Sediment pulses are triggered through a variety of mechanisms, from landslides to land use change. How do these pulses move through the fluvial system, and how do they evolve? In a system with perfect sediment connectivity, the erosional response to a perturbation and the resulting signal at the river mouth would match, however, this rarely occurs. Many studies have addressed reach-scale dynamics of sediment pulses and how they translate or disperse downstream. At the watershed scale, network structure and storage become more important in modulating the sediment signal. Here, we review the current literature on sediment pulse behavior, and then address the role of network structure on maintaining, dispersing, or transforming sediment pulses in a fluvial system. We use a reduced-complexity network routing model that simulates the movement of bed material through a river basin. This model is run in the Greater Blue Earth River (GBER) basin in Minnesota, USA, first with spatially uniform inputs and then with inputs constrained by a detailed sediment budget. Once the system reaches equilibrium, a sediment pulse is introduced, first at a single location and then throughout the system, and tracked as it evolves downstream. Results indicate that pulses able to translate downstream disperse in place upon arriving at over-capacity reaches as sediment goes into storage. In the GBER basin, these zones occur just upstream of a knickpoint that is propagating upstream through all mainstem channels. As the pulses get caught in these sediment “bottlenecks,” there is a decoupling of the original pulse of sediment and the resulting bed material wave. These results show that the network structure, both in terms of network geometry and the spatial pattern of transport capacity, can play a dominant role in sediment connectivity and should be considered when predicting sediment pulse behavior at the watershed scale.
Bibliographical noteFunding Information:
This research was funded by NSF grant EAR-1209402 under the Water Sustainability and Climate Program with additional funding for the sediment budget from the Minnesota Department of Agriculture through Minnesota's Clean Water Legacy Fund. JAC acknowledges support provided by an Interdisciplinary Doctoral Fellowship through the University of Minnesota's Graduate School and Institute on the Environment and by an Edward Silberman Fellowship through St. Anthony Falls Laboratory . The sediment budget was originally compiled by Martin Bevis, with bluff erosion rates measured by Stephanie Day and Girish Uprety. We appreciate the comments from Dr. Stephen Rice and one anonymous reviewer that helped improve this manuscript.
© 2015 Elsevier B.V.
- Network routing
- Sediment connectivity
- Sediment pulse
- Sediment wave