Maintenance of large deltas through channelization: Nature vs. humans in the Danube delta

Liviu Giosan, Stefan Constantinescu, Florin Filip, Bing Deng

Over the last half century, while the total sediment load of the Danube dramatically decreased due to dam construction on tributaries and its main stem, a grand experiment was inadvertently run in the Danube delta: the construction of a dense network of canals, which almost tripled the water discharge toward the interior of the delta plain. We use core-based and chart-based sedimentation rates and patterns to explore the delta transition from the natural to an anthropogenic regime, to understand the effects of far-field damming and near-field channelization, and to construct a conceptual model for delta
development as a function sediment partition between the delta plain and the delta coastal fringe.

We show that sediment fluxes increased to the delta plain due to channelization counteracting sea level rise. In turn, the delta coastal fringe was most impacted by the Danube’s sediment load collapse. Furthermore, we suggest that morphodynamic feedbacks at the river mouth are crucial in trapping sediment near the coast and constructing wave-dominated deltas or lobes. Finally, we suggest that increased channelization that mimics and enhances natural processes may provide a simple solution for keeping other delta plains above sea level and that abandonment of wave-dominated lobes may be the most long term efficient solution for protecting the internal fluvial regions of deltas and provide new coastal growth downcoast.

Read the document here.