Escape from the Delta: preparation and evacuation for catastrophic flooding in California Emergency Management Agency Region IV

Abstract

We model the regional highway system of Central California and consider the challenge of evacuating a highly populated region from the threat of catastrophic flood. Specifically, we build a minimum cost network flow problem to represent the movement of more than one million people within Yolo, Sacramento, San Joaquin, and Stanislaus Counties. Our model solves for "best case" evacuation routes and clearing times assuming perfect knowledge of flood inundation and road conditions. Our model is large but efficient, solving 35 separate scenarios in less than 45 minutes. We develop two basic evacuation scenarios, each having many variations, resulting in 490 total scenarios. For these, we analyze model assumptions and the effect of interruptions to evacuation behavior for a range of "what-if" situations.