, 2011). The preponderance of deposition in small watersheds suggests that LS deposits are most likely to be found in tributary locations if storage sites
are available, MK-2206 mouse but that this sediment will be reworked and redistributed downstream through time. A late 20th century trend in some North American catchments has been for SDRs that were much less than one, owing to high soil erosion rates, to increase as soil conservation measures were employed. As upland sediment production decreases, sediment yields remain constant by recruitment of LS from channel banks and floodplains (Robinson, 1977). The dynamics implied by sediment delivery theory have great import to interpretations of LS. Sediment yields in the modern world are not static as was once assumed, but have a dynamic behavior that is largely driven by the legacy of past sedimentation events (Walling, 1996). Temporal variability occurs in the form of regional differences between large basins
and by variability in sediment retention times within a basin. Regional differences reflect the cultural histories of landscapes; i.e., times of settlement and intensities of land use, as well as differences in the physical characteristics. Variations in sediment Tyrosine Kinase Inhibitor Library retention time within a catchment is one of the greatest sources of uncertainty Cediranib (AZD2171) in computing sediment yields and sediment budgets for watersheds (Wolman, 1977 and Gellis et al., 2009). Temporal connectivity is an important element of LS and sediment delivery theory, because past deposits are reworked and transported downslope for long periods of time after initial
deposition. This is, in fact, why ‘legacy’ is an appropriate way to describe these sediments; they are an inheritance from times past that should be reckoned with. Numerous studies of anthropogeomorphic impacts since the Neolithic have documented sedimentation events in a variety of geomorphic environments. Legacy sediment (LS) is now commonly used in geomorphic, ecological, water quality, and toxicological studies to describe post-settlement alluvium on river floodplains. Most applications of LS imply or explicitly attribute the sediment to human landscape changes, but explicit definitions have been lacking that are sufficiently broad to apply LS to the variety of applications now common. The concept of LS should apply to anthropogenic sediment that was produced episodically over a period of decades or centuries, regardless of position on the landscape, geomorphic process of deposition, or sedimentary characteristics; i.e., it may occur as hillslope colluvium, floodplain alluvium, or lacustrine and estuarine slackwater deposits.