Abstract Description: Probabilistic Flood Hazard Analysis (PFHA) is traditionally applied to estimate hydrologic loading that may initiate dam failure mechanisms such as overtopping. Separate event tree models are often utilized to estimate the probabilities of downstream flooding that include dam breaches. However, the PFHA framework can be extended to explicitly include event tree model, enabling direct evaluation of the probability of breach and its resulting downstream flood hazards within a single, integrated analysis. This approach provides an efficient means of characterizing combined flood and breach risks to infrastructure and communities downstream of dams.
This presentation describes PFHA frameworks developed for two case studies: Idaho National Laboratory (INL) and New Brunswick Power’s Mactaquac Dam. It will highlight the key inputs and modeling components used to represent breach initiation and outflow. A central challenge in this application is defining the conditional probability of dam failure given a hydrologic loading condition. The case studies demonstrate that explicitly incorporating dam failure probability into PFHA can significantly alter downstream hazard curves, frequently identifying breach scenarios as the primary contributors to extreme flow probabilities. The results illustrate a practical and defensible method for integrating conditional dam failure probability and breach hydraulics into a PFHA.
Learning Objectives:
Learn general knowledge about PFHA including inputs, outputs and uncertainty consideration.
Demonstrate methods to incorporate conditional probability of dam failure into PFHAs.
Discuss impacts of dam failure on downstream infrastructure in PFHA.
