Peter Gleick: Learning to Live with Floods

January 10, 2023

Peter Gleick in the Washington Post:

Peter H. Gleick is a hydroclimatologist, co-founder of the Pacific Institute and author of the forthcoming book “The Three Ages of Water.”

In November 1861, it began to rain in California, presaging disaster. By late December, the rivers were full, the Sierra Nevada was under snow, and the soils of the Central Valley were saturated. In early January 1862, storms delivered 10 feet of rain from the Columbia River to the Mexican border. The final blow fell in mid-January. Another intense storm — warm this time — swept in from the Pacific Ocean, melting the massive snowpack and sending more water cascading into the soaked Central Valley.

By the time the storms ended, devastation reigned. Millions of acres of land had become an inland sea. Thousands of people were dead. Some 200,000 cattle and more than half a million sheep drowned. New telegraph lines were lost, disrupting communications with the East, and 1 in 8 homes in the state was destroyed. In all, the so-called ARkStormwiped out an estimated quarter of the state’s economy.

It’s likely to happen again. Geological evidence suggests that six megastorms even more severe have occurred over the past 1,800 years. These events funnel moisture from the Pacific Ocean to the west coast on a scale far worse than the floods now hammering California.

California today is different than 160 years ago, of course. Then, the state’s population was around 500,000. Today, it exceeds 40 million. The Central Valley now produces one-quarter of the nation’s food and 40 percent of its fruits, nuts and vegetables. The cities of Sacramento, Fresno, Stockton and Bakersfield lie in the flood plains of major rivers, but massive reservoirs hold back and store floodwaters. Thousands of miles of levees protect low-lying areas and channel waters away from humans and property. And a sophisticated satellite observation and weather forecasting system provides remarkably accurate early warning of storms brewing off the coast.

But California still is not ready for another ARkStorm. Recent assessments concluded that such a storm could flood thousands of square miles, cause massive landslides, destroy extensive industrial and agricultural infrastructure, contaminate water supplies, kill thousands of people, and cost $1 trillion. That is three times the projected cost of an equally likely catastrophic earthquake.

Also different today is the climate. Human-caused climate change, not yet evident in the 1800s, is accelerating. Serious impacts are already apparent, including higher demands for water by humans, animals and plants because of increasing temperatures; rising sea levels from melting of land ice on Greenland and Antarctica; and more frequent and more extreme droughts and floods around the world.

Ironically, the floods hitting the West Coast now come on top of years of extraordinary drought. Eight of the past nine years in California have been extremely dry. In the Southwest, scientists are calling the past 22 years a “megadrought” — the worst in 1,200 years. When the rainy season began, sighs of relief could be heard from water managers and the public. Now that relief has turned to fear that the pendulum has swung hard to the other extreme.

We are not helpless in the face of extreme events. Far more must be done to increase our resilience — to strengthen the ability of nature and people to continue to thrive under these kinds of climate shocks, stresses and change. Most important is to cut the emissions of greenhouse gases worldwide, to slow and ultimately stop the climate changes that threaten us. But we must also work fast to address the effects we can no longer avoid.

Federal, state and local disaster planning must address more extreme events, including updating natural hazard maps to reflect new risks. Flood insurance and land-development programs must be overhauled to stop new construction in flood plains, to prevent rebuilding in risky areas after disasters, and to encourage gradual retreat over time from areas certain to flood. A top priority is revamping the National Flood Insurance Program that sets building and land-use standards for more than 20,000 communities across the country.

Water use — to grow food, run industries and supply domestic needs — must become much more efficient. And water supplies need to be expanded with innovative programs that capture more water during wet years and use it to recharge depleted groundwater, and by treating and reusing trillions of gallons of high-quality treated wastewater currently thrown away. Los Angeles’s plan to recycle and reuse 100 percent of its highly treated wastewater by 2035 is a good start.

It is important to engage the public about the growing risks of extreme floods and droughts and offer policies, information, and economic tools to reduce those risks. Our expectations have to change, from hubris in thinking that we can manage, manipulate and control nature, to understanding that we live within nature and must adapt.

A California reservoir update. Shasta, San Luis, Oroville (and others) are slowly adding water, but still FAR below normal (the blue curve). Folsom is spilling water as quickly as possible to restore flood storage space as water pours down the American River.


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