Accuracy Assessment of the HEC-RAS 1D Model for Simulating Flow Through Aquatic Vegetation and Obstructions Using Laboratory Open Channel Experiments

Abstract

Flooding represents a severe natural disaster with impacts on human lives and property in numerous regions, affecting both urban and rural areas. Hydraulic models serve as essential tools for water management and preventive planning, requiring accuracy and reliability to analyze and evaluate water flow behavior under various scenarios, thereby systematically supporting engineering decisions and risk management strategies. This research focuses on examining the accuracy of the one-dimensional Hydrologic Engineering Center - River Analysis System (HEC-RAS) model in predicting water flow behavior in open channels containing submerged vegetation and obstructions. The study compares model predictions against results from physical laboratory experiments simulating flow conditions to develop a clear understanding of the model's limitations and potential for practical applications. The experimental methodology involved measuring water levels and flow velocities in conditions with obstructions and simulated structures, then comparing these measurements with values calculated using the HEC-RAS model. Results indicate that the model demonstrated a high level of accuracy in predicting water surface levels across all cases, with NSE values ranging from 0.93 to 0.99. It also showed good accuracy in predicting flow velocity, with the lowest NSE value of 0.62 observed in the bare channel case and the highest value of 0.87 in the artificial grass case. The variability is attributed to the challenges in measuring flow velocity in laboratory conditions due to the turbulent nature of the flow. Therefore, the approach presented in this study can serve as a solid foundation for evaluating and developing models for water management in areas with aquatic vegetation or natural flow obstructions in the future.