Study region: Houay Xon catchment in northern Laos.Study focus: Because agricultural headwater catchments of SE Asia are prone to erosion anddeliver a significant proportion of the total suspended sediment supply to major rivers andfloodplains, the potential sources of sediments and their dynamics were studied for twosuccessive storm flow events in June 2013. Characterization of suspended sediment loadswas carried out along a continuum of 7 monitoring stations, combining analyses of falloutradionuclides, particle borne organic matter and stream water properties.New hydrological insights: Radionuclide activities showed that remobilization of soil par-ticles deposited during the previous rainy season or supplied by riverbank erosion isthe dominant process, although pulses of surface-soil derived sediments also propagatedownstream. This interpretation is supported by suspended organic matter data that alsofingerprints the mixing of surface soil vs. subsurface particles. The study moreover high-lights the advantages and the drawbacks of combining fallout radionuclides, particle borneorganic matter composition and stream water characteristics to discriminate and quantifysediment sources and dynamics in rural areas undergoing urban sprawl.
