Representation of Vegetation in Two-Dimensional Hydrodynamic Models

Abstract

Herein we present the work product from an ASCE Task Committee charged with providing a succinct review of the available approaches for determining flow resistance coefficients for vegetated floodplains for use in two-dimensional hydrodynamic model simulations, with comparison of the most promising approaches. In the future, with the restoration and conservation of ecosystems of growing importance, engineers will increasingly design and manipulate floodplain vegetation. Conceivably, the appropriate placement of plants along stream corridors may direct overbank flows, improve flood storage, reduce scour and erosion, facilitate sediment transport, and alleviate other flood risk factors, while also providing critical habitat. Previous approaches to predicting water surface elevations along vegetated channels and floodplains consisted of running computer models that typically allowed little temporal variation in flow resistance coefficients during the course of a flow event. More recently, the sophistication of flow models has improved to allow simulation of interactions among hydraulic variables and vegetation properties. The literature dealing with the effects of vegetation on open channel flow is vast and growing. Several workers have reviewed the current state of the science (Montakhab et al. 2012; Curran and Hession 2013; Hession and Curran 2013; Dombroski 2014, Zahidi et al. 2014), and the paper by Aberle and Jarvela (2013) summarizes the state-ofthe-art in research on the flow resistance of emergent rigid and flexible floodplain vegetation. This paper compiles and interprets this recent literature, with an focus on the estimation of vegetated floodplain resistance for two-dimensional numerical modeling.