Abstract
An advection-diffusion model is proposed to simulate large wood transport during high flows. The mathematical model is derived from the wood mass balance, taking into consideration both the wood mass concentration and the log orientation, which affects log transport and, most importantly, wood accumulation. Focusing on wood mass transport, the advection-diffusion equation is implemented in a hydrodynamic model to provide a one-way coupled solution of the flow and of the floating wood mass. The model is tested on a large series of flume experiments, involving at least 30 logs and different control parameters (flow Froude number, log length, diameter, release point). The validation through the experimental data shows that the proposed model can predict the correct displacement of the most probable position of the logs and to simulate with a sufficient accuracy the planar diffusion of the wooden mass. Transversal wood distribution is more accurate than the streamwise one, indicating that a higher control on the longitudinal diffusion needs to be implemented.
Highlights
Rivers are important components of urban settings
Flood hazard maps are a fundamental tool for this purpose, since they help in identifying which areas are at risk and to what extent planned measures are effective
The total mass of the logs is treated as a passive and conservative substance, so that an advection-diffusion equation is numerically coupled with the SWE, allowing for the coupled solution of the water flow and the Large Wood (LW) transport. This solution prevents the acquisition of detailed information about LW pieces that are substituted by the total mass of wood observed, or expected, during a flood. In this contribution (i) the mathematical model outlined in [30] is discussed, and the advection-diffusion equation for wood mass transport is implemented in the twodimensional code ORSA2D [31]; (ii) the main parameters of the advection-diffusion equation, i.e., the transport velocity and the diffusion coefficients, are calibrated to the typical situation of large wood thanks to the analysis of available experimental campaigns [30] and, (iii) the performances of the proposed model are evaluated against flume experiments [30,32], providing a global measurement of how the model can replicate LW transport
Summary
Rivers are important components of urban settings. In the past, human relied on rivers for protection and livelihood while presently their role is mainly related to social and ecological benefits, through several revitalization projects all around Europe [1]. Different models including Large Wood (LW) transport in hydraulic simulations were developed Taking their cue from the mathematical analysis of Braudrick and Grant [15], existing models consider each log as a single element which can be entrained, transported, and deposited by the flow. Since several elements can be transported during a flood and each one needs to be considered in a Lagrangian framework, simulation times can grow owing to the large number of operations required to compute individual trajectories and mutual interactions Such deterministic approach is not fully representative of a stochastic phenomenon such as LW transport. In this contribution (i) the mathematical model outlined in [30] is discussed, and the advection-diffusion equation for wood mass transport is implemented in the twodimensional code ORSA2D [31]; (ii) the main parameters of the advection-diffusion equation, i.e., the transport velocity and the diffusion coefficients, are calibrated to the typical situation of large wood thanks to the analysis of available experimental campaigns [30] and, (iii) the performances of the proposed model are evaluated against flume experiments [30,32], providing a global measurement of how the model can replicate LW transport
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
