Climate Central - Alyson Kenward | Nicole Zenes | James Bronzan | Jennifer Brady | Kasturi Shah
Record rainstorms across the U.S. in the past year have continued to
make national news, causing billions of dollars of flood damage and
killing dozens. But what has barely made headlines are that these floods
often cause massive overflows of untreated sewage into streams, rivers,
bays, canals, and even streets and homes. See the full report.
Climate Central has investigated the extent of these sewage
overflows. In most cases, we found reports that millions of gallons of
untreated sewage were released into streets and waterways. These
overflows can have devastating consequences for public health and the
environment: they can trigger dangerous outbreaks of waterborne diseases
and are often linked to fish kills. And when sewage overflows into
homes and businesses, expensive remediation and decontamination is
needed to make them safe again.
Worse was the discovery that the true extent of sewage overflow is often undocumented and largely unknown.
From the 70 sewage overflows we identified that had occurred in the
past 20 months, overflows of more than one billion gallons combined were
reported, triggering health warnings in dozens of cities. Local
officials confirmed that these reported volumes are likely
underestimating the true extent of overflows; during these flooding
emergencies, there is typically no reliable way to determine how much
untreated sewage gets into the waterways.
With a backdrop of antiquated and overpopulated sewer systems, the
increase in rain and heavy downpours in recent decades — one of the
ongoing impacts of climate change — continues to trigger overflows that
affect millions of Americans every year.
While many cities are working toward upgrading their sewer systems,
they can’t eliminate their sewage overflow risks entirely. Climate
models project that both overall precipitation, and the amount of rain
falling in heavy downpours, will continue to increase this century with
continued climate change, which could cause even more overflows.
According to the National Oceanic and Atmospheric Administration (NOAA),
the epic rains in Louisiana in August 2016 that flooded 60,000 homes
and killed 13, were made nearly twice as likely
due to carbon pollution in the atmosphere. Climate Central’s analysis
of more than 3,000 rain gauges nationwide shows that heavy downpours are
happening more frequently than they did in the 1950s. We found that all
but two of the Lower 48 states have seen an increase in the number of
heavy downpours happening each year, on average, compared to the 1950s,
and 28 states have seen at least a 25 percent increase in these heaviest
events. With downpours projected to be even more frequent and intense
as the world continues to warm, we can expect more of these costly and
dangerous overflows for many years to come.
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