Distributions of source grain size (bottom axis) across 1,422 sediment input points in a tributary network (82,400 km2) of the Mekong River. Source grain size at each input point is randomly assigned within a range of sand sizes (0.064 - 2 mm) and sediment is routed downstream. The gray distributions show the ensemble results of 7,500 simulations, while the colored distributions represent admissible solutions for the range of sand size and flux observed at the basin outlet (left color ramp). The right axis is the cumulative proportion of source grain size values. Credit: Schmitt et al., 2017, Figure 7b
Source: Journal of Geophysical Research: Earth Surface

Sediment that is transported through a river network represents a complex integration of multiple sources and sizes of sediment input. Determining source areas and their downstream integration is frequently hampered by insufficient data, particularly for large river basins, but has relevance for managing natural and anthropogenic disturbances of watersheds (for example, the effects of dams and diversions). Schmitt et al. [2017] use a stochastic sediment routing model that randomly assigns input grain size to a network of sediment sources, which when run repeatedly produces a distribution of potential solutions for the size and flux of sediment carried by the river. Point observations of grain size and sediment flux at the basin outlet are then used to constrain admissible solutions within the range of uncertainty of the observations, allowing inversion of the model to determine associated source grain sizes and sediment fluxes through the network. The approach also identifies bottlenecks in the river network that regulate the flux of sediment through the system. The stochastic framework allows powerful leveraging of limited field observations that can inform management plans and structure subsequent validation efforts to better understand physical controls on network sediment flux and routing.

Citation: Schmitt, R. J. P., Bizzi, S., Castelletti, A. F., & Kondolf, G. M. [2017]. Stochastic modeling of sediment connectivity for reconstructing sand fluxes and origins in the unmonitored Se Kong, Se San, and Sre Pok tributaries of the Mekong River. Journal of Geophysical Research: Earth Surface, 122. https://doi.org/10.1002/2016JF004105

—John Buffington, Editor, JGR: Earth Surface

Text © 2018. The authors. CC BY-NC-ND 3.0
Except where otherwise noted, images are subject to copyright. Any reuse without express permission from the copyright owner is prohibited.