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A Case study for calculating and reporting the uncertainty budget of 1 and 2 dimensional combined hydraulic model

Gül, Uğraş Sidar
This study aims to suggest a framework to quantify and report the uncertainty budget of a 1 & 2 dimensional hydraulic model of five possible error sources by using ISO GUM method. The river engineers take into account several considerations when they design the riverbeds; one of the main considerations is the flood protection aspect of the riverbed, to asses that a hydraulic model is usually prepared. However, results generated from the hydraulic models are not exempt from errors. The ISO GUM method provides guidelines and specifications to express combined uncertainties to quantify and report these errors. The reference model -which is derived from a case study in Kemalpaşa, Artvin Turkey- lies in the center of data generation. Treating the reference model as a laboratory, by manipulating the reference model with custom VBA codes and exporting result with Python codes, an extensive set of data from 3825 model runs were generated for five error sources. The measurement in this study is the maximum water surface levels in meters. As a result, the uncertainty budgets of 16 cross sections and 14 two-dimensional computational cells were calculated. It is foreseen that the variations in input parameters result in a maximum combined uncertainty of ± 0.454 m for cross sections and ± 0.664 m for 2-dimensional computational cells at 95% confidence level with coverage factor of 1.96 . It would be safe to say that the majority of the error is due to the variation in Manning’s n coefficient.