Experimental Analogue Modeling of Slope Dynamics Induced by Gradual River Incision Using a Controlled Suction Nozzle in Dry Sandbox Experiments

Progressive slope steepening can trigger episodic dry sand avalanches, resembling landslides commonly observed in natural environments. Similarly, gradual river incision can induce periodic slope instability and failures. To thoroughly investigate the impact of gradual river incision on catchment topography and slope dynamics, we conduct a series of idealized dry sandbox experiments. This simple setup is expected to provide a deeper understanding of the patterns and dynamics of landslides in mountainous regions.

In the experiments, dry sand is removed by applying negative suction pressure through a nozzle traversing prescribed paths over the topography. This process simulates river channel incision into the sand substrate and triggers avalanches on adjacent slopes. The experimental setup consists of a simple box filled with dry sand, equipped with a suction mechanism inspired by the extrusion nozzles used in 3D printing. Unlike 3D printing, where material is added, negative pressure at the nozzle is used to extract material instead.

To validate the system, we first employ a vertically descending suction nozzle at a controlled rate to produce an expanding conical pit. This simple setup allows us to test the suction mechanism and ensure consistent material removal. Subsequently, we simulate river incision by utilizing an idealized curved path designed to mimic the geometry of an incising river. Initially, the nozzle was manually guided along this path to replicate the incision process. In later experiments, a computer-controlled traversing system is implemented to ensure greater precision and reproducibility.

We then explore imposed motions along the main river channel and incorporate tributaries to explore the river incision processes. The results, including the formation of ridges, avalanches, and slope adjustments, are analyzed and compared with computational predictions derived from an eikonal model. This comparison provides valuable insights into the behavior of slopes under conditions of gradual river incision and elucidates the mechanisms driving slope instability and morphological evolution in natural catchments.