The deadly rainfall that has left many parts of Houston underwater has happened before and can happen again — not only in Texas but other cities that are unprepared. Houston has been known to flood even in moderately heavy rains — some of its roads are designed to collect large pools of water when the city’s drainage gets overwhelmed, which happens pretty often. And some parts of the city received an enormous amount of rain — more than 11 inches.
Houston is a pretty flat city in a subtropical climate just barely above sea level. Under those circumstances, realistically flooding may be unavoidable, even though the city is taking steps through its RebuildHouston initiative to improve the drainage system and address problem flooding areas.
But the fact remains that in some cities even just a few inches of rain can result in flooded basements and washed-out roads. Why? Because the way we have built cities makes them flood.
When we pave over absorbent dirt and grasses, rainwater runs off asphalt and concrete and often ends up overwhelming drainage systems and, in severe cases, flooding homes. The more impervious surfaces a city has, the more likely it is that it will suffer from urban flooding. Sprawling, heavily paved cities such as Houston can be especially vulnerable.
The Center for Neighborhood Technology analyzed National Weather Service data in 10 major cities across the United States, including Houston’s Harris County. We found that the residents in the county faced 145 flood warnings and alerts between 2007 and 2011 — that’s one every 12 days. Our research has also determined that flooding can happen in areas that are least expected — for example, our study of urban flooding in Cook County, Illinois, home to Chicago, analyzed data on insurance payouts for flood damage from 2007 to 2011 and found that 97% of Cook County’s ZIP codes experienced flooding, even if they were far from designated flood plains. Indeed some of the ZIP codes with the highest payouts had no flood plains in them at all.
Climate change will increase the frequency and intensity of rainstorms in much of the country. According to the federal U.S. Global Change Research Program, the type of heavy rainstorms that currently occur once every 20 years could happen at least twice as often in Southern states such as Texas if an aggressive emissions reduction program isn’t implemented. In other parts of the country, these storms could become up to seven times more frequent. Severe storms that now happen every 20 years could come every four years by 2100.
As the threat of climate change escalates, cities and regions must get serious about finding solutions. Our priority is to identify those solutions that bring quick relief to flood-prone homes, are affordable and effective: This requires a coordinated program of investment across private and public property, to help upgrade homes and streets to make them resilient to wet weather events.
The Center for Neighborhood Technology created its RainReady program as a municipal-scale initiative designed to bring communities together to find solutions to the problems of too much or too little water. We’ve brought together property owners, municipal officials and stormwater drainage experts to identify a community’s highest-priority drainage issues and determine the best set of strategies for minimizing property, yard and street flooding and the damage that comes with it.
Investments in natural and nature-based infrastructure to increase infiltration and collect rain where it falls, also known as green infrastructure, play a strong role in the RainReady program. Green infrastructure can, in some applications, be a more cost-effective approach than conventional stormwater infrastructure, and it can provide a whole set of benefits that “gray infrastructure” does not, including improved water and air quality, groundwater recharge, reduced stormwater runoff volume, additional wildlife habitat and recreational space and increased land values.
Coordinated landscaping, plumbing and building improvements for properties include backwater valves, downspout disconnection into dry wells and flood walls; runoff from alleys and parking lots can be captured through the installation of permeable pavement, trees and landscaped sidewalks; temporary water storage can be created from ponds, parks, urban forests and wetlands; and rain sensor networks can provide enhanced monitoring and flood alert systems for communities.
Building a resilient future needs to start now. Legislation such as the Urban Flooding Awareness Act, passed in Illinois last summer and currently being introduced at the federal level by Rep. Mike Quigley, D-Illinois, and Sen. Dick Durbin, D-Illinois, is an important first step in assessing the scope of the problem.
To avoid flooding devastation takes planning and foresight but also constant monitoring. The fact of the matter is, once a heavy rainstorm hits, there’s little a city can do to prevent flooding. Most preventative measures must be in place in preparation for these storms, because when the skies open up, all we can do is watch and learn where flooding is happening. Residents can play an important role in this monitoring by reporting pools of water hanging around long after the rains have gone to their municipalities.
While flooding may not be entirely preventable, that doesn’t mean it has to be catastrophic. There are lessons we can learn from Houston and steps we should be taking to prepare for and mitigate devastating impacts that the coming rainstorms can bring.
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