Effects of advection on predicting construction debris for vulnerability assessment under multi-hazard earthquake and tsunami

Abstract

Post survey results from devastating events such as the 2010 Chile and 2011 Tohoku earthquake and tsunami reported that different types of debris could be generated and shifted landward during tsunami inundation. That advected debris can result in significant damage to structures and negative impacts on community resilience during the recovery process. To improve mitigation plans, minimize losses, and to improve the community resilience to future tsunami events, it is necessary to quantify the debris and predict its final distribution. In this study, we present a framework to quantify the amount and location of construction debris generated and advected from a multi-hazard earthquake and tsunami event. The framework performs fragility analysis based on maximum intensity measures of the hazards, quantifies the amount of debris, and then advects the buoyant portion of debris using a time-dependent inundation model to estimate the trajectory and final distribution of debris. We apply this framework to Seaside, Oregon, subjects to events from the Cascadia Subduction Zone for eight recurrence intervals over the range of 100 to 10,000 years. Comparison of the debris distribution with and without the advection model highlights the importance of including advection to understand the final debris distribution. We show that the final debris distribution could have a significant impact on the initial accessibility and functionality of critical facilities which would be difficult to estimate considering the hazard intensity only. We show how the volume of debris generated and advected increases with the decreasing annual exceedance probability (increasing return period) and how the location of the peak cross-shore debris profile is related to the maximum limit of tsunami runup. This analysis considers only buoyant construction debris and could be extended to consider nonbuoyant, natural (e.g., vegetation) and anthropogenic (e.g., vehicles, shipping containers, marine vessels) debris.