A storm event watershed model for surface runoff based on 2D fully dynamic wave equations

Abstract

The main purpose of this work concerns the development and testing of an overland flow model based on the two‐dimensional fully dynamic shallow water equations. Three key aspects, fundamental to get accurate, efficient and robust computation of surface runoff at basin scale, are discussed by transferring the main findings obtained by the recent research on the topic of dam‐break wave and flood propagation in the context of rainfall–runoff modelling. In particular, attention is focused on the numerical flux and bottom slope source terms computation, on a numerical treatment of friction slope terms and on an algorithm for dealing with wetting/drying fronts. The performances of the numerical model have been preliminarily evaluated using experimental or ideal tests characterized by very critical conditions for the stability of a numerical model. Then, attention was focused on a real event occurred in a sub‐basin of Reno river in Italy to analyse the suitability of the model in simulating real flood situations. The numerical results highlight the good performances of the model in all the simulations discussed in the paper. Copyright © 2012 John Wiley & Sons, Ltd.

Estimating the microbiological risks associated with inland flood events: Bridging theory and models of pathogen transport

“…Furthermore, areas affected by overbank flows or heavy rainfall may exhibit markedly altered pathogen mobilization and transport, due to the activation of preferential flow pathways and decreased retention of transported pathogens in the surface layers of saturated soils (Bradford, et al 2013). Meanwhile, flooding can give rise to variations in flow depth and velocity beyond what would be experienced under normal conditions, due to greater in-channel flow volume relative to the wetted perimeter, variable depth, width, and direction of flow across inundated areas, and complex transfers of momentum between areas of deeper and shallower flow (Costabile, et al 2013, Ikeda and McEwan 2009, Nittrouer, et al 2011). In addition, backwater effects can occur along flooded channels or across inundated areas, where alterations of upstream flow characteristics are induced by downstream obstructions (e.g., rising waters become partially obstructed by a bridge), or transitions to sub-critical flow regimes (Ikeda and McEwan 2009).…”

“…The complete form of the momentum equation given above (eqn 2), also known as the dynamic wave equation, is capable of modeling fully unsteady (time-varying), non-uniform (space-varying) flows, including the effect of downstream conditions on upstream depth and flow velocity (i.e., backwater effects). The dynamic wave equation is considered the standard of physical fidelity for conservation of momentum, especially when modeling overbank flows and sediment transport using high-resolution topographical data (Costabile, et al 2013). …”

Enhancing river model set-up for 2-D dynamic flood modelling

“…A possible way to overcome these problems could be the use, at the catchment scale, of the shallow water equations modified in such a way to receive rainfall as input and linked with a specific module for the computation of the infiltration losses. Though this is a quite ambitious strategy, there are some recent papers in the literature that are moving in this direction (da Paz et al, 2011;Caviedes-Voulli eme et al, 2012;Costabile et al, 2013;Paiva et al, 2013;Werner et al, 2013).…”

A new efficient implicit scheme for discretising the stiff friction terms in the shallow water equations

“…To provide stable simulations, implicit schemes have been widely used to discretise the friction source terms (e.g. Fiedler and Ramirez, 2000;Liang et al, 2007;Cea et al, 2010;Song et al, 2011;Costabile et al, 2013;Simons et al, 2014;Busaman et al, 2015;Cea and Blade, 2015;Rousseau et al, 2015;Singh et al, 2015 ). Unlike the explicit schemes, implicit schemes use the velocities at the new time step to evaluate the friction terms.…”

“…Other researchers (e.g. Liang et al, 2007;Cea et al, 2010;Song et al, 2011;Costabile et al, 2013;Busaman et al, 2015;Cea and Blade, 2015;Rousseau et al, 2015;Singh et al, 2015 ) express the friction terms as the product of the velocity in the current time step and that in the new time step to obtain an explicit formula. Although these schemes may effectively avoid the numerical instability caused by the stiff friction terms, they commonly relax the flows to a wrong steady state, which may consequently lead to incorrect simulation results ( Xia et al, 2017 ).…”