flexBMDM: a biomorphodynamic model using vegetation models (vegetation friction subroutines)
Summary
Vegetation significantly influences flow and sediment transport dynamics. To represent these processes numerically in openTELEMAC, a biomorphodynamic model has been implemented by Li et al. (2020). The existing biomorphodynamic model (branch: vegetation) applies a drag force approach for rigid cylinders and the sediment transport adjustment method of Bonilla-Porras et al. (2021). We enhanced the existing biomorphodynamic model by substituting the drag force approach with vegetation models implemented by Frederik Folke. Besides that, the model was restructured in a modular framework so that extensions regarding vegetation models or sediment transport adjustment methods are easily achievable. The method of inputting data is now done by defining the parameters in an ASCII file instead of using user Fortran subroutines. This enhancement improves the user- and developer-friendliness. This concernes the TELEMAC-2D and GAIA module.
Why is this feature useful?
The enhanced biomorphodynamic model (flexBMDM) improves user accessibility by eliminating hardcoding requirements. It also provides flexible options for defining vegetation and sediment transport parameters, such as the ability to adjust for different types of vegetation and varying flow conditions by defining different vegetation models. Thus, this framework allows for more precise and user-friendly simulations of sediment dynamics influenced by vegetation.
How to implement it?
For implementing the flexBMDM, subroutines already modified by Li et al. (2020) are further adjusted. Besides that, subroutines regarding vegetation friction are adjusted. To ensure consistency, subroutines using the total bed shear stress TOB also need to be adjusted to eliminate the vegetation friction component from these parameters (concerning slope effect, secondary currents).
Additional resources
The flexBMDM has already been described by Dallmeier et al. (2024). The model is tested using five laboratory experiments by Armanini and Cavedon (2019).
References: Armanini, A. & Cavedon, V. (2019): Bedload through emergent vegetation. Advances in Water Resources, 129: 250–259. DOI: 10.1016/j.advwatres.2019.05.021. Bonilla-Porras, J. A.; Armanini, A.; Crosato, A. (2021): Extended Einstein's parameters to include vegetation in existing bedload predictors. Advances in Water Resources, 152: 103928. DOI: 10.1016/j.advwatres.2021.103928. Dallmeier, Antonia; Kopmann, Rebekka; Folke, Frederik; Schwedhelm, Hannah; Rüther, Nils (2024): Modeling the Effect of Vegetation on Sediment Transport: a User-Friendly Implementation. In: Proceedings of the XXXth TELEMAC User Conference, Chambéry, 8-9 October 2024. Li, J.; Claude, N.; Tassi, P.; Cordier, F.; Crosato, A.; Rodrigues, S. (2020): Implementation of a novel approach accounting for the influence of vegetation on sediment transport in GAIA. A. Breugem, L. Frederickx, T. Koutrouveli, K. Chu, R. Kulkarni und B. Decrop (eds), Online proceedings of the papers submitted to the 2020 TELEMAC-MASCARET User Conference October 2020. 2-8. Antwerp: International Marine & Dredging Consultants (IMDC).