Author(s): Diego Panici; Georgie Bennett

Linked Author(s): Diego Panici

Keywords: Flood; Landslide; Dam formation

Abstract: Landslides and debris flows represent natural phenomenon with high geomorphic impact. Intense rainfall events are key triggers of landslides and, as a result, landslides end up interacting with river channels during floods. Large masses of sediment can overwhelm the sediment transport capacity of a river channel and result in the formation of a dam. Eventually, the blockage is removed, leaving the process of dam build-up and bursting undocumented. When field evidence of this phenomenon is limited, modelling exercises may provide a viable way to test the hypothesised landslide-flood interactions. In this study, we show a preliminary analysis by using a computational model to replicate the formation of a channel blockage downstream of a series of landslides during an event that occurred in the North St Vrain Creek in Colorado, USA, during the Great Colorado Flood in September 2013 (estimated to be a 1 in 1000 year event). We employed the free source code r.avaflow, which is a three-phase model. This code can simulate complex chain phenomena, rapid routing mass flows, and entrainment-deposition processes. The model was able to represent the erosion from the landslides and on the river channel, but also revealed the formation of a dam downstream of the landslides across all simulations. Although the topographic change and volume of mobilised sediments were affected by the variation of the model parameters, the channel blockage was always observed. This modelling will provide the basis for further modelling of landslide-channel interactions and will explain those phenomena that have only been postulated but not directly observed.

DOI: https://doi.org/10.3850/IAHR-39WC252171192022453

Year: 2022