Loops in Coastal Channel Networks: a theoretical, experimental, and field-based investigation of their morphodynamic stability

River channels constructed by the movement of water and sediment act as the fundamental plumbing for civilizations. The channel networks that cover river deltas can take many shapes or topologies. Sometimes, they branch and reconnect to form loops within the network. Some networks have many hundreds of such loops. Existing theory suggests that loops should be unstable: part of the loop should fill with sediment. However, loops have persisted on some river deltas for centuries. This project will explore what keeps such loops stable, and systematically study this fundamental component of many coastal landscapes. The project will analyze loop stability with three complimentary approaches. First, a theoretical derivation will be developed to predict when loops can maintain stability: what flows allow all the channels in the loop to remain open and not choked with sediment? Second, a channel network with a loop will be constructed in the laboratory such that the equilibrium conditions of water and sediment transport can be measured for any imposed flow pattern. Third, model outputs from the heavily monitored Sacramento-San Joaquin Delta in California will be used to test the theory for a real delta that displays many loops. By considering these three disparate approaches, the researchers anticipate an improved understanding of loops in channel networks that is general enough to be applied widely. This project was jointly funded by Geomorphology and Land-Use Dynamics (GLD), Division of Environmental Biology Ecosystem Science (DEB) and EAR EPSCoR funding. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.