ASCE-EWRI 2009 – World Environmental Water Resources Congress Developing Probability of Failure Estimates for Stream Restoration Design Components

摘要

Stream restoration projects are proliferating in all regions of the country to provideimprovements to streams disturbed by highway construction, urbanization, andchannel modifications. The morphologically-based natural channel design method iscommonly used to design stream restoration projects; however, the designapproach is often vague, qualitative, and lacking in guidance. This can lead to anincrease in project uncertainty and costs. A two-step method of incorporatinguncertainty and risk in stream restoration design has been developed as acombination of Design Failure Modes and Effects Analysis (DFMEA) and riskquantification. The purpose of DFMEA is to prioritize failures in accordance withtheir risk. The definition of risk contains two components: (1) probability of failureand (2) consequence of failure. Probability of failure of stream restoration designcomponents is often difficult to determine due to lack of published failure data. Inthe existing risk assessment method, the likelihood of occurrence ratings from theDFMEA are used to estimate the probability of failure. A set of tasks were carriedout to improve the application of the two-step risk assessment method bydeveloping better estimates of probability of failure for stream restoration designcomponents. A literature review was performed to compile potential failure modes,causes of failure, associated predictor variables, and uncertainty in the predictorvariables for stream restoration design components. Following this, advancedprobabilistic techniques, namely Logistic Regression Analysis (LRA) and Monte Carlo