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Ageing sewers and climate change behind flash floods in Washington

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Cristina Novo
Technical Editor at Smart Water Magazine.

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  • Ageing sewers and climate change behind flash floods in Washington
    Flooding in January 2009 closed a section of Interstate 5 south of Seattle.Washington State Dept. of Transportation

Last Monday a month’s worth of rain fell on Washington DC flooding streets, basements and any low-laying areas, reported The New York Times.

Washington’s weather station at Reagan International Airport recorded 3.44 inches on July 8th, an amount that overwhelmed the capital city’s storm sewer system. Most it was built almost one century ago (the average water main is 79 years old), for a smaller population, a smaller paved surface, and not so much water. The flash floods reveal the vulnerability of cities with ageing sewer systems against climate change.

Updates to 20th century water infrastructure come at a huge cost, not just in Washington but across the United States. On top of that, many cities lag in general system maintenance. Last May a needs assessment by the Water Environment Federation, a non-profit water industry association, revealed an estimated $7.5 billion annual funding gap in the U.S. stormwater sector.

Although no single weather event can be directly linked to climate change, extreme events like Monday’s storm do follow a general pattern: warmer air can hold more moisture, leading to heavier rainfall episodes.

D.C. Water, Washington’s utility, has cautioned about the enormous challenge of keeping up with routine maintenance while taking into account evolving rainfall patterns and the city’s growth. Funding is a key issue: the utility has introduced a storm-water surcharge, but increasing the rates too much may strain the budgets of those residents with limited incomes.

Affordability is thus a genuine concern, and so planning for future climate effects is not always within reach. Authorities and regulators across the States are hesitant to approve rate increases to upgrade systems and make them climate ready.

In fact, cities already find it difficult to meet current upgrade needs because citizens cannot see the results as easily as those of other city investments, as sewers are ‘out of sight, out of mind’, thinks Erik D. Olson, from the Natural Resources Defense Council. Then again, recent events like Monday’s storm and its consequences may bring this issue to the forefront of municipal agendas.

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