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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.

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Glaciers are a major erosive force that increase sediment load to the downstream fluvial system. The Castle Creek Glacier, British Columbia, Canada, has retreated ~1.0 km in the past 70 years.Suspended sediment concentration (SSC) and streamflow (Q) were monitored independently at five sites within its proglacial zone over a 60 day period from July to September, 2011, representing part of the ablation season. Meteorological data were collected from two automatic weather stations proximal to the glacier. The time-series were divided into hydrologic days and the shape and magnitude of the SSC response to hydro-meteorological conditions ('cold and wet', 'hot and dry', 'warm and damp', and 'storm') were categorized using principal component analysis (PCA) and cluster analysis (CA). Suspended sediment load (SSL) was computed and summarized for the categories. The distribution of monitoring sites and results of the multivariate statistical analyses describe the temporal and spatial variability of suspended sediment flux and the relative importance of glacial and paraglacial sediment sources in the proglacial zone. During the 2011 study period, ~ 60% of the total SSL was derived from the glacial stream and sediment deposits proximal to the terminus of the glacier; during 'storm' events, that contribution dropped to ~40% as the contribution from diffuse and point sources of sediment throughout the proglacial zone and within the meltwater channels increased. While 'storm' events accounted for just 3% of the study period, SSL was ~600% higher than the average over the monitoring period, and ~20% of the total SSL was generated in that time. Determining how hydro-meteorological conditions and sediment sources control sediment fluxes will assist attempts to predict how proglacial zones respond to future climate changes.

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