In this stretch of the Mid-Atlantic, waters are rising at among the fastest rates in the world — a U.S. government station in Myrtle Beach has recorded nearly 10 inches of sea level rise since the late 1950s, and the trend has accelerated in recent years. Add to thatmore intense hurricanes, torrential rainstorms, feverish development that alters water flow and other factors, and more and more communities like this one find themselves in the path of floodwaters.
Already, according to one seminal study that examined voluntary buyouts between 1989 and 2017, the government has paid for more than 43,000 buyouts of flood-prone properties across 49 states and more than 1,100 counties.
It wasn’t long after Henry David Inglis arrived on the island of Jersey, just northwest of France, that he heard the old story. Locals eagerly told the 19th-century Scottish travel writer how, in a bygone age, their island was much more substantial, and that folks used to walk to the French coast. The only hurdle to their journey was a river—one easily crossed using a short bridge.
“Pah!” Inglis presumably scoffed as he looked out across 22 kilometers of shimmering blue sea—because he went on to write in his 1832 book about the region that this was “an assertion too ridiculous to merit examination.” Another writer, Jean Poingdestre, around 150 years earlier, had been similarly unmoved by the tale. No one could have trod from Jersey to Normandy, he withered, “vnlesse it were before the Flood,” referring to the Old Testament cataclysm.
Rather than being a ridiculous claim not worthy of examination, perhaps the old story was true—a whisper from ancestors who really did walk through now-vanished lands. A whisper that has echoed across millennia.
That’s exactly what geologist Patrick Nunn and historian Margaret Cook at the University of the Sunshine Coast in Australia have proposed in a recent paper.
Dallas was hit with nearly 15 inches of rain that turned roads into rivers and poured into homes starting Aug. 21, 2022. Neighborhoods in Jackson, Mississippi, were inundated a few days later as the Pearl River rose and a water treatment plant breakdown left the city without clean drinking water. In late July, extreme storms struck the mountains of eastern Kentucky, sending rivers sweeping through valley towns and triggering mudslides that killed more than three dozen people.
Floods are complex events, and they are about more than just heavy rain. Each community has its own unique geography and climate that can exacerbate flooding, so preparing to deal with future floods has to be tailored to the community.
I work with a center at the University of Michigan that helps communities turn climate knowledge into projects that can reduce the harm of future climate disasters. The recent floods provide case studies that can help cities everywhere manage the increasing risk.
Flood risks are rising
The first thing the recent floods tell us is that the climate is changing.
In the past, it might have made sense to consider a flood a rare and random event – communities could just build back. But the statistical distribution of weather events and natural disasters is shifting.
What might have been a 1-in-500-year event may become a 1-in-100-year event, on the way to becoming a 1-in-50-year event. Hurricane Harvey in 2017 delivered Houston’s third 500-year flood in the span of three years. Ellicott City, Maryland saw catastrophic floods in 2016 and 2018, and the town flooded again in June 2022.
Basic physics points to the rising risks ahead: Global greenhouse gas emissions are increasing global average temperatures. Warming leads to increasing precipitation and more intense downpours, and this increases flood potential.
Communities aren’t prepared
Recent floods are revealing vulnerabilities in how communities are designed and managed.
Pavement is a major contributor to urban flooding, because water cannot be absorbed and it runs off quickly. Similarly, after a forest fire or extended drought, water runs off of soil rather than soaking in. This can overwhelm drainage systems and pile up debris that can clog pipes and culverts.
Failures in maintaining infrastructure, such as levees and storm drains, are a common contributor to flooding.
If the infrastructure is well designed and maintained, flood damage can be greatly reduced. However, increasingly, researchers have found that the engineering specifications for drainage pipes and other infrastructure are no longer adequate for the increasing severity of storms and amounts of precipitation. This can lead to roads being washed out and communities being cut off.
By addressing these issues now, communities can anticipate and avoid damage rather than only reacting when it’s too late.
Four lessons from case studies
The many effects associated with flooding show why a holistic approach to planning for climate change is necessary, and what communities can learn from one another. For example, case studies show that:
It is difficult for an individual or a community to take on even the technical aspects of flood preparation alone – there is too much interconnectedness. Protective measures like levees or channels might protect one neighborhood but worsen the flood risk downstream. Planners should identify the appropriate scale, such as the entire drainage basin of a creek or river, and form important relationships early in the planning process.
In the communities that my colleagues and I have worked with through the Great Lakes Integrated Sciences and Assessment center, we have found an increasing awareness of floods and, more generally, the challenges of a warming climate.
Many communities have some capacity to deal with weather-related hazards, but they realize that past practices will not be adequate in the future.
We have found that by focusing on vulnerabilities, discussions about future climate risk become more real. Communities start to recognize the interconnectedness of zoning, storm drains and parks, for example, and the value of clearing of debris from stream beds. They also see the importance of engaging regional stakeholders to avoid fragmented and ineffective adaptation responses.
We use scenario planning to help officials examine several plausible climate futures as they develop strategies to deal with specific management challenges. Examining case studies and past floods provides a way to consider future flooding events from an experience base of known community vulnerabilities.
In most exercises I have participated in, local officials’ instinct is to protect property and persist without changing where people live. However, in many cases, that might only buy time before people will have little option but to move. Scenario planning can bring focus to these difficult choices and help individuals and communities gain control over the effects of climate change.
This article was updated Aug. 26, 2022, with flooding in Mississippi.
The Federal Emergency Management Agency has removed publicly available records from its website that showed hundreds of thousands of people had dropped their federal flood insurance policies in recent months.
FEMA pulled the records after E&E News cited the data in an Aug. 17 news article that revealed more than 425,000 people had discontinued their policies with the agency’s National Flood Insurance Program since October (Climatewire, Aug. 17).
The agency said it removed the records to correct inaccuracies and it did not know when the data would be restored. A note on FEMA’s website says the reports “should be available within the coming weeks.”
As of the date of publication, 35 states have enacted some form of legal or regulatory mechanism requiring property sellers to disclose factors related to flood risk about their property. This guide identifies states with the strongest flood risk disclosure requirements and provides a selection of their laws and disclosure forms as models for use in introducing or strengthening a state’s real estate disclosure requirements.
The McKinney fire began on July 29 and has exploded to more than 60,000 acres, killing four people and becoming California’s largest fire so far this year. According to local tribal leaders, the fire has also led to the mass fish kill in the Klamath River, which runs for more than 250 miles from southern Oregon, through Northern California and out to the Pacific Ocean.
Extreme floods are devastating Pakistan, caused by a combination of heavy monsoon rains and melting glaciers. While Pakistan is no stranger to deadly floods, this event is especially shocking with more than 1,100 people dead so far and many millions more affected.
This Northern Hemisphere summer has seen extreme weather event after extreme weather event, from record-breaking drought in Western Europe, the United States and China, to flooding in Japan and South Korea.
This begs the question of the extent climate change is to blame. And, if so, is this what we should expect from now on?
A summer of extremes
The flooding in Pakistan is the latest in a sequence of exceptional disasters in the Northern Hemisphere.
Western Europe and central and eastern China have experienced record-breaking heatwaves and droughts leading to water restrictions. These heatwaves and droughts have also caused crop shortages, which are adding to the rising costs of food around the world.
While it’s true that several of this summer’s extreme events have been exceptional, we normally see more high-impact extreme weather events in Northern Hemisphere summer than any other time. This is because extreme heat, very heavy downpours, and drought are more likely at the warmest time of year.
Two-thirds of the planet’s land and more than 85% of the world’s population are in the Northern Hemisphere. This means there are more people to be affected by extreme weather than in the Southern Hemisphere, making the Northern Hemisphere summer the prime time for disasters to have severe impacts.
Additionally, extreme weather events can occur at the same time over different places, because of large-scale atmospheric waves called “Rossby waves”, which are a naturally occurring phenomenon, like La Niña and El Niño.
Back in 2010, western Russia experienced severe heat and wildfires while Pakistan had some of their worst floods to date. These events were connected by a Rossby wave causing a high pressure pattern to get stuck over western Russia and low pressure to persist over Pakistan.
Rossby waves can also result in heatwaves occurring at the same time, thousands of kilometres apart. Earlier this Northern Hemisphere summer, we saw simultaneous heatwaves strike the western US, western Europe and China.
Rossby waves may well have contributed to simultaneous disasters this summer, but it’s too soon to say for sure.
Climate change and the never-ending extremes
With so many extreme weather events causing mass deaths and large economic and environmental problems, it’s worth considering whether climate change may be making these events worse.
Human-caused climate change has warmed the planet by about 1.2℃ to date and this has caused some types of extreme weather to become more frequent and more intense, particularly extreme heatwaves and record-high temperatures.
Every heatwave in today’s climate has the fingerprint of climate change resulting from our greenhouse gas emissions. Indeed, rapid analyses have already demonstrated that the human effect on the climate greatly increased the likelihood of the extreme heat in India and Pakistan in May, and the record high UK temperatures in July.
Research also shows climate change is increasing the occurrence of simultaneous heatwaves in the Northern Hemisphere, mainly due to long-term warming.
It’s less clear whether the Rossby wave pattern that causes simultaneous heatwaves in different places is becoming more frequent.
Climate change is also shifting rainfall patterns resulting in worsening drought in some areas, such as in much of Western Europe.
And severe downpours and extreme short-duration heavy rain, such as that seen in Seoul and Dallas in recent weeks, are being intensified by climate change. This is because global warming results in the air being able to hold more moisture – for every 1℃ of warming, the atmosphere can hold 7% more moisture.
Indeed, the heavy rains in Pakistan follow an observed trend towards increasing extreme daily rainfall totals. This area of the world is projected to see a continued intensification of daily and multi-day extreme rain events over summer, as the planet warms.
Worse extremes to come
We can expect more extreme weather events in the coming years as global greenhouse gas emissions continue at near-record rates.
Some heat extremes in recent years have been far beyond what we thought would happen after just over 1℃ of global warming, such as western North America’s record heat of last summer. But it’s hard to tell if our projections are under-forecasting extreme heat.
In any case, the world must prepare for further possible record-shattering high temperatures in the months, years and decades to come. We need to rapidly decarbonise to limit the damage caused by future extreme events.