Evaluating the Applicability of a Two‐dimensional Flow Model of a Highly Heterogeneous Domain to Flow and Environmental Management

Abstract

Two‐dimensional simulation of highly heterogeneous domains, especially those with disparate length scales, roughness conditions, and geometries, often leads to challenges such as long computation times and numerical instability. Simulation of challenging domains is often needed to guide flood management and environmental regulation agencies in operation and potential domain modifications. This work evaluates the ability of a two‐dimensional unsteady hydrodynamic model to represent long‐duration transient flows over a domain with highly heterogeneous roughness, geometric characteristics, and length scales through bed roughness representation. The domain includes 13 km of Cache Creek and the 14.5 km2 Cache Creek Settling Basin, which traps both sediment and mercury. Calibration under different bed roughness methods, validation, and modeling results of bathymetric modification scenarios are presented. The modeling approach's performance supports its application as a tool for management of similar domains, such as settling basins, leveed floodplains, and reservoirs. Accurate representation of flow dynamics can also inform environmental management that involves transport of sediments, nutrients, and heavy metals. This study found that a two‐dimensional unsteady flow model can accurately represent long‐duration transient flow in a large settling basin with highly heterogeneous characteristics without parsing of the domain or flow events simulated.

Optimizing the riparian zone width near a river for controlling lateral migration of irrigation water and solutes

“…However, their study unravelled the impacts of groundwater pumping on salinization risks of a flood plain. Similarly, Carr et al (2018) calibrated and validated a 2D model on gauged groundwater elevations and hypothesized that the accurate representation of flow dynamics can inform environmental management involving transport of sediments, nutrients, and heavy metals. Other studies also have used similar approaches (e.g., Rousseau et al, 2012).…”

Fuzzy map comparisons enable objective hydro‐morphodynamic model validation

“…Model calibration of hydrodynamic parameters builds on measured hydraulic parameters such as flow velocity and water depth compared with modeled values. For example, if the modeled water depth is generally lower than the observed water depth, the roughness value to be used with the numerical model is iteratively adapted until a best global match between modeled and observed data is achieved (e.g., Barker et al, 2018;Carr et al, 2018). Morphodynamic model parameters are, for instance, the Shields (1936) parameter (also referred to as critical dimensionless bed shear stress), which is vetted in the calibration process against observed elevation (i.e., topographic) change rates.…”