Spatial and Temporal Variations in Landscape Evolution: Historic and Longer-Term Sediment Flux through Global Catchments

Sediment generation and transport through terrestrial catchments influence soil distribution, geochemical cycling of particulate and dissolved loads, and the character of the stratigraphic record of Earth history. To assess the spatial and temporal variation in landscape evolution, we compare global compilations of stream gauge-derived (n = 1241) and cosmogenic radionuclide (CRN)-derived (predominantly Be-10; n = 1252) denudation of catchments (mm/yr) and sediment load of rivers (Mt/yr). Stream gauges measure suspended sediment loads of rivers during several to tens of years, whereas CRNs provide catchment-integrated denudation rates at 10(2)-10(5)-yr time scales. Stream gauge-derived and CRN-derived sediment loads in close proximity to one another (<500 km) exhibit broad similarity (n = 453 stream gauge samples; n = 967 CRN samples). Nearly two-thirds of CRN-derived sediment loads exceed historic loads measured at the same locations (n = 103). Excessive longer-term sediment loads likely are a result of longer-term recurrence of large-magnitude sediment-transport events. Nearly 80% of sediment loads measured at approximately the same locations exhibit stream gauge loads that are within an order of magnitude of CRN loads, likely as a result of the buffering capacity of large flood plains. Catchments in which space for deposition exceeds sediment supply have greater buffering capacity. Superior locations in which to evaluate anthropogenic influences on landscape evolution might be buffered catchments, in which temporary storage of sediment in flood plains can provide stream gauge-based sediment loads and denudation rates that are applicable over longer periods than the durations of gauge measurements. The buffering capacity of catchments also has implications for interpreting the stratigraphic record; delayed sediments transfer might complicate the stratigrphic record of external forcings and catchment modification.