River bank erosion occurs primarily through a combination of three mechanisms: mass failure, fluvial entrainment, and subaerial weakening and weathering. Subaerial processes are often viewed as 'preparatory' processes, weakening the bank face prior to fluvial erosion. Within a river basin downstream process 'domains' occur, with subaerial processes dominating the upper reaches, fluvial erosion the middle, and mass failure the lower reaches of a river. The aim of this paper is to demonstrate that (a) subaerial processes may be underestimated as an erosive agent, and (b) process dominance has a temporal, as well as spatial, aspect.Bank erosion on the River Arrow, Warwickshire, UK, was monitored for 16 months (December 1996 to March 1998) using erosion pins. Variations in the rate and aerial extent of erosion are considered with reference to meteorological data. Throughout the first 15 months all erosion recorded was subaerial, resulting in up to 181 mm a À1 of bank retreat, compared with 13 to 27 mm a À1 reported by previous researchers. While the role of subaerial processes as 'preparatory' is not contended, it is suggested that such processes can also be erosive.The three bank erosion mechanisms operate at different levels of magnitude and frequency, and the River Arrow data demonstrate this. Thus the concept of process dominance has a temporal, as well as spatial aspect, particularly over the short time-periods often used for studying processes in the field. Perception of the relative efficacy of each erosive mechanism will therefore be influenced by the temporal scale at which the bank is considered. With the advent of global climate change, both these magnitude-frequency characteristics and the consequent interaction of bank erosion mechanisms may alter. It is therefore likely that recognition of this temporal aspect of process dominance will become increasingly important to studies of bank erosion processes.
Recent studies of river bank erosion in three catchments in the UK have been characterized by the persistent occurrence of negative erosion-pin results. The cause of these negative recordings is considered with reference to field data from the Afon Trannon, Nant Tanllwyth and River Arrow, and to a laboratory study of freeze-thaw and desiccation processes. It seems that there is potential for, and in some cases evidence of, a number of different circumstances that generate negative results, but none of these alone is sufficient to explain all incidents. Factors considered include: deposition of sediment during high flows; soil fall from the upper parts of the bank on to lower erosion pins; loosening of the soil surface and expansion/contraction of the soil mass with fluctuations in temperature and moisture content; movement of the erosion-pin within the bank and human interference. Each has its own implications for the use of erosion pins.Further issues arise when including negative data in subsequent data analysis, and it is demonstrated that attempts to correlate erosion rates with hydro-meteorological data in order to ascertain causes of erosion will be influenced by the way in which negative data are handled. It is thus suggested that any study of river bank erosion using erosion pins should state whether or not negative data were obtained, and if so, how they were included in data analysis. Failure to include this information could lead to comparison of mean erosion rates that reflect bank processes very differently.The studies presented here offer a clear example of the value of 'anomalous' field data: results which do not appear to fit expected patterns can reveal as much about the processes in operation as those that do.
The intention of this article is to identify the ways in which ideas about space and time are manifest in river bank erosion research, thus linking abstract theoretical discussion with the 'practice' of geomorphological research. Bank erosion research to date has involved a range of space-and time-scales, different perspectives resulting from these views. Scale linkage via mathematical translation has been attempted in some cases, but studies are often contextualized through loosely hierarchical ideas. The application of hierarchy theory and notions of space-time are considered, concluding with the identification of questions that might usefully be considered in future research
This paper presents a broadly realist, pragmatist view of geography, drawing on the work of Wittgenstein to consider the role of language in the divide between human and physical geography. The possibility that we may have ideas that are structured similarly but expressed differently is illustrated through the application of Peircean semiotics to a hierarchy of geomorphological processes in a river system. The resulting ‘scalar semiotic fluvial hierarchy’ allows some of the criticisms of hierarchy to be addressed, and offers geomorphologists a framework for understanding multiple cross‐scale process interactions. Finally, the implications of a Wittgensteinian perspective for geography are considered.
The contact with nature provided by urban green and blue space is said to be beneficial for mental health, physical health, social contact and cohesion, and for learning and development among children. Yet the literature identifying these benefits fails to recognise that 'nature', as a category in binary relation with 'culture' (or 'humans'), is a cultural construct. Acknowledging this inevitably raises questions about exactly what 'contact with nature' in such spaces might consist in. Taking inspiration from more-than-representational and more-than-human geographies, this article uses Merleau-Ponty's phenomenology to interrogate encounters with 'nature' through small boat sailing. I argue that being on a boat entails different embodied spatialities of being from terrestrial urban life, and that this heightens a sense of nature as Other. The nature/culture binary, while a cultural idea, is materially (re)produced through the ordering of space, particularly in dense urban areas. This implies that the significance of urban green/blue space may be not only the presence of non-humans (the green/blue), but also the nature of the space in which we encounter nature. There is, then, potential for cultural geography to contribute to a much more nuanced interrogation of how people experience urban green/blue space, foregrounding the cultural conditions that shape such experience.
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