Tidal flooding, also known as sunny day flooding or nuisance flooding, is the temporary inundation of low-lying areas, especially streets, during exceptionally

high tide Tides are the rise and fall of sea levels caused by the combined effects of the gravitational forces exerted by the Moon (and to a much lesser extent, the Sun) and are also caused by the Earth and Moon orbiting one another. Tide tables ...

events, such as at full and

new moon In astronomy, the new moon is the first lunar phase, when the Moon and Sun have the same ecliptic longitude. At this phase, the lunar disk is not visible to the naked eye, except when it is silhouetted against the Sun during a solar eclipse. ...

s. The highest tides of the year may be known as the

king tide A king tide is an especially high spring tide, especially the perigean spring tides which occur three or four times a year. King tide is not a scientific term, nor is it used in a scientific context. The expression originated in Australia, Ne ...

, with the month varying by location. These kinds of floods tend not to be a high risk to property or human safety, but further stress coastal infrastructure in low-lying areas. This kind of flooding is becoming more common in cities and other human-occupied coastal areas as

sea level rise The sea level has been rising from the end of the last ice age, which was around 20,000 years ago. Between 1901 and 2018, the average sea level rose by , with an increase of per year since the 1970s. This was faster than the sea level had e ...

associated with

climate change Present-day climate change includes both global warming—the ongoing increase in Global surface temperature, global average temperature—and its wider effects on Earth's climate system. Climate variability and change, Climate change in ...

and other human-related environmental impacts such as

coastal erosion Coastal erosion is the loss or displacement of land, or the long-term removal of sediment and rocks along the coastline due to the action of Wind wave, waves, Ocean current, currents, tides, wind-driven water, waterborne ice, or other impacts ...

and land subsidence increase the vulnerability of infrastructure. Geographies faced with these issues can utilize

coastal management Coastal management is defence against flooding and erosion, and techniques that stop erosion to claim lands. Protection against rising sea levels in the 21st century is crucial, as sea level rise accelerates due to climate change. Changes in s ...

practices to mitigate the effects in some areas, but increasingly these kinds of floods may develop into

coastal flooding Coastal flooding occurs when dry and low-lying land is submerged (flooded) by seawater. The range of a coastal Flood, flooding is a result of the elevation of floodwater that penetrates the inland which is controlled by the topography of the coas ...

that requires

managed retreat Managed retreat involves the purposeful, coordinated movement of people and buildings away from risks. This may involve the movement of a person, infrastructure (e.g., building or road), or community. It can occur in response to a variety of hazar ...

or other more extensive

climate change adaptation Climate change adaptation is the process of adjusting to the effects of climate change, both current and anticipated.IPCC, 2022Annex II: Glossary

Effects on infrastructure

Tidal flooding is capable of greatly inhibiting natural gravity-based drainage systems in low-lying areas when it reaches levels that are below visible inundation of the surface, but which are high enough to incapacitate the lower drainage or sewer system. Thus, even normal rainfall or storm surge">sewerage">sewer system. Thus, even normal rainfall or storm surge events can cause greatly amplified flooding effects. One passive solution to intrusion through drainage systems are one way back-flow valves in drainage ways. However, while this may prevent a majority of the tidal intrusion, it also inhibits drainage during exceptionally high tides that shut the valves. In Miami Beach, where resilience work is underway, the pump systems replace insufficient gravity-based systems.

Relation to climate change

Sunny day flooding is often associated with coastal regions, where sea level rise attributed to global warming can send water into the streets on days with elevated high tides. Further, regions with glaciers also experience sunny day flooding as climate change alters the dynamics of glacier meltwater. Abnormally hot temperatures not only swell rivers and creeks directly through accelerated snowmelt, but can burst ice dams and cause water from glacial lakes to swell waterways less predictably. A warming climate causes physical changes to the types of ice on a glacier. As glaciers retreat, there is less wikt:firn">firn __NOTOC__ Firn (; from Swiss German "last year's", cognate with ''before'') is partially compacted névé, a type of snow that has been left over from past seasons and has been recrystallized into a substance denser than névé. It is ice that ...

(water-retaining snow) so that more meltwater runs directly into the watershed over deeper, impervious glacial ice.

Affected geographies

United States

Most of the coastal communities in the Eastern Seaboard of the United States are vulnerable to this kind of flooding as sea level rise increases. Due to changing geography such as subsidence, and poorly planned development, tidal flooding may exist separate from modern nuisance flooding associated with sea level rise and anthropocentric climate change. The widely publicized Holland Island in

Maryland Maryland ( ) is a U.S. state, state in the Mid-Atlantic (United States), Mid-Atlantic region of the United States. It borders the states of Virginia to its south, West Virginia to its west, Pennsylvania to its north, and Delaware to its east ...

for example has disappeared over the years mainly due to subsidence and

. In the

New Orleans New Orleans (commonly known as NOLA or The Big Easy among other nicknames) is a Consolidated city-county, consolidated city-parish located along the Mississippi River in the U.S. state of Louisiana. With a population of 383,997 at the 2020 ...

area on the

Gulf Coast The Gulf Coast of the United States, also known as the Gulf South or the South Coast, is the coastline along the Southern United States where they meet the Gulf of Mexico. The coastal states that have a shoreline on the Gulf of Mexico are Tex ...

Louisiana Louisiana ( ; ; ) is a state in the Deep South and South Central regions of the United States. It borders Texas to the west, Arkansas to the north, and Mississippi to the east. Of the 50 U.S. states, it ranks 31st in area and 25 ...

, land subsidence results in the Grand Isle tide gauge showing an extreme upward sea level trend.

Florida

Florida Florida ( ; ) is a U.S. state, state in the Southeastern United States, Southeastern region of the United States. It borders the Gulf of Mexico to the west, Alabama to the northwest, Georgia (U.S. state), Georgia to the north, the Atlantic ...

, controversy arose when state-level government mandated that the term "nuisance flooding" and other terms be used in place of terms such as

and

global warming Present-day climate change includes both global warming—the ongoing increase in global average temperature—and its wider effects on Earth's climate system. Climate change in a broader sense also includes previous long-term changes ...

, prompting allegations of

climate change denial Climate change denial (also global warming denial) is a form of science denial characterized by rejecting, refusing to acknowledge, disputing, or fighting the scientific consensus on climate change. Those promoting denial commonly use rhetor ...

, specifically against

Governor A governor is an politician, administrative leader and head of a polity or Region#Political regions, political region, in some cases, such as governor-general, governors-general, as the head of a state's official representative. Depending on the ...

Rick Scott Richard Lynn Scott ( Myers; born December 1, 1952) is an American attorney, businessman, politician, and United States Navy, Navy veteran serving as the Seniority in the United States Senate, senior United States senator from the state of F ...

. This amid Florida, specifically

South Florida South Florida, sometimes colloquially shortened to SoFlo, is the Regions of the United States#Florida, southernmost region of the U.S. state of Florida. It is one of Florida's three most commonly referred to directional regions; the two others are ...

and the

Miami metropolitan area The Miami metropolitan area is a coastal metropolitan area in southeastern Florida. It is the sixth-largest metropolitan statistical area (MSA) in the United States, the fifth-largest metropolitan area in the Southern United States, and the lar ...

being one of the most at risk areas in the world for the potential effects of sea level rise, and where the frequency and severity of tidal flooding events increased in the 21st century. The issue is more bipartisan in South Florida, particularly in places like

Miami Beach Miami Beach is a coastal resort city in Miami-Dade County, Florida, United States. It is part of the Miami metropolitan area of South Florida. The municipality is located on natural and human-made barrier islands between the Atlantic Ocean an ...

, where a several hundred million dollar project is underway to install more than 50 pumps and physically raise roads to combat the flooding, mainly along the west side of

South Beach South Beach, also nicknamed colloquially as SoBe, is a Neighborhoods of Miami Beach, Florida, neighborhood in Miami Beach, Florida. It is located east of Miami between Biscayne Bay and the Atlantic Ocean. The area encompasses Miami Beach south ...

, formerly a mangrove wetland where the average elevation is less than . In the

, where the vast majority of the land is below , even a one-foot increase over the average high tide can cause widespread flooding. The 2015 and 2016

event levels reached about MLLW, above

mean sea level A mean is a quantity representing the "center" of a collection of numbers and is intermediate to the extreme values of the set of numbers. There are several kinds of means (or "measures of central tendency") in mathematics, especially in statist ...

, or about NAVD88, and nearly the same above MHHW. While the tide range is very small in Miami, averaging about , with the greatest range being less than , the area is very acute to minute differences down to single inches due to the vast area at low elevation. NOAA

tide gauge A tide gauge is a device for measuring the change in sea level relative to a vertical datum. It is also known as a mareograph, marigraph, and sea-level recorder. When applied to freshwater continental water body, water bodies, the instrument may ...

data for most stations shows current water level graphs relative to a fixed

vertical datum In geodesy, surveying, hydrography and navigation, vertical datum or altimetric datum is a reference coordinate surface used for vertical positions, such as the elevations of Earth-bound features (terrain, bathymetry, water level, and built stru ...

, as well as mean sea level trends for some stations. During the king tides, the local Miami area tide gauge at

Virginia Key Virginia Key is an barrier island in Miami, Florida. It is located in Biscayne Bay south of Brickell and north of Key Biscayne and is accessible from the mainland via the Rickenbacker Causeway. The island is mainly occupied by the Virginia Ke ...

shows levels running at times or more over datum.

Fort Lauderdale Fort Lauderdale ( ) is a coastal city located in the U.S. state of Florida, north of Miami along the Atlantic Ocean. It is the county seat of and most populous city in Broward County with a population of 182,760 at the 2020 census, making it ...

has installed over one hundred tidal valves since 2013 to combat flooding. Fort Lauderdale is nicknamed the "Venice of America" due to its roughly of canals. A recent

University of Florida The University of Florida (Florida or UF) is a public university, public land-grant university, land-grant research university in Gainesville, Florida, United States. It is a senior member of the State University System of Florida and a preem ...

study correlated the increased tidal flooding in south Florida, at least from 2011–2015 to episodic atmospheric conditions. The rate was about per year, versus the global rate of just over per year.

References

External links

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Water Levels for Virginia Key Tide Gauge (Miami)

South Florida's Rising Seas - Sea Level Rise Documentary
South Florida PBS {{Commons category, Tidal flooding Tides Flood