Improved floodplain vegetation roughness for 1D hydraulic models

A. Crosato, J. Zulfan, Andrés Vargas-Luna

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1D hydraulic models are largely used to simulate the propagation of flood waves and for flood mapping along river systems. The most common approach to account for the hydraulic effects of vegetated floodplains consists of imposing higher roughness coefficients. However, the flow resistance of vegetation is governed by plant submergence, which is water-depth dependent and varies with the discharge, and thus with time. An improved method properly incorporating floodplain vegetation roughness in 1D models is presented here. The Manning coefficient is derived from a simplification of Baptist’s formula assuming horizontal floodplains, i.e., with the same water depth everywhere. Considering the dependency of vegetation roughness on local water depth (in case of variable flow conditions), a predictor-corrector approach of the derived formula is proposed to be applied at every computational time-step. If different types of vegetation are present, the roughness coefficient, one for each floodplain, is derived as a weighted average. The method is tested on a recently restored stream located in the Netherlands, the Lunterse Beek, using the HEC-RAS code. The results support the implementation of the proposed method, but validation is needed for river floodplains with non-uniform vegetation cover.
Original languageEnglish
Title of host publicationRiver Flow 2020
Subtitle of host publicationProceedings of the 10th Conference on Fluvial Hydraulics
EditorsW. Uijttewaal, M.J. Franca, D. Valero, V. Chavarrias, C.Y. Arbos, R. Schielen, A. Crosato
Place of PublicationLondon
PublisherCRC Press / Balkema - Taylor & Francis Group
Number of pages9
ISBN (Electronic)978-1-003-11095-8
ISBN (Print)978-0-367-62773-7
Publication statusPublished - 2020
EventRiver Flow 2020: The 10th Conference on Fluvial Hydraulics - Delft, Netherlands
Duration: 7 Jul 202010 Jul 2020


ConferenceRiver Flow 2020

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