How to rebuild cities after hurricanes like Harvey

The aftermath of a disaster often focuses on getting back to normal, but do cities need to think harder about how to withstand the next one?

By Oliver Milman  /  The Guardian

Tue, Sep 12, 2017 - Page 9

US President Donald Trump visited a hurricane-stricken Houston and promised the “best ever” government response before pumping his fist from the steps of Air Force One as he departed.

Texas Governor Greg Abbott marveled that the state’s “resilient spirit is alive and well.”

The phrase “Houston Strong” has been daubed as graffiti on city underpasses and held aloft as placards at home baseball games.

There has been plenty of defiance, heart-rending loss and uplifting generosity in the wake of Hurricane Harvey, but one pressing topic has so far been largely overlooked: How will Houston rebuild in a better way should a storm like this ever visit again?

“When you talk about rebuilding a place like Houston, people’s first thoughts are: ‘I want it back the way it was,’” University of Maryland senior research engineer Sandra Knight said. “And unfortunately, that’s not the best thing to do. As a nation we aren’t planning forward enough. We are developing in places that aren’t sustainable. We need to start doing things differently.”

Abbott has said a “Texas-sized storm needs a Texas-sized response,” predicting that reconstruction after the heaviest rainfall event in recorded US history — about 94.6 trillion liters of water were dumped on a band of southeast Texas in just a few days — would top the US$120 billion required by New Orleans after Hurricane Katrina in 2005.

It might cost taxpayers more than US$180 billion, and it is not yet clear what lessons will be learned ahead of the rebuild.

The US places huge emphasis on flood recovery rather than avoidance, using the heft of the US Federal Emergency Management Agency to help those in need as well as administer a national insurance scheme that ostensibly places restrictions on what is built where, but in practice has repeatedly bailed out houses in flood-prone areas that are frequently inundated.

This emergency response is entirely appropriate in the immediate aftermath of a disaster, but at some point, a difficult conversation about whether a city needs to be refashioned as it recovers also needs to happen, New Orleans Chief Resilience Officer Jeff Hebert said.

“Houston had 51 inches [130cm] of rain and that would be disastrous for any city in the world — Mexico City, Bangkok, anywhere,” Hebert said. “It was unprecedented. The priority now is rescuing people and helping them.”

“The next phase of recovery is the appropriate time to talk about how to rebuild the city. Houston will have to think about retrofitting to accept more water and think about its development patterns. The city will have to think about how it manages storm water and its regulations,” he said.

Houston has taken a rather laissez-faire approach to city planning, with a lack of zoning allowing housing to spill out over a large expanse, often in areas next to bayous vulnerable to flooding.

The city is lacking in sponge-like parklands and is rich in concrete, which helps push water into unplanned streetscape swimming pools.

The flat terrain of Houston, along with its proximity to the hurricane-spawning Gulf of Mexico, are further vulnerabilities.

Climate change is playing a role — the warming atmosphere holds more moisture that falls in the sort of rain that swamped Houston. The seas are rising faster on the eastern seaboard of the US than almost anywhere else in the world, heightening the effects of storm surges from hurricanes.

Studies have shown that hurricanes are likely to get stronger, if not more frequent, threatening coastal areas that are growing in population size.

This challenge, plus the pummeling experienced during storms such as Katrina and Sandy, which hit New York and New Jersey in 2012, has forced several cities to think about more natural defenses to water, rather than simply rely upon levees and pumps.

“In Houston and elsewhere we’ve encroached upon our floodplains and we aren’t leaving any natural environment to slow the floodwaters,” Knight said. “We build dams and levees and people assume they are safe behind them, or downstream from them, but look at New Orleans — the levees failed.”

Knight said her initial training as a hydrological engineer focused on getting floodwater off your land as quickly as possible.

“But we’ve learned that’s not the best way to deal with floods,” she said. “We have a completely different landscape and climate now. They are complete game changers.”

In the 1950s, Dutch policymakers headed to New Orleans to learn how the city pumped excess water out into Lake Pontchartrain.

A year after Katrina hit, the Netherlands returned the favor by briefing officials from the Louisiana metropolis about the Dutch mantra of “living with the water.”

This principle involves huge fortifications in key areas against floodwater — New Orleans now has the largest flood barrier in the world — but also emphasizes the need for “green” infrastructure such as grass, woodland and wetlands to soak up water.

Innovations such as “green” rooftops, where plants absorb some rainwater before it is funneled to barrels rather than onto the street, and permeable pavements are also being embraced.

There are seven “rain gardens” in New Orleans — essentially parks where water pools and is absorbed — and the city is spending a further US$220 million on new green areas that will draw away water that would otherwise end up in the streets or in people’s homes.

Building codes have been tightened up to focus more heavily on flooding.

New Orleans is a different sort of city to Houston — it is older and has less available land to be eyed by developers — but Hebert said its approach can be replicated.

“After Katrina, we realized we had to live with water within the city,” he said. “We have hard infrastructure such as pumps, but also nature-based solutions because pumping can’t handle it all. We had to go back to what existed in the city in the 1930s and 1940s, before mass development took place.”

The idea that water must be given space to flow in times of flood is not new; the Yolo Bypass was constructed in the 1930s to relieve Sacramento from the severe floods that plagued it.

However, many US cities are still developing close to low-lying coastal and riverine areas with barely a nod to what floodplains actually do.

Some have leaned heavily on technology — Miami Beach, which has felt the effects of Hurricane Irma, has spent hundreds of millions of US dollars on raising its streets and developing a network of pumping stations. The low-lying city sits on a barrier island that already regularly floods on sunny days due to hide tides.

“Many cities have dams, levees and flood walls which are a fairly narrow and inflexible response to flooding,” WWF global freshwater lead scientist Jeff Opperman said. “There is growing appreciation in the US that we need to diversify, to set the levees back, use natural vegetation and allow the river room, but then there’s political decisions around development and that’s a less rational process.”

A 2015 study of six US cities found huge variations in response to extreme weather events fueled by climate change.

While New York City and Los Angeles were deemed as making progress, Tampa in Florida, which is also in Irma’s path, was found to be one of the least-prepared cities in the nation, with its main hospital — situated on an isolated low-lying peninsula — demonstrative of the lack of preparedness.

“There’s a big variation in how cities are preparing, some are doing almost nothing,” said Sabrina McCormick, an academic at George Washington University and lead author of the research. “Houston’s approach is similar to other cities in that it hasn’t looked into the future and taken the risks seriously. Unfortunately we are seeing the ramifications of that.”

McCormick said a lack of federal leadership is also a problem.

The Trump administration has struck down several regulations passed by former US president Barack Obama’s administration designed to reduce climate-driven risks.

Ten days before Harvey struck Houston, Trump tore up a rule that demands federally funded projects consider climate change and sea level rise before they are built.

“Ideally we’d have a national plan to help guide cities toward some basic level of planning to address these risks,” McCormick said. “If we don’t see that leadership, cities will have to look to other cities to figure out where to go next. We also need to mitigate our greenhouse gases to reduce the impact in the first place.”