Connectivity’ has been a major theme in UK fluvial research in recent years, particularly in empirical contexts of coarse sediment transfer Ribociclib ic50 in upland environments involving gully, fan and adjacent floodplain (Harvey, 1997 and Hooke, 2003), and in the transfer of sediment within valleys in the form of sediment slugs or waves (Macklin and Lewin, 1989 and Nicholas et al., 1995). These and studies elsewhere have commonly used morphological estimates and budgeting

of sediment flux, both from historical survey comparisons (decades to centuries) and from reconnaissance assessments of apparently active erosion or sedimentation sites. On the longer timescale necessary for assessing human impact, whole-catchment modelling involving Holocene sediment routing has also demonstrated how complex and catchment specific these internal transfers may be in response to climatic and land cover changes (Coulthard et al., 2002 and Coulthard et al., 2005). Major elements of UK catchment relief

involve variable lithologies, selleck over-steepened to low-gradient slopes, rock steps, alluvial basins, and valley fills inherited from prior Pleistocene glacial and periglacial systems (Macklin and Lewin, 1986). Some of these locally provide what may be called ‘memory-rich’ process environments. Progressive and ongoing Holocene evacuation of coarse Pleistocene valley fills is of major significance in a UK context (Passmore and Macklin, 2001), and this differs from some of the erodible loess terrains in which many other AA studies have been conducted in Europe and North America (e.g. Trimble, 1983, Trimble, 1999, Lang et al., 2003, Knox, 2006, Houben, 2008, Hoffman et al., 2008 and Houben et al., 2012). Human activities have greatly modified hydrological systems, and in different ways: in terms of discharge response to precipitation and extreme events,

but also in the supply of sediment. For finer sediments (where sediment loadings are generally supply-limited rather than competence-limited), dominant yield events (near bankfull) and sediment-depositing events (overbank) may not be the same. Holocene flood episodes (Macklin et al., 2010) may also be characterized by river incision (Macklin et al., 2013) as well as by the development of thick depositional sequences (Jones et al., 2012), of depending on river environment. Fine sediment may be derived from surface soil removal, through enhanced gullying and headwater channel incision, from reactivation of riparian storages, or through the direct human injection or extraction of material involving toxic waste or gravel mining. For a millennium and more, channel-way engineering has also transformed systems to provide domestic and industrial water supply, water power for milling, improved passage both along and across rivers, fisheries improvement, and for flood protection (Lewin, 2010 and Lewin, 2013).