenging region for topographic measurement is the wetted, submerged channel. Generally, dry bed topography and submerged bathymetry are measured using different methods and technology. This adds to the costs, logistical challenges and data processing requirements of comprehensive river surveys. However, some technologies are capable of measuring the submerged topography. Through‐water photogrammetry and bathymetric LiDAR are capable of reasonably accurate measurements of channel beds in clear water. While the cost of bathymetric LiDAR remains high and its resolution relatively coarse, the recent developments in photogrammetry using Structure from Motion (SfM) algorithms promise a fundamental shift in the accessibility of topographic data for a wide range of settings. Here we present results demonstrating the potential of so called SfM‐photogrammetry for quantifying both exposed and submerged fluvial topography at the mesohabitat scale. We show that imagery acquired from a rotary‐winged Unmanned Aerial System (UAS) can be processed in order to produce digital elevation models (DEMs) with hyperspatial resolutions (c. 0.02 m) for two different river systems over channel lengths of 50–100 m. Errors in submerged areas range from 0.016 m to 0.089 m, which can be reduced to between 0.008 m and 0.053 m with the application of a simple refraction correction. This work therefore demonstrates the potential of UAS platforms and SfM‐photogrammetry as a single technique for surveying fluvial topography at the mesoscale (defined as lengths of channel from c.10 m to a few hundred metres). Copyright © 2014 John Wiley & Sons, Ltd.

(2016) 'The accuracy and reliability of traditional surface ow type mapping : is it time for a new method of characterizing physical river habitat?', River research and applications., 32 (9). pp. 1902-1914. Further information on publisher's website:https://doi.org/10.1002/rra.3047 Publisher's copyright statement: This is the accepted version of the following article: Woodget, A. S., Visser, F., Maddock, I. P., and Carbonneau, P. E. (2016) The Accuracy and Reliability of Traditional Surface Flow Type Mapping: Is it Time for a New Method of Characterizing Physical River Habitat?. River Research and Applications, 32(9): 1902-1914, which has been published in nal form at https://doi.org/10.1002/rra.3047. This article may be used for non-commercial purposes in accordance With Wiley Terms and Conditions for self-archiving.Additional information: Use policyThe full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. AbstractSurface flow types (SFT) are advocated as ecologically relevant hydraulic units, often mapped visually from the bankside to characterise rapidly the physical habitat of rivers. SFT mapping is simple, non-invasive and cost-efficient. However, it is also qualitative, subjective and plagued by difficulties in recording accurately the spatial extent of SFT units. Quantitative validation of the underlying physical habitat parameters is often lacking, and does not consistently differentiate between SFTs. Here, we investigate explicitly the accuracy, reliability and statistical separability of traditionally mapped SFTs as indicators of physical habitat, using independent, hydraulic and topographic data collected during three surveys of a c. 50m reach of the River Arrow, Warwickshire, England. We also explore the potential of a novel remote sensing approach, comprising a small unmanned aerial system (sUAS) and Structure-from-Motion photogrammetry (SfM), as an alternative method of physical habitat characterisation. Our key findings indicate that SFT mapping accuracy is highly variable, with overall mapping accuracy not exceeding 74%. Results from analysis of similarity (ANOSIM) tests found that strong differences did not exist between all SFT pairs. This leads us to question the suitability of SFTs for characterising physical habitat for river science and management applications. In contrast, the sUAS-SfM approach provided high resolution, spatially continuous, spatially explicit, quantitative measurements of water depth and point cloud roughness at the microscale (spatial scales ≤1m). Such data are acquired rapidly, inexpensively...

No abstract

15Remote sensing has rarely been used as a tool to map and monitor submerged aquatic

A framework for evaluating the spatial configuration and temporal dynamics of hydraulic patches was tested in a UK lowland river. Detailed hydraulic assessment was carried out at four discharges between 0.303 m3 s−1 and 1.410 m3 s−1 in a 56 m reach. Five hydraulic patches, as combinations of depth and mean column velocity, and the transitional zones between them were delineated using fuzzy cluster analysis. The composition and configuration of the hydraulic patch mosaic was quantified using spatial metrics. Results showed that the proportion, size, shape and relative location of hydraulic patches all varied with discharge, however intermediate flows appeared to support the most diverse hydraulic patch composition and configuration. This suggests the spatial influence of mesoscale bedforms on hydraulic patches is mediated by temporal variations in discharge. Transitional areas between hydraulic patches occupied a significant proportion of the reach at all flows (33–38%) and may function as in‐stream ecotones. The framework addresses the need for a quantitative, spatially explicit approach to hydraulic assessment which could be used to assess the implications of flow regulation and hydromorphological alteration on hydraulic diversity. Copyright © 2010 John Wiley & Sons, Ltd.