Table 2 Modeling characteristics of 1D and 2D in HEC-RAS for datasets 1 and 2.
From: Multidimensional Datasets Supporting Vulnerability Assessments of Riverine Bridges in Peru
Characteristics | HEC-RAS 1D | HEC-RAS 2D | Data set 1 (1D) | Data set 2 (1D) | Data set 2 (2D) |
|---|---|---|---|---|---|
Mathematical formulation | 1D Saint-Venant equations (continuity and momentum). | 2D Saint-Venant equations (shallow water equations). | Continuity and momentum | Continuity and momentum | SWE-EM (Stricter Momentum) |
Main dependent variable | Discharge Q(x,t) and water depth h(x,t). | Water depth h(x,y,t) and velocities \(u\) (x,y,t), \(\upsilon \) (x,y,t) | Steady flow with discharges of T = 100 (247.5 m³/s), T = 140 (259.3), T = 200 (271.5 m³/s) and T = 500 (301.9 m³/s) years. | Steady flow with discharges of T = 50 (223 m³/s), T = 100 (248.5 m³/s), T = 200 (273 m³/s) and T = 500 (304.3 m³/s) years | Unsteady flow for discharges of T = 50, T = 100, T = 200, and T = 500 years |
Flow direction | Flow restricted to the longitudinal direction of the channel. | Free flow in two horizontal directions (x,y). | 135 cross-sections | 321 cross-sections perpendicular to the channel axis | — |
Geometric representation | River profile through cross-sections perpendicular to the channel axis. | 2D mesh that discretizes the entire floodplain. | — | — | 9503 cells Spacing DX = 5 m Spacing DY = 5 m |
Represented processes | Water levels and discharges along the channel axis. Handles structures (bridges). | Spatial flow dynamics: overflows, recirculation zones, floodplain flows. | Contraction coefficient (0.3), expansion (0.5), dredging (Cd = 1.33), and semicircular pier shape (K = 0.9) | Contraction coefficient (0.3), expansion (0.5), dredging (Cd = 1.33), and semicircular pier shape (K = 0.9) | Overflows, recirculation zones, floodplain flows |
Boundary conditions | Defined at upstream and downstream cross-sections. | Defined at the upstream and downstream mesh boundaries. | Mixed flow (Normal Depth) for subcritical and supercritical flow | Mixed flow (Normal Depth) for subcritical and supercritical flow | Upstream and downstream (BClines) |
Numerical resolution | Implicit finite difference scheme at discrete sections. | Finite volume method with conservative flow solution in cells. | Finite difference method (FDM) | Finite difference method (FDM) | Finite volume method (FVM) |
Computational requirements | Low memory and computational time requirements. | High computational demand (depends on mesh size and refinement). | AMD Ryzen 7 5800H with Radeon Graphics | 13th Gen Intel(R) Core (TM) i7-13650HX | AMD Ryzen 7 5800H with Radeon Graphics |
Limitations | Does not adequately represent lateral flows, recirculations, or complex overflows. | High demand for topographic data and simulation times. | Discrete cross-section, linear, simplified floodplain | Discrete cross-section, linear, simplified floodplain | DTM (DJI Phantom 4 RTK drone, every meter) and time step based on Courant criterion (1 s) |
