Tidal flooding

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October 17, 2016 tidal flooding on a sunny day, during the "king tides" in Brickell, Miami that peaked at 4 ft MLLW. October 17 2016 sunny day tidal flooding at Brickell Bay Drive and 12 Street downtown Miami, 4.34 MLLW high tide am.jpg
October 17, 2016 tidal flooding on a sunny day, during the "king tides" in Brickell, Miami that peaked at 4 ft MLLW.

Tidal flooding, also known as sunny day flooding [1] or nuisance flooding, [2] is the temporary inundation of low-lying areas, especially streets, during exceptionally high tide events, such as at full and new moons. The highest tides of the year may be known as the king tide, 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. [3]


This kind of flooding is becoming more common in cities and other human-occupied coastal areas as sea level rise associated with climate change and other human-related environmental impacts such as coastal erosion and land subsidence increase the vulnerability of infrastructure. [4] Geographies faced with these issues can utilize coastal management practices to mitigate the effects in some areas, but increasingly these kinds of floods may develop into coastal flooding that requires managed retreat or other more extensive climate change adaptation practices are needed for vulnerable areas.

The last remaining house on Holland Island that collapsed and was torn down in the 2010s as erosion and tides reached the foundation. Holland Island house.jpg
The last remaining house on Holland Island that collapsed and was torn down in the 2010s as erosion and tides reached the foundation.

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 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. [5]

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. [6] Further, regions with glaciers also experience sunny day flooding as climate change alters the dynamics of glacier meltwater. [6] 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. [6]

A warming climate causes physical changes to the types of ice on a glacier. [6] As glaciers retreat, there is less firn (water-retaining snow) so that more meltwater runs directly into the watershed over deeper, impervious glacial ice. [6]

Affected geographies

United States

High tide flooding, also called tidal flooding, has become much more common in the past seven decades. 1950- High tide flooding, by year - NOAA tide gauges (U.S.).svg
High tide flooding, also called tidal flooding, has become much more common in the past seven decades.

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. [8]

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 for example has disappeared over the years mainly due to subsidence and coastal erosion. [9] In the New Orleans area on the Gulf Coast of Louisiana, land subsidence results in the Grand Isle tide gauge showing an extreme upward sea level trend. [10]


Saltwater in drain on a bayfront street (Brickell Bay Drive) in Miami just up to street level; while not a direct flood, this inhibits normal passive, gravity-based drainage. Brickell Bay Drive drain at threshold of flooding during king tide 2016.jpg
Saltwater in drain on a bayfront street (Brickell Bay Drive) in Miami just up to street level; while not a direct flood, this inhibits normal passive, gravity-based drainage.

In Florida, controversy arose when state-level government mandated that the term "nuisance flooding" and other terms be used in place of terms such as sea level rise, climate change and global warming, prompting allegations of climate change denial, specifically against Governor Rick Scott. This amid Florida, specifically South Florida and the Miami metropolitan area 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. [11] The issue is more bipartisan in South Florida, particularly in places like Miami Beach, 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, formerly a mangrove wetland where the average elevation is less than one meter (3.3 feet).

In the Miami metropolitan area, where the vast majority of the land is below 10 ft (3.0 m), even a one-foot increase over the average high tide can cause widespread flooding. The 2015 and 2016 king tide event levels reached about 4 feet (1.2 m) MLLW, 3 feet (0.9 m) above mean sea level, or about 2 ft (0.61 m) NAVD88, and nearly the same above MHHW. [12] While the tide range is very small in Miami, averaging about 2 ft (0.61 m), with the greatest range being less than 2 m (6.6 ft), [13] the area is very acute to minute differences down to single inches due to the vast area at low elevation. NOAA tide gauge data for most stations shows current water level graphs relative to a fixed vertical datum, as well as mean sea level trends for some stations. During the king tides, the local Miami area tide gauge at Virginia Key shows levels running at times 1 foot (0.30 m) or more over datum.

Fort Lauderdale has installed over one hundred tidal valves since 2013 to combat flooding. Fort Lauderdale is nicknamed the "Venice of America" due to its roughly 165 miles (266 km) of canals. [14]

A recent University of Florida study correlated the increased tidal flooding in south Florida, at least from 2011–2015 to episodic atmospheric conditions. [15] The rate was about 3/4 of an inch (19 mm) per year, versus the global rate of just over a tenth of an inch (3 mm) per year. [16]

See also

Related Research Articles

<span class="mw-page-title-main">Coast</span> Area where land meets the sea or ocean

The coast, also known as the coastline or seashore, is defined as the area where land meets the ocean, or as a line that forms the boundary between the land and the coastline. Shores are influenced by the topography of the surrounding landscape, as well as by water induced erosion, such as waves. The geological composition of rock and soil dictates the type of shore which is created. The Earth has around 620,000 kilometres (390,000 mi) of coastline. Coasts are important zones in natural ecosystems, often home to a wide range of biodiversity. On land, they harbor important ecosystems such as freshwater or estuarine wetlands, which are important for bird populations and other terrestrial animals. In wave-protected areas they harbor saltmarshes, mangroves or seagrasses, all of which can provide nursery habitat for finfish, shellfish, and other aquatic species. Rocky shores are usually found along exposed coasts and provide habitat for a wide range of sessile animals and various kinds of seaweeds. In physical oceanography, a shore is the wider fringe that is geologically modified by the action of the body of water past and present, while the beach is at the edge of the shore, representing the intertidal zone where there is one. Along tropical coasts with clear, nutrient-poor water, coral reefs can often be found between depths of 1–50 meters.

<span class="mw-page-title-main">Tide</span> Rise and fall of the sea level under astronomical gravitational influences

Tides are the rise and fall of sea levels caused by the combined effects of the gravitational forces exerted by the Moon and are also caused by the Earth and Moon orbiting one another.

<span class="mw-page-title-main">Sea level</span> Geographical reference point from which various heights are measured

Mean sea level is an average surface level of one or more among Earth's coastal bodies of water from which heights such as elevation may be measured. The global MSL is a type of vertical datum – a standardised geodetic datum – that is used, for example, as a chart datum in cartography and marine navigation, or, in aviation, as the standard sea level at which atmospheric pressure is measured to calibrate altitude and, consequently, aircraft flight levels. A common and relatively straightforward mean sea-level standard is instead the midpoint between a mean low and mean high tide at a particular location.

<span class="mw-page-title-main">Estuary</span> Partially enclosed coastal body of brackish water

An estuary is a partially enclosed coastal body of brackish water with one or more rivers or streams flowing into it, and with a free connection to the open sea. Estuaries form a transition zone between river environments and maritime environments and are an example of an ecotone. Estuaries are subject both to marine influences such as tides, waves, and the influx of saline water, and to fluvial influences such as flows of freshwater and sediment. The mixing of seawater and freshwater provides high levels of nutrients both in the water column and in sediment, making estuaries among the most productive natural habitats in the world.

<span class="mw-page-title-main">Barrier island</span> Coastal dune landform that forms by wave and tidal action parallel to the mainland coast

Barrier islands are a coastal landforms—a type of dune system and sand island—where an area of sand has been formed by wave and tidal action parallel to the mainland coast. They usually occur in chains, consisting of anything from a few islands to more than a dozen. They are subject to change during storms and other action, but absorb energy and protect the coastlines and create areas of protected waters where wetlands may flourish. A barrier chain may extend for hundreds of kilometers, with islands periodically separated by tidal inlets. The largest barrier island in the world is Padre Island of Texas, United States, at 113 miles (182 km) long. Sometimes an important inlet may close permanently, transforming an island into a peninsula, thus creating a barrier peninsula, often including a beach, barrier beach. Though many are long and narrow, the length and width of barriers and overall morphology of barrier coasts are related to parameters including tidal range, wave energy, sediment supply, sea-level trends, and basement controls. The amount of vegetation on the barrier has a large impact on the height and evolution of the island.

A rip tide, or riptide, is a strong offshore current that is caused by the tide pulling water through an inlet along a barrier beach, at a lagoon or inland marina where tide water flows steadily out to sea during ebb tide. It is a strong tidal flow of water within estuaries and other enclosed tidal areas. The riptides become the strongest where the flow is constricted. When there is a falling or ebbing tide, the outflow water is strongly flowing through an inlet toward the sea, especially once stabilized by jetties.

<span class="mw-page-title-main">Storm surge</span> Rise of water associated with a low-pressure weather system

A storm surge, storm flood, tidal surge, or storm tide is a coastal flood or tsunami-like phenomenon of rising water commonly associated with low-pressure weather systems, such as cyclones. It is measured as the rise in water level above the normal tidal level, and does not include waves.

<span class="mw-page-title-main">Tidal creek</span> Inlet or estuary that is affected by ebb and flow of ocean tides

A tidal creek or tidal channel is a narrow inlet or estuary that is affected by the ebb and flow of ocean tides. Thus, it has variable salinity and electrical conductivity over the tidal cycle, and flushes salts from inland soils. Tidal creeks are characterized by slow water velocity, resulting in buildup of fine, organic sediment in wetlands. Creeks may often be a dry to muddy channel with little or no flow at low tide, but with significant depth of water at high tide. Due to the temporal variability of water quality parameters within the tidally influenced zone, there are unique biota associated with tidal creeks which are often specialised to such zones. Nutrients and organic matter are delivered downstream to habitats normally lacking these, while the creeks also provide access to inland habitat for salt-water organisms.

<span class="mw-page-title-main">Tidal range</span> Vertical difference between the high tide and the succeeding low tide

Tidal range is the difference in height between high tide and low tide. Tides are the rise and fall of sea levels caused by gravitational forces exerted by the Moon and Sun, by Earth's rotation and by centrifugal force caused by Earth's progression around the Earth-Moon barycenter. Tidal range depends on time and location.

A tidal river is a river whose flow and level are caused by tides. A section of a larger river affected by the tides is a tidal reach, but it may sometimes be considered a tidal river if it had been given a separate and another title name.

The effects of climate change in Florida are attributable to man-made increases in atmospheric carbon dioxide. Floridians are experiencing increased flooding due to sea level rise, and are concerned about the possibility of more frequent or more intense hurricanes.

<span class="mw-page-title-main">Sea level rise</span> Rise in sea levels due to climate change

Between 1901 and 2018, the average global sea level rose by 15–25 cm (6–10 in), or an average of 1–2 mm per year. This rate accelerated to 4.62 mm/yr for the decade 2013–2022. Climate change due to human activities is the main cause. Between 1993 and 2018, thermal expansion of water accounted for 42% of sea level rise. Melting temperate glaciers accounted for 21%, with Greenland accounting for 15% and Antarctica 8%. Sea level rise lags changes in the Earth's temperature. So sea level rise will continue to accelerate between now and 2050 in response to warming that is already happening. What happens after that will depend on what happens with human greenhouse gas emissions. Sea level rise may slow down between 2050 and 2100 if there are deep cuts in emissions. It could then reach a little over 30 cm (1 ft) from now by 2100. With high emissions it may accelerate. It could rise by 1 m or even 2 m by then. In the long run, sea level rise would amount to 2–3 m (7–10 ft) over the next 2000 years if warming amounts to 1.5 °C (2.7 °F). It would be 19–22 metres (62–72 ft) if warming peaks at 5 °C (9.0 °F).

<span class="mw-page-title-main">Climate of Miami</span> Overview of the climate of Miami

The climate of Miami is classified as having a tropical monsoon climate with hot and humid summers; short, warm winters; and a marked drier season in the winter. Its sea-level elevation, coastal location, position just above the Tropic of Cancer, and proximity to the Gulf Stream shape its climate.

<span class="mw-page-title-main">North Shore (Oahu)</span> Coast of Oʻahu

The North Shore, in the context of geography of the Island of Oʻahu, refers to the north-facing coastal area of Oʻahu between Kaʻena Point and Kahuku. The largest settlement is Haleʻiwa.

<span class="mw-page-title-main">Coastal flooding</span> Type of natural disaster

Coastal flooding occurs when dry and low-lying land is submerged (flooded) by seawater. The range of a coastal flooding is a result of the elevation of floodwater that penetrates the inland which is controlled by the topography of the coastal land exposed to flooding. The seawater can flood the land via several different paths: direct flooding, overtopping of a barrier, or breaching of a barrier. Coastal flooding is largely a natural event. Due to the effects of climate change and an increase in the population living in coastal areas, the damage caused by coastal flood events has intensified and more people are being affected.

<span class="mw-page-title-main">New York Harbor Storm-Surge Barrier</span> Proposed barrier/floodgate system to protect New York metro area

The New York Harbor Storm-Surge Barrier is a proposed flood barrier system to protect the New York-New Jersey Harbor Estuary from storm surges. The proposed system would consist of one barrier located across the mouth of Lower New York Bay, possibly between Sandy Hook (N.J.) and Rockaway (N.Y.), and a second on the upper East River to provide a ring of protection to most of the bi-state region. Through extensive use of floodgates, both barriers would have largely open cross-sections during normal conditions to minimize environmental impacts on the estuary and port operations.

<span class="mw-page-title-main">Climate change in Maryland</span> Climate change in the US state of Maryland

Climate change in Maryland encompasses the effects of climate change, attributed to man-made increases in atmospheric carbon dioxide, in the U.S. state of Maryland.

<span class="mw-page-title-main">Climate change in Virginia</span> Climate change in the US state of Virginia

Climate change in Virginia encompasses the effects of climate change, attributed to man-made increases in atmospheric carbon dioxide, in the U.S. state of Virginia.

<span class="mw-page-title-main">Hapua</span>

A hapua is a river-mouth lagoon on a mixed sand and gravel (MSG) beach, formed at the river-coast interface where a typically braided, although sometimes meandering, river interacts with a coastal environment that is significantly affected by longshore drift. The lagoons which form on the MSG coastlines are common on the east coast of the South Island of New Zealand and have long been referred to as hapua by the Māori. This classification differentiates hapua from similar lagoons located on the New Zealand coast termed waituna.

<span class="mw-page-title-main">Sedimentation enhancing strategy</span>

Sedimentation enhancing strategies are environmental management projects aiming to restore and facilitate land-building processes in deltas. Sediment availability and deposition are important because deltas naturally subside and therefore need sediment accumulation to maintain their elevation, particularly considering increasing rates of sea-level rise. Sedimentation enhancing strategies aim to increase sedimentation on the delta plain primarily by restoring the exchange of water and sediments between rivers and low-lying delta plains. Sedimentation enhancing strategies can be applied to encourage land elevation gain to offset sea-level rise. Interest in sedimentation enhancing strategies has recently increased due to their ability to raise land elevation, which is important for the long-term sustainability of deltas.


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