Regional Mountain Conference

High mountain Alpine lakes are fundamental systems, as they provide essential ecosystem services. In glacierized catchments, they play a crucial role in regulating sediment transfer, trapping and redistributing melt-derived suspended sediments. In recent year they have become increasingly exposed to multiple environmental pressures, such as climate-driven hydrological shifts and glacier retreat, processes that alter sediment delivery. Hence, being able to model sediments dynamics become essential for anticipating ecosystem evolution and assessing how these systems respond to changing environmental forcings. Yet most of the existing hydrodynamic models are designed for large and stratified basins, not adequate for the cold-monomictic lakes typical of high altitude environments.

In our study, we present a simplified, dimensionless and radially symmetric 2D model for the sediment transport and deposition in non stratified Alpine lakes. The formulation is based on mass conservation applied to water and suspended sediment independently. To close the problem, an analytical expression for bed sediment flux has been derived through a perturbative expansion of the advection–diffusion equation in cylindrical coordinates. The resulting model is simple, fully replicable, requires a limited amount of input data, and does not need calibration.

We tested the model with both real data, collected at the Seracchi Lake (Western Italian Alps), and synthetic inputs, generated through sinusoidal forcing. Despite its simplified structure, the model effectively reproduces the observed dynamics of suspended sediment. Sensitivity analyses highlight the dominant role of the reference vertical flux, indicating that settling velocity and lake geometry exert the strongest control on model output, while the effect of grain size emerges naturally through settling velocity.

The model’s responsiveness to hydrological inputs and basin characteristics demonstrates its potential for estimating annual sediment fluxes and assessing the evolution of trapping efficiency under shifting forcings on short time scales. The analytical expression derived for bed flux also supports the estimation of annual deposition and long-term infilling dynamics, enabling the identification of silting time and predicting when a lake may transition toward a peat-forming system, with implications for its ecological function.