The Accuracy and Reliability of Traditional Surface Flow Type Mapping: Is It Time for A New Method of Characterising Physical River Habitat?

Surface 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, and provide new opportunities for examining the heterogeneity of physical habitat over a range of spatial and temporal scales. Whilst continued refinement of the sUAS-SfM approach is required, we propose that this method offers an opportunity to move away from broad, mesoscale classifications of physical habitat (spatial scales 10-100m), and towards continuous, quantitative measurements of the continuum of hydraulic and geomorphic conditions which actually exists at the microscale.

The Glow of Unwork? Issues of Portrayal in Networked Learning Research

In this paper, we suggest that portrayal of research is often undervalued and seen as ‘unwork’ (Galloway, 2012). Portrayal is often seen as an issue that is relatively straight forward by qualitative researchers, and invariably refers to putting the findings of the study together with excerpts from participants and usually, but not always, some interpretation. It tends to be seen as the means by which the researcher has chosen to position people and their perspectives, and it is imbued with a sense of not only positioning but also a contextual painting of a person in a particular way. Yet there are an array of issues and challenges about what portrayal can or might mean in digital spaces. In this paper we argue that researching education in a digital age provides greater or different opportunities to represent and portray data differently and suggest that these ways are underutilised. For example, for many researchers legitimacy comes through the use of participants’ voices in the form of quotations. However, we argue that this stance towards plausibility and legitimacy is problematic and needs to be reconsidered in terms of understanding differences in types of portrayal, recognizing how researchers position themselves in relation to portrayal, and understanding decision-making in relation to portrayal. We suggest that there need to be new perspectives about portrayal and concept, and ideas are provided that offer a different view. Three key recommendations are made: Portrayal should be reconceptualised as four overlapping concepts: mustering, folding, cartography, and portrayal. Adopting such an approach will enable audiences, researchers and other stakeholders to critique the assumptions that researchers on tour bring to portrayal and encourage reflexivity. Researchers on tour should highlight the temporal, mutable and shifting nature of portrayed research findings, emphasising the need for continued and varied research to inform understanding. There is a significant need for greater insight into the influence of portrayal, as well as the difference between representation and portrayal. Future studies should prioritise this, and ensure that portrayal is considered and critiqued from the outset.