The U.S. Geological Survey has just released a report from their two-year Multi Hazards Demonstration Project (MHDP) that outlines California’s vulnerability to a major winter storm termed an ‘atmospheric river’ that would produce precipitation that could devastate the central valley of the state. Such a storm hit the region in the winter of 1861 and 1862 and made much of the valley impassable. Given current populations, this once in 500 to 1,000-year event would have dramatic impacts the population, infrastructure and economy.
A multidisciplinary team made up of scientists, engineers, policy experts, insurers and service providers pulled together the ARkStorm scenario with realistic models of meteorological events, and a modeling of secondary hazards such as landslides and flooding. The extreme flooding scenario is at a level that can’t be accommodated by the state’s flood-protection system, with flooding 300 miles long and 20 or more miles wide. An ARkStorm could cost on the order of $725 billion, with devastating impacts to agriculture, property, productivity, and infrastructure. Evacuation from floodwaters could include 1.5 million residents.
This exercise is meant to drive preparedness and to inform policy, prompting serious debate about investing now in mitigation measures rather than suffering a devastating bill later.
