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]

Contents

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

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. [7]

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. [8] 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. [9]

Florida

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.
20201112 Tidal flooding graph - Annapolis, Maryland.svg
The extent of tidal flooding varies by region, with the Chesapeake Bay town of Annapolis, Maryland having an annual tidal flooding profile substantially affected by sea level rise caused by climate change. [10]

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

Coast 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 ocean or a lake. 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. Along tropical coasts with clear, nutrient-poor water, coral reefs can often be found between depths of 1–50 m.

Flood Natural disaster caused by water overflow

A flood is an overflow of water that submerges land that is usually dry. In the sense of "flowing water", the word may also be applied to the inflow of the tide. Floods are an area of study of the discipline hydrology and are of significant concern in agriculture, civil engineering and public health. Human changes to the environment often increase the intensity and frequency of flooding, for example land use changes such as deforestation and removal of wetlands, changes in waterway course or flood controls such as with levees, and larger environmental issues such as climate change and sea level rise. In particular climate change's increased rainfall and extreme weather events increases the severity of other causes for flooding, resulting in more intense floods and increased flood risk.

Sea level 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.

Estuary 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.

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. During these falling and ebbing tides, a riptide can carry a person far offshore. For example, the ebbing tide at Shinnecock Inlet in Southampton, New York, extends more than 300 metres (980 ft) offshore. Because of this, riptides are typically more powerful than rip currents.

Storm surge Rise of water surface 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.

Tidal creek 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 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.

Tidal range 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 and the rotation of Earth. Tidal range depends on time and location.

Climate change in the United States Emissions, impacts and responses of the United States related to climate change

The climate of the United States is changing in ways that are widespread and varied. From 2010 to 2019, the United States experienced its hottest decade on record. Different regions experience widely different climatic changes. Changes in climate in the regions of the United States appear significant. For example, drought conditions appear to be worsening in the southwest while improving in the northeast. Generally, states that emit more carbon dioxide per person and prevent climate action are suffering more.

Climate change in Florida Climate change in the US state of Florida

The effects of Climate change in Florida is 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.

Sea level rise Current and projected rise in sea levels due to climate change

Tide gauge measurements show that the current global sea level rise began at the start of the 20th century. Between 1901 and 2018, the globally averaged sea level rose by 15–25 cm (6–10 in). More precise data gathered from satellite radar measurements reveal an accelerating rise of 7.5 cm (3 in) from 1993 to 2017, for an average rate of 3.1 cm per decade. This acceleration is due mostly to climate change, which heats the ocean and which melts the land-based ice sheets and glaciers. Between 1993 and 2018, the thermal expansion of water contributed 42% to sea level rise; melting of temperate glaciers, 21%; Greenland, 15%; and Antarctica, 8%. Climate scientists expect the rate to further accelerate during the 21st century, with the latest measurements saying the sea levels are rising by 3.7 mm per year.

Climate of Miami 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.

North Shore (Oahu) 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.

Coastal flooding Type of natural disaster

Coastal flooding normally occurs when dry and low-lying land is submerged 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. Flood damage modelling was limited to local, regional or national scales. However, with the presence of climate change and an increase in the population rates, flood events have intensified and called for a global interest in finding out different methods with both spatial and temporal dynamics.

Coastal Risk Consulting Climate adaptation startup

Coastal Risk Consulting, LLC. is an American startup climate adaptation technology and consulting company with headquarters in Plantation, Florida. Coastal Risk provides individuals, businesses, and local governments with climate impact modeling technology, available as an online software-as-a-service (SaaS), that allows property owners to assess their vulnerability to flooding related to sea level rise and climate change impacts and assists in adaptation and resiliency decision-making.

Climate change in Delaware Climate change in the US state of Delaware

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

Climate change in South Carolina Climate change in the US state of South Carolina

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

Climate change in Virginia Climate change in the US state of Virginia

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Sinking cities

Sinking cities are urban environments that are in danger of disappearing due to their rapidly changing landscapes. The largest contributors to these cities becoming unlivable are the combined effects of climate change, land subsidence, and accelerated urbanization. Many of the world's largest and most rapidly growing cities are located along rivers and coasts, exposing them to natural disasters. As countries continue to invest people, assets, and infrastructure into these cities, the loss potential in these areas also increases. Sinking cities must overcome substantial barriers to properly prepare for today's dynamic environmental climate.

Sedimentation enhancing strategy

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.

References

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  3. "What is nuisance flooding? Defining and monitoring an emerging challenge | PreventionWeb.net". www.preventionweb.net. Retrieved 2021-01-07.
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  8. Wheeler, Timothy B. (October 22, 2010). "Holland Island house collapse 'end of an era'". The Baltimore Sun . Retrieved November 2, 2016.
  9. "Mean Sea Level Trend 8761724 Grand Isle, Louisiana". NOAA. Retrieved November 24, 2016.
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  11. Wdowinski, Shimon; Bray, Ronald; Kirtman, Ben P.; Wu, Zhaohua (2016). "Increasing flooding hazard in coastal communities due to rising sea level: Case study of Miami Beach, Florida". Ocean & Coastal Management. 126: 1–8. doi:10.1016/j.ocecoaman.2016.03.002.
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  16. Pam Wright (August 10, 2017). "Sea Levels Have Risen Faster in Southeast U.S., and Scientists Think They Know Why". The Weather Channel . Retrieved August 10, 2017.