Verification of Hydraulic Parameters of Nature-like Fish Pass

Abstract

Nature-like fish passes are commonly designed as a preferred way to overcome barriers in rivers. However, meeting the recommended hydraulic parameters for these passes can be challenging. As a result, boulders or sills are often incorporated to supplement their structure. From a hydraulic standpoint, the crucial parameters under investigation are the depths and velocities (or the corresponding velocity field). In this study, a comprehensive analysis was conducted on a full-width rock-ramp fish pass constructed in a river, specifically targeting the barbel zone. The achieved parameters were assessed through direct field measurements, complemented by mathematical modeling using 1D and 2D HEC-RAS models (version 6.3.1). For the assessment of model accuracy, the error indices root mean square error (RMSE) and mean absolute error (MAE) were used. Based on their evaluation, the 1D model provides more precise results in the assessed profiles (the RMSE for depths (m) was 0.0663 (for velocities (m∙s−1) 0.293) compared to the 2D model, where the RMSE for depths (m) was 0.070 (for velocities (m∙s−1) 0.398), the MAE for the 1D model for depths (m) was 0.0350 (for velocities (m∙s−1) 0.185) compared to the 2D model, where the MAE for depths (m) was 0.0375 (for velocities (m∙s−1) 0.274)). The findings highlight the differences in the problem-solving approaches between the models as well as the potential for simplifications in practical applications.