Sensitivity Analysis on Water Surface Profiles Generated from Hydrodynamic Modelling with Respect to Inaccuracy of Cross-section Data

Abstract

Computer aided Hydrodynamic Modelling has become a convenient tool in modem-day with the development of separate hydraulic analysis components attached to multi-user networks with graphical user interfaces. Generated outputs from hydrodynamic models are used to predict engineering design parameters and to check hydraulic designs. Hence, model calibrations and verifications are performed, in order to assess and confirm the reliability of generated outputs. Accuracy of the input data significantly affects the model reliability. Although, the achievement of high degree of accuracy for hydraulic engineering parameters during data collection process is unlikely, careful scrutinisation and prompt attempt to identify the inaccuracies even in the order of magnitude can certainly enhance model performance and reliability. To study the influence of inaccurate input data to the model performance, inaccurate data were purposely included for previously calibrated and verified models. The said calibrated and verified models were developed by the authors for case studies of stormwater drainage analysis for Colombo-Katunayake Expressway at Kalu Oya intersection and for Southern Transportation Development Project at Welipenna intersection. The present work describes the sensitivity of generated outputs and specially the water surface profile with respect to inclusion of three inaccurate cross-sections for each model. Further, percentage errors of cross-sections were discreetly varied as +50%,+ 35%,+25%,-25%,-35% and -50% to study the influence. Additionally, individual effect for inaccurate cross-sections and combined effect for selected and amalgamated inaccurate cross-sections were studied. For the considered range in percentage error of input data, results indicate that water surface profile varies -15% to 30%.