Los Angeles County and Orange County have some of the largest areas of 500-year floodplains in Southern California. In the ARkStorm scenario those areas are at risk of deeper, deadlier flooding up to 10 feet.

And this is California’s most urban, population dense area. According to a 2013 analysis by the DWR, 338,100 structures and 48 percent of the population of Orange County, some 1.4 million people, are within in the 500-year floodplain in Orange County alone. Another 1.4 million people are within the 500-year floodplain in Los Angeles County.

But flood managers in those counties said that, though they had explored a 200-year level flood protection standard around 2005, they were content to follow the federal 100-year level standard and that funding was better served funding specific flood improvement projects, operating and maintaining current facilities and educating the public on the risks of living in a floodplain, regardless of protections.

“For them (DWR) to start upping it (flood protections) and say they’re going to 200 (year levels) I get concerned they’re creating a false expectation for the public that they don’t need to worry about flood protection,” said Los Angeles County Public Works Director Mark Pestrella.

“The fact of the matter remains that there is still is a floodplain, regardless of that protection. If you’re going forward in new areas, and you choose to do a 200-year-level of flood protection, you have to be able to tell a property owner you can buy a house here, here’s what your risk is going to be. But you still have risk. That risk never goes away. It’s always there.”

Pestrella said that the system in Los Angeles provides a range of individual flood protection measures above and below the 200-year standard, but that overall, the county’s system meets 100-year level standards.

Orange County, on the other hand, is still struggling to meet the 100-year federal flood protection standard.

In 2013, a joint report from the DWR and the USACE — which helps manages the maintenance of many of the levees and dams in the highly populated floodplains in Los Angeles and Orange Counties — found something troubling.

“Orange County estimates that it would take 90 years at current funding levels for the county to fund the approximately $1.5 billion in projects necessary to bring its facilities to a 100-year (1 percent) flood recurrence probability design level,” the report said.

The Orange County Flood Control District (OCFCD), which manages flood protections in the county, said that the deficiencies identified in the report were still accurate and that the district was using the information from the report to maintain and improve specific projects within its system.

“The County of Orange is dedicated to improving our flood control system as funding allows,” an OCFCD spokesperson said.

In one specific project, a federal and locally funded study completed in 1975 found that the flood control system for the Santa Ana River, whose floodplain also stretches into San Bernardino and Riverside counties, only had 70-year levels of flood protection.

So, since 1988, the USACE, in tandem with the three local water authorities, has spent $1.3 billion on refortifying the areas flood protections in the so-called Santa Ana River project. The three-phase project even included building a new dam (Seven Oaks Dam), and once completed, will provide 190-year level flood protection for Orange County and other flood prone areas along the Santa Ana River, a massive improvement compared to 40 years ago.

The work, nearly 30 years later, is still not complete. OCFD said that the total estimated cost of the Santa Ana is expected at around $2.3 billion and work, if federal funding comes through, should be completed by 2024.

Federal funding and maintenance was a sticking point for both both Orange County and Los Angeles County. Flood control authorities there said the federal government hadn’t funded specific projects or necessary maintenance on the facilities that the federal government is supposed to maintain.

Pestrella said, for instance, that Los Angeles’ greatest need is investment in maintaining the reservoirs that hold floodwaters back from the area, which have become choked with sediment, reducing their capacity to store water. Funding for that sort of maintenance is often not covered in the water bonds, Pestrella said.

“For us, it’s investing in maintenance and operation rehabilitation, which the federal government has done a really poor job of,” Pestrella said. “Most of the problems you see are the federal agencies not maintaining the facilities properly. Not that they (the facilities) aren’t big enough, but that they’re not maintained properly over time.”

Because Mierzwa said that the Central Valley had a more immediate need to improve some of the worst infrastructure in the state, most of the funding from the water bonds has gone there, leaving only relatively small amounts for Southern California. For instance, an OCFCD spokesman said that the district had received grants ranging from $5 million to $15 million in the last 10 years, far short of what’s needed to fill the $1.5 billion gap in funding needed to reach the 100-year standard countywide.

All told, Mierzwa said that the state needs $80 billion over the next 50 years to continue improving flood protections statewide. And $59 billion of that $80 billion is needed to tackle lingering issues in the rest of the state, outside the Central Valley, in places like San Francisco and Orange and Los Angeles Counties.

Even if all of California’s urban areas met the 200-year-level standard being pursued in the Central Valley, the level of protection likely isn’t enough. The 200-year urban level protection, as ambitious as it is, won’t realistically protect against the 500-year-plus level floods of California’s ARkStorm.

“The 200-year standard is just like the 100-year standard, it’s a number that sounds good,” said Mierzwa. “It doesn’t work, statistically, that 200-year protection cuts risk of flooding down to 1-in-8, it’s more around a 1-in-6 chance over 30 years when you get to a 200-year level flood protection.”

So, if 200-year level protections won’t protect against an ARkStorm, against California’s realistic, climate change-fueled megaflood, why not move toward a higher standard? Why not 500-year levels of protection or beyond?

For Pestrella, investing in flood protections to 200 years and beyond isn’t a cost effective solution to combating climate change and its “incredibly improbable” potential floods.

“Although, yes, we’re seeing things like Houston (Hurricane Harvey’s floods) happen, Houston is an incredibly improbable event that happened. Could you build facilities large enough to deal with that? Probably not,” said Pestrella. “So those folks that live in the 500-year floodplain would just need to be educated that occasionally, in a very improbable event, you’re going to see water in the home.”

Mierzwa, on the other hand, seems to think that the Central Valley and other parts of the state could be re-engineered to protect for the potential 500-year floods an ARkStorm could produce if the state had the time.

“The 200-year level was a stepping stone because we knew it would be cost prohibitive to get to what we’d prefer — which is an even greater level of protection — and we haven’t specified what the number is on that,” said Mierzwa.

There are no current pieces of infrastructure or plans with 500-year levels of protection just yet, Mierzwa said. But he said that, while there’s no official price tag on 500-year level of protection, state officials have been sniffing around a higher level of protection since all of this began in 2005.

“Is it (500-year-level of protection) cost prohibitive? No. But is it (the 500-year standard) something that’s reasonable to accomplish in the next 30 years? Probably not.”

The cost of 500-year level protection in just the Central Valley, Mierzwa said, likely wouldn’t be double that of the current $21 billion price tag for the area to reach 200-year levels.

Mierza said the current 30-year planning horizon in the Central Valley is essentially the limit to public planning. Beyond 30 years, he said, you lose political support for funding through things like bonds because it becomes harder, with inflation and costs, to calculate your return on investment.

“When you start doing the present worth of all those future benefits anything after 30 years becomes trivial in the present value of money out there, said Mierzwa. “From a fiscal standpoint the way Congress, state and even local municipalities look at it, you don’t look at investments after 30 years. It’s better to have that money in hand to spend on something now.”

And California would have to dramatically re-engineer itself to reach a 500-year level of protection and beyond, something that would take decades to accomplish, well beyond 2050 and that 30 year planning threshold.

According to Mierzwa, because of the exponentially higher volume of water involved in a 500-year level flood, the current flood protection system would have to be rethought, with bypasses/channels upstream from major urban areas expanded to allow more water to pass through and then be funneled into new, larger designated floodplains away from people. The current system simply can’t handle that much water.

“If we had 20 inches in two weeks a reservoir alone is not going to do it. There’s no way that we could have a channelized levee system convey those flood flows,” said Mierzwa. We’re absolutely going to require to have big massive bypasses and floodplains that can actually take some of that water on.”

Climate change is the cog turning independent of the state’s efforts through 2050. Global temperatures continue to rise, providing more moisture-laden fuel for atmospheric rivers. And the new, worst case scenario normal for atmospheric rivers, the one that brings more intense ARs, begins in 2070 in Ashley Payne’s research.

California still needs at least $80 billion, and at least three decades, just to catch the flood protection system up to today’s standards. After 2050, it needs even more money and even more time to catch the flood protection system up to climate change’s worst projected flood.