Measuring and modeling event-based environmental flows: An assessment of HEC-RAS 2D rain-on-grid simulations

There is an immediate need to use available modeling tools quantify environmental flows targets where changing climate and human activity has altered hydroecologically important streamflow regimes. A model performance assessment was undertaken using observed data collected from five nested gauging sites in a mixed land watershed of the central US. An integrated approach used couple The Soil Water Assessment Tool (SWAT version 2012), Hydrologic Engineering Center's River Analysis System (HEC-RAS 5.0.7). SWAT generate effective rainfall needed run HEC-RAS rain-on-grid two-dimensional hydrodynamic simulations. Model calibration results showed potential usefulness coupling approach. For example, PBIAS 8.3%, NSE value 0.84, coefficient determination (R2) 0.80 at highly urbanized monitoring site for calibration. Split-site validation values that ranged 10.4 33.8%, 0.33 0.92, R2 0.86 0.97. Results 2D simulations can produce realistic stage hydrograph response when: (1) areal precipitation forcing's, (2) calibrated during event interest, (3) there are not substantial sources backwatering outside models geometric data, (4) saturated antecedent soil moisture conditions surface DEM's adequately describe overland flow paths. This among first, if show associated with scale. highlight time-varying roughness coefficients account conditions, point efficacy SWAT/HEC-RAS event-based information.