Abstract
Hydrologic and hydraulic variables common to many graphics. water resources engineering problems are known to contain considerable uncertainty. The description of the underlying uncertainty of these parameters is extremely important for the reliability of the analysis results. Uncertainty analysis should be adopted as another important step within the hydrologic and hydraulic analysis. Unfortunately, the incorporation of uncertainty analysis in many engineering studies is not a common practice due to lack of knowledge of its importance or just reluctance to recognize its validity. Traditionally, uncertainty associated with engineering problems has been treated indirectly through the application of safety factors or the consideration of the worst case scenarios. This research presents a methodology to explicitly account for the uncertainty associated with hydrologic and hydraulic variables during the analysis. A case study was performed on a local watershed where the physical system was estimated and analyzed. The developed methodology involves the use of conventional approaches to perform hydrologic and hydraulic analysis as well as a statistical procedure utilized to describe and quantify the underlying uncertainty in the analysis. Typically, in a hydrologic analysis a flow discharge is calculated at the outlet of a basin. Unfortunately, this discharge could change due to the presence of uncertainty in its computation. As with hydrology, in a hydraulic analysis a determined value of the water surface elevation at a certain location is calculated using the flow discharge obtained from the hydrologic analysis. Due to the inherent uncertainty in the hydrologic as well as in the hydraulic analysis that elevation could be higher or lower than the actual elevation calculated. Based on the case study and through the developed methodology, it was possible to develop stage and discharge frequency curves at selected locations along the channel. These frequency curves allow the analyst to see a range of possible discharges and a range of possible water surface elevations with their associated probability of occurrence at a specific location.
Vargas-Cruz, Ruben F. (1998). Dealing with parameter uncertainty in the calculation of water surface profiles. Master's thesis, Texas A&M University. Available electronically from
https : / /hdl .handle .net /1969 .1 /ETD -TAMU -1998 -THESIS -V37.