Flooding from Hurricane Ida in September 2021 caused the deaths of dozens of people in four different states, as well as millions, if not billions of dollars in damage. It’s just the latest in a string of devastating storms to hit over the last two decades.
When hurricanes and tropical storms make landfall, they bring high winds, storm surge, and lots of rain. Flooding is often considered the deadliest part of a hurricane; the National Hurricane Center estimates that 75% of all deaths from hurricanes between 1963 - 2012 can be attributed to storm surges and rainfall flooding.
Coastal flooding isn’t limited to tropical storms and hurricanes, however. Rising sea levels due to climate change are expected to cause more frequent flood events. Here’s how coastal flooding is anticipated to impact humans and coastal communities in the coming decade.
Causes of coastal flooding
There are two main types of coastal floods: those caused by storms (e.g., catastrophic coastal flooding), and those caused by sea-level rise (e.g., “nuisance flooding”). Nuisance floods are defined by the CDC as “recurring, minor floods that happen when water levels exceed local thresholds defined by the National Oceanic and Atmospheric Administration (NOAA) – generally about 1.5 feet above the historical average daily high water maximum.”
Coastal flooding is generally caused by four main factors.
Climate change has caused sea levels to rise dramatically over the last 20 years. As the planet gets hotter, ocean water expands and melting glaciers and ice sheets melt, adding more freshwater into the oceans. Some estimates expect sea levels to rise another 12 to 60 inches, depending on the future rise in global temperature, by 2100. Climate change and sea level rise are a big deal everywhere, and especially in the US — where nearly 40% of the population lives in high population-density coastal areas. A huge percentage of the population is at risk for flooding.
Severe storms also cause a huge amount of flooding due to storm surges and rainfall. Hurricanes are becoming more intense, bringing more rain and water to low-lying coastal areas.
Hurricane Ida is only the most recent example of just how much damage a storm surge can do. In 2012, Hurricane Sandy caused more than $200 billion in damage primarily in New York and New Jersey. One study predicts that storm surge flooding could be as much as 17 times more frequent in the area’s coastal regions by 2100.
Rainfall is also becoming more intense due to climate change. “Even rainier storms are predicted for the future, with tomorrow’s hurricanes expected to be as much as 37 percent wetter near their center and about 20 percent wetter as much as 60 miles away,” wrote the NRDC.
Changing precipitation patterns
A further impact of climate change is increased evaporation. Higher temperatures lead to more evaporation and greater overall precipitation. Already the U.S. is getting 6% more precipitation than it did 100 years ago.
And, data shows that patterns are changing: areas in higher latitudes are seeing an increase in precipitation, while those closer to the equator are becoming drier. For areas not used to heavy rain, the infrastructure may not be built to drain or withstand flooding sufficiently. Coastal communities that experience increased precipitation may be less equipped to handle storms that follow.
Finally, human activities contribute to increased flooding. From building dams, levees, and reservoirs to increased urbanization (e.g., adding pavement that prevents water from draining), human activities alter natural drainage systems, remove natural barriers to storm surges, and develop floodplains. Undermaintained infrastructure also contributes to flooding.
How does a coastal flood impact our communities?
Flooding — even so-called “nuisance” flooding — upends lives and causes billions of dollars in damages. At worst, flooding can lead to death. Drowning in floodwaters was the leading cause of death associated with hurricanes and coastal storms from 1963 to 2012. Coastal flooding is considered an indiscriminate natural disaster, meaning it impacts everyone no matter their wealth or socio-economic standing.
Floods are also one of the most expensive natural disasters. Between 2007 and 2017, the National Flood Insurance Program (NFIP) paid an average of $2.9 billion per year to cover flood-related losses, with certain years costing far more.
But, the long-term impacts of flooding go far beyond economic recovery. “Flooding also brings contamination and disease. Floodwaters can carry raw sewage, leaked toxic chemicals, and runoff from hazardous waste sites and factory farms,” wrote the NRDC. “They can pollute drinking water supplies and cause eye, ear, skin, and gastrointestinal infections. When floodwaters recede, bacteria and mold may remain, increasing rates of respiratory illnesses, such as asthma. Flooding can also contribute to mental health problems, lead to economic loss (as in the form of lost business or wages), and uproot whole communities.”
Many times, it’s the same communities that are repeatedly impacted by coastal flooding. One study found that more than 30,000 properties flooded an average of five times each. Without the proper preparation, flooding is only going to continue — and get worse.
How to prepare for coastal flooding
Sofar Ocean's modular hardware collects ocean data at scale: with the largest private network of drifting buoys in the world, Sofar's forecasts can predict marine weather with 50% more accuracy than NOAA and ECMWF. The global grid of Spotters stretches across all five oceans with a myriad of applications.
Individually, the systems can optimize hurricane forecasts, improve flood maps, hasten hazard warnings, and validate sea-level rise models. Anchored with a Smart Mooring, a Spotter can be equipped with any oceanographic sensor anywhere in the ocean for immediate upload to the cloud, enabling ocean discoveries no matter the conditions.
Today, just over 50% of flood maps in the US are considered to be obsolete, preventing communities from understanding the risks involved in future development, discounting the risk of flooding, and limiting evacuation preparedness. In coastal communities, strong warning systems are crucial to providing people with enough time to evacuate, shelter in place, or receive aid after a storm has made landfall.
Luckily, engineers and oceanographers innovate with these conditions in mind: Sofar Ocean’s Smart Mooring includes a pressure sensor to measure water level and capture storm surges. Experts can continually take the pulse of the sea state, detect incoming storms and get ahead of flood risks. Strategies and decisions can then be made according to data patterns or irregularities, rather than guesswork.
To learn more about mitigating the risks of flooding, visit the Sofar Ocean blog.