In January, the USGS released a report detailing a scenario similar to a series of storms that struck California in the winter of 1861-1862 when rain fell for 45 days and turned the Central Valley, a vast area of approximately 42,000 square miles in the middle of the state, into an inland sea. Proposing that a similar storm could happen again, the report details the effects of the rainfall, as well as its impact on human life, the economy, the environment and infrastructure across the state.
“What I’m hoping is that we’re seeing the federal government really wake up to it and kind of moving away from this kind of total focus on terrorism,” said Ronald Baldwin, director of emergency operations for the San Joaquin County Office of Emergency Services. “Not that they can’t continue with that, but also then put some more significant efforts into flood planning.”
State and local flood control officials questioned the report’s conclusion that the 1861-1862 storms would create similar damage, saying it ignores the flood protection infrastructure and response plans that have been put in place over the last 150 years. “We now have the capability to put [the water] into downstream reservoirs through the Central Valley Project and through the State Water Project,” said Sonny Fong, emergency preparedness and security manager at the California Department of Water Resources. “So we can alleviate a sizable amount of the pressure from heavy flows.”
Dams would not break, according to Fong, but infrastructure at ground level would be flooded.
The report probably won’t change what flood managers are doing to address the risk, but Baldwin and Fong think the scenario could attract the attention of elected officials and the public to provide greater support for mitigation efforts.
One of the things Baldwin would like to see is the establishment of a national institute that would further professionalize flood prevention and response. “Firefighters have national institutes and stuff,” Baldwin said. “We don’t have anything as far as a national center to take a look at how we could better fight these floods and do things to reduce losses in floods.”
The ARkStorm scenario was released at a summit in mid-January in Sacramento during which more than 100 flood prevention experts from across federal, state and local government and the private sector came together to discuss flood prevention and recovery. It reinforced the need to continually move forward on improvements to the state’s flood control system and the need to be able to provide advanced intelligence to local decision-makers so they can use that information to implement their plans, Fong said.
The summit was organized after the USGS presented the ARkStorm scenario to the California Emergency Management Agency (Cal EMA) and proposed doing a statewide exercise series around it. Local emergency managers said they weren’t prepared to participate in an exercise of that scale, so a separate event was organized. “The summit has identified the seriousness of the threat to the point where we’re going to work with FEMA on a catastrophic incident concept of operations for the San Joaquin Delta,” said Jim Brown, inland regional administrator for Cal EMA. That effort would be similar to the memorandum of understanding the two agencies recently reached regarding earthquakes in Southern California.
Cal EMA is also working with the U.S. Army Corps of Engineers to get counties to develop contingency maps like those that San Joaquin County produced. The maps include: locations where levees may breach; freeway elevations; evacuation collection and deposit points; helipad locations; school, hospital and nursing home locations; and levee patrol plans.
The summit followed an ARkStorm tabletop exercise in October 2010 that included federal, state and local government representatives and private-sector stakeholders.
The ARkStorm scenario was designed by a team of scientists working with the Multi Hazards Demonstration Project (MHDP) at the USGS to approximate the storms California experienced in the winter of 1861-62. The model places two historic storms from January 1969 and February 1987 back to back in a scientifically plausible way. Those two storms were examples of atmospheric rivers, storms that draw heat and moisture from the tropical Pacific and then pour a warm rain on the West Coast over several weeks.
“The ARkStorms are different from hurricanes in that they’re primarily winter phenomena and the wind and the rain are not as well coupled,” said Lucy Jones, ARkStorm architect and chief scientist at the MHDP, in a podcast. “So they’re primarily flooding events, but they’re capable of huge levels of damage, and that’s what we wanted to look at in this project.”
Damages from ARkStorm-level rains, including business interruption costs, are estimated to cost $725 billion — about four times the damage estimates from a 100-year earthquake along the San Andreas Fault. It’s estimated that the flood would require the evacuation of 1.5 million people and damage one-quarter of the houses in California. It’s also estimated that the resulting flooding would cause thousands of landslides.
To better define ARkStorm’s impacts, the USGS and California Geological Survey have also developed a scale to describe the severity of landslides that classifies the rock in various areas as either hard rock, soft rock or soil then takes into account the degree of slope in a particular area to calculate landslide susceptibility.
Another outcome of this project is the furthering of a common nomenclature for West Coast winter storms because there’s no scale on which to measure their intensity.
How do you plan to use the ARkStorm scenario? Join the discussion on Emergency Management’s Facebook page.
