Tempting Fate: Are We Next?

In cities across the nation, rivers, streams, lakes, creeks and seas have made their sinister mark, inflicting damage and heartache when they flood.

There is, however, no major city in America more at risk of a catastrophic New Orleans-style flood than Sacramento.

That is the firm and unnerving conclusion drawn from a Bee survey of the 30 largest metropolitan areas in the nation, conducted over the past month. Compared with other big cities, Sacramento is marked by a potentially deadly combination of geographic, hydrological and demographic factors unmatched anywhere in the United States.

Take a look at the collection of strikes against us:

• We sit at the confluence of two major rivers, the Sacramento and the American.

• They drain vast watersheds that begin high in the mountains, meaning a major flood would come with staggering volumes and ferocious velocities.

• Huge sections of Sacramento - including miles of neighborhoods, the downtown commercial center and the state Capitol - rely on levees to keep from going under in times of high water.

• Unlike other cities that sit on high ground or bluffs above rivers, much of flood-prone Sacramento sits lower than the levees and the rivers at flood stage. That means places such as Natomas, downtown, east Sacramento, Rosemont, North Sacramento, Oak Park, Curtis Park, Land Park, River Park, Greenhaven, the Pocket, south Sacramento and assorted neighborhoods along the north and south sides of the American River would fill up like giant soup bowls during a disaster-level flood.

• Sacramento's levees offer less protection than those in many other cities. Officials worry they could fail or overtop if a large late winter or early spring storm system brought more water than they were designed to handle. Warm "Pineapple Express" systems are especially feared, because they can sidle up against the mountains, rain for days, and cause too much snow to melt at once and barrel down river corridors.

• Recently, a new and insidious worry has emerged: Engineers discovered after the floods of 1997 that seepage is occurring deep beneath Sacramento area levees that could cause internal erosion and unforeseen failures.

• Beyond the levees is another concern: Folsom Dam, which holds back the American River to the east of the downtown core, is ranked No. 1 on the federal Bureau of Reclamation's safety priority list. With nearly a million people living downstream, no other dam in America has greater need of additional protection against a monster storm, according to the bureau.

• Finally, unlike other cities, where flooding may be severe but tends to occur on a localized scale, a major flood in Sacramento would spread for miles and run as deep as rooflines in some places. According to the Sacramento Area Flood Control Agency, more than 300,000 people and 140,000 structures are in the direct path of a serious flood in Sacramento.

In the eyes of the nation's top flood experts, only one other big city could rival Sacramento for the top catastrophe-prone title.

And it has been largely destroyed.

"When people talk about the mega-disaster, they talk about New Orleans and they talk about Sacramento," said Doug Plasencia, an Arizona engineer and former chairman of the Association of State Floodplain Managers.

Darryl W. Davis, director of the hydrologic engineering center for the U.S. Army Corps of Engineers in Davis, was equally blunt.

"There is no question in my mind that Sacramento is at the highest flood risk in the nation," he said.

Sacramento flood officials got a glimpse of the grim local picture about 15 years ago, when they compared the capital's flood protection with at least seven other cities with known flooding risks. Though limited, the review caused eyes to pop: Cities such as Tacoma, St. Louis and Kansas City had 500-year protection from flooding, while New Orleans and Omaha were in the 250-year range. Sacramento, in contrast, had less than 100-year protection at the time - a figure that has improved only slightly since.

In flood control circles, such numbers are used to describe the size of storm events. Many people mistakenly believe a 100-year event won't happen for a hundred years.

But the situation is much more risky.

A 100-year event is a storm that has a 1 in 100 chance of occurring in any given year. Such a flood would be a whopper; the flood that hit Sacramento in 1986 did not reach that level, yet it was devastating, with hundreds of homes in Rio Linda, Roseville and Strawberry Manor submerged. One-hundred-year protection means the system of levees and dams is designed to withstand a 100-year event; anything beyond that is a question mark.

A 200-or 500-year event would be much larger and rarer, with the corresponding protection more substantial as well.

Storm surges, flash floods, deep waters

In early October, The Bee set out to learn whether the "most at-risk city" distinction would hold up if every major metropolis in America were taken into account. During the past several weeks, the newspaper contacted flood control and emergency preparedness experts in the nation's 30 largest metropolitan areas, asking them to describe their local flood worries.

The responses came with vivid descriptions of powerful waterways coursing through urban communities.

The city of Pittsburgh has three great rivers; the Allegheny and the Monongahela meet to form the Ohio. St. Louis was founded near where the Missouri River meets the Mississippi. Portland has the Willamette and Columbia rivers flowing through populated areas. In Dallas, the Trinity River runs straight through downtown.

In city after city, civic leaders spoke of significant flooding concerns.

When hurricanes or coastal storms strike cities such as New York, Miami or Baltimore, giant storm surges can wash ashore, leaving devastation behind. The Denver area, particularly Boulder, faces brutal flash flooding out of the Rockies. During the massive Midwest flooding of 1993, Kansas City held its breath while levees along the Kansas and Missouri Rivers (which meet in the heart of the city) were filled nearly to overflowing and numerous small towns along the Missisippi were inundated.

Harris County, Texas, home to low-lying Houston, has the distinction of having more declared disasters than any other county in the nation. The bulk are due to flooding from warm Gulf of Mexico storms that park in the vicinity and dump monumental amounts of rain.

Yet, when the Harris County coordinator of emergency management finished recounting to The Bee his experiences with relentless rains, rising streams, 12-foot flood depths and numerous drownings, he concluded by saying he would rather live in Houston than Sacramento.

"Our floods may be more frequent, but our water comes up slowly," Harris County's Frank Gutierrez said. "Where you are, you're talking about a sudden wall of water coming at you. It's a far different thing."

Even San Antonio, dubbed "Flash Flood Alley" by the National Weather Service, is no match for the widespread risk facing Sacramento, said Mark Lenz, a senior service hydrologist with the Weather Service for that area.

The difference is this: San Antonio has chosen to provide its downtown commercial areas with 300-year protection via a dam upstream on the San Antonio River, plus two concrete-lined flood control tunnels built under the same river to carry excess water in flood times. Many other residential areas of San Antonio still face harsh and frequent flash flooding from other streams, sometimes in the space of an hour. But the floods, while numerous, occur in localized areas and the waters wash away as quickly as they come.

Most significantly, San Antonio, like many communities that live with flooding, is familiar with how bad things can get.

In Sacramento, the great flood that may lie in our future is unimaginable.

"I manage one of the most dangerous watersheds in the upper Midwest," said Steve Oltmans, general manager for the Papio-Missouri River Natural Resources District, which includes Omaha, the nation's 60th largest metropolitan area.

"But you're in a whole different league out there," Oltmans said. "You've got major flooding issues. And it's the capital city of the state. It just amazes me."

Tall levees, low lands

The Sacramento metropolitan area, with nearly 2 million people, is the 26th largest population center in the country, based on 2003 adjusted U.S. census figures. No. 1 is New York City with 18.6 million people, followed by Los Angeles, Chicago, Philadelphia and Dallas. No. 30 in the Bee's study group was the San Jose/Santa Clara area. In between came such cities as Detroit, Seattle, Minneapolis, Cleveland, San Antonio and Orlando, Fla.

Among cities, Sacramento has geographic circumstances that set it apart.

Its rivers became more shallow because of debris and sediment from hydraulic mining in the Gold Rush era (cannons blasting water into the mountainsides to free up the gold), said Ricardo Pineda, chief of the floodplain management branch of the state Department of Water Resources. The shallow rivers flooded often, depositing debris that made for higher riverbanks.

In later years, farmers and laborers topped the banks with rocks, dirt, sand, whatever they could find, to hold back the rivers. The result: towering levees that overshadow low-lying lands, a topographical feature that has taken on a legendary mystique among those tuned in to such things.

"I remember when I came to live in Sacramento in about 1980," said Dennis Mileti, director emeritus for the Natural Hazard Center at the University of Colorado at Boulder. "I was amazed when someone showed me the rivers, and I had to look up at them."

During the dry season, the levees are friendly companions on the landscape. But when the heavy rains of winter come, they hold rivers that end up running higher than the neighborhoods nearby.

"One of the things that has always been spectacular about Sacramento," said Joe Countryman, president of MBK Engineers, a Sacramento firm, "is how you could go from nothing to huge water flows... from sunshine and bluebirds to maximum flows stressing the entire flood system."

The Sacramento River, for example, can go from flows of 15,000 cubic feet per second during the calm days of early autumn, to a raging half-million during a high rain event, such as those that happened in 1986 and 1997.

"It could happen in three to five days here," Countryman said. "It would take three to five weeks on the Mississippi River to do that. There's much less time for evacuation."

Flood walls, dams and tunnels

During heavy rains, most cities in the country endure localized flooding from overextended storm drainage systems. The events can be miserable.

But many of those with major rivers don't worry about their big waterways flooding. In some places, such as St. Louis, Philadelphia, Detroit, Pittsburgh and Minneapolis/St. Paul, this is because development has been situated on higher banks or hills overlooking the rivers. In others, such as Washington, D.C., and New York City, the prominent rivers (in these cases the Hudson and Potomac) drain into ocean bays with plenty of space for extra water.

In still others, the towns have taken major steps to protect themselves with concrete flood walls, dams, detention reservoirs, setback levees and even underground flood relief channels.

Take Dallas. To protect its downtown area from the Trinity River, Dallas has built levees set back about 1,000 feet from each side of the river to create a wider channel in times of high water. Dallas has 10,000 structures in flood-prone areas, but its 23 miles of earthen levees are built to a 300-year protection level, much higher than Sacramento's.

St. Louis has even more protection. Its downtown sits on high ground that wouldn't flood. Other parts of St. Louis are protected by a concrete floodwall with steel gates that can be installed when the Mississippi's waters get high. It all adds up to about 500-year protection, said Dave Busse, chief of the hydraulics branch for the St. Louis District Army Corps of Engineers.

Portland, Ore., which also has 500-year protection for most developed areas, features a similar concrete seawall with installable steel panels for times when the Willamette River threatens. Boston has created an 8,000-acre wetlands area to absorb overflow from the Charles River.

Austin, the capital of Texas and the nation's 38th largest metro area, has drawn a significant line along its rivers and streams. After 13 people died in a 1981 flood, the city said no more building in the 100-year floodplain.

"When people die it is not a good thing," said George Oswald, manager of the watershed engineering division for the city of Austin. "We are keeping development out of harm's way. It's not easy because the developers are always hounding us."

Gerald Galloway is a professor of water resources management at the University of Maryland and one of the nation's pre-eminent flooding authorities. He was asked by the White House to prepare a report on the nation's overall flood situation after the Midwest floods of 1993, and concluded that citizens in large population centers should have at least 500-year protection. In a recent interview, he explained the threshold as necessary "because the consequences of failure for a major population center are enormous."

In a community such as Sacramento, where many live and work behind levees, people should be concerned about their situation, he said.

"What makes yours so unique," Galloway said, "is that everything is OK up to a point and then it all happens. You think you are protected, but if a levee is exceeded, the damage goes out of sight."

According to Stein Buer, executive director of the Sacramento Area Flood Control Agency, engineers have strengthened many local levees to bring them to the 100-year protection level, and expect to reach that threshold soon in Meadowview and the Pocket. They also are struggling to tackle the underground seepage discovered in recent years.

Officials wish they could do more, Buer said, but state and local budgets do not allow for it.

Mother of all floods

Jeff McCracken, spokesman for the federal Bureau of Reclamation, said the bureau could achieve at least 200-year protection on the American River by building side spillways on Folsom Dam. The dam's existing outlets are too small, raising the chances operators could not draw down the reservoir sufficiently before a huge storm hit. (During the floods of 1986, one more inch of rainfall might have caused the dam to overtop.) The new spillways would allow more water out more quickly, and are being studied in Congress.

But no amount of work on the dam could hold back the "Probable Maximum Flood," a term for the worst possible storm event that the area could reasonably expect to occur. A 2001 risk analysis by the bureau found such a storm would create three times as much water as a 100-year event, flowing at three times the speed. It would happen in a five-day period and create an uncontrollable flood that would overtop the concrete face of the dam, crumble its earthen sides and quickly engulf communities from Carmichael and Gold River to downtown and Elk Grove.

There is a one in 7,000 chance of such a storm occurring in any given year - a long shot but still possible.

It is the reason, along with the large population at risk, that Folsom Dam now sits at the top of the bureau's dam safety priority list, McCracken said. The new spillway project would not stop the giant flood, but it would preserve the main dam in such a disaster, along with providing the immediate benefit of 200-year protection on the American.

McCracken emphasized that on a day-to-day basis, Folsom Dam is a safe structure and does its job well.

In the meantime, local political and flood leaders recommend that Sacramentans carefully assess their personal situations and, depending on where they live, carry flood insurance, prepare a stash of emergency provisions and have a plan for evacuating to high ground should a flood occur.

FLOOD STRUGGLES

Here's a look at some other large cities across the United States that have had to cope with the risk of major flooding:

DALLAS

Flood threat: The Trinity River, the largest and longest river in Texas, runs through downtown Dallas on its way to the Gulf of Mexico. It usually has low waters, but when the rains hit, it can fill fast.
What's been done: Dallas has 23 miles of earthen levees offering 300-year protection. Downtown is protected by a 10-mile floodway where levees were moved out 1,000 feet on either side of the Trinity to create a wider channel for heavy flows.

PITTSBURGH

Flood threat: Pittsburgh has three great rivers meeting in its midst, the Allegheny, the Monongahela and the Ohio. Until recently, it even had a civic jewel named in their honor: Three Rivers Stadium.
What's been done: Pittsburgh beat the flooding odds years ago by raising much of the ground along the rivers before developing. The steel industry contributed with slag, a byproduct used for infill. It would take a 500-year event before extensive flooding could occur.

SAN ANTONIO

Flood threat: Dubbed "Flash Flood Alley," the San Antonio area frequently gets hit with sudden and brutal floods from gulf storms of startling intensity.
What's been done: San Antonio has numerous neighborhoods at serious risk, but has provided its downtown with stepped-up protection via the Olmos Dam, which can hold back a 300-year storm event on the San Antonio River. In addition, seven years ago, the city completed two concrete-lined flood control tunnels that run under the river and carry away excess water when the river threatens.

BOSTON

Flood threat: The Charles River runs through Boston and once posed a serious flood risk.
What's been done: A series of dams and water basins now controls flows along the river. In addition, in 1974, the Army Corps of Engineers bought up land and set aside an 8,000-acre wetland area to absorb overflows. Besides flood protection, the Charles River Natural Valley Storage Area is used by the public for recreation and wildlife viewing.

ST. LOUIS

Flood threat: St. Louis is built at the confluence of two powerful waterways, the Missouri and the Mississippi. Most of the central business district is on high ground, but vast lower lying tracts once were vulnerable.
What's been done: Today, most areas at risk have 500-year protection, thanks to a concrete floodwall built along the Mississippi about 30 years ago. It has openings for public access that can be closed with steel gates when the river gets too high.

AUSTIN

Flood threat: Austin has 40 creeks crisscrossing the urban area, intense rains from the gulf and frequent flash floods.
What's been done: In the mid-1970s, Austin began adding dams, levees and detention ponds. And still people died in floods. In 1983, the city took the dramatic step of extending its no-build zone (which covered only the most high-risk areas in the 25-year floodplain) to include the much broader 100-year floodplain. Recently, concrete flood walls were built along some waterways.