UNCERTAINTY AND SENSITIVITY ANALYSES OF PIT-MIGRATION MODEL

Abstract

Sand and gravel mining from a river bed results in irregular pits on the river bed. The migration of the pits might potentially threaten the safety of downstream bridge piers and other in-stream hydraulic structures. Models were developed to simulate the movement of pits for predicting the effect of migrating pits on in-stream structures. In view of random characteristics inherently residing in hydraulic and hydrologic processes, it is essential for an engineer to assess the overall uncertainty features of a hydraulic model output subjected to its stochastic input parameters. As an illustration, this paper analyzes the uncertainties of a pit migration model recently proposed by Lee et al. (1990) using three methods including the first-order variance estimation method, point estimation technique, and Latin hypercubic sampling. Comparisons of merits and limitations of these methods are also made.