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98-623: The Worcester Flood Diversion Channel is a flood control channel located in Auburn and Millbury, Massachusetts . It was built by the United States Army Corps of Engineers because of the Flood Control Act of 1944 . Its aim was to protect the city of Worcester, Massachusetts from future floods, as previous flooding had caused much damage to the city. It consists of a series of dams, reservoirs, and channels. During

196-446: A canal's full capacity may cause flooding to spread to other waterways and areas of the community, which causes damage. Defenses (both long-term and short-term) can be constructed to minimize damage, which involves raising the edge of the water with levees , embankments or walls. The high population and value of infrastructure at risk often justifies the high cost of mitigation in larger urban areas. The most effective way of reducing

294-430: A wave shoaling process described below. A tsunami can occur in any tidal state and even at low tide can still inundate coastal areas. On April 1, 1946, the 8.6 M w   Aleutian Islands earthquake occurred with a maximum Mercalli intensity of VI ( Strong ). It generated a tsunami which inundated Hilo on the island of Hawaii with a 14-metre high (46 ft) surge. Between 165 and 173 were killed. The area where

392-659: A 1 in 1000 year flood (light blue) and low-lying areas in need of flood defence (purple). The most sustainable way of reducing risk is to prevent further development in flood-prone areas and old waterways. It is important for at-risk communities to develop a comprehensive Floodplain Management plan. In the US, communities that participate in the National Flood Insurance Program must agree to regulate development in flood-prone areas. One way of reducing

490-525: A certain amount of space in which floodwaters can fill. Other beneficial uses of dam created reservoirs include hydroelectric power generation, water conservation , and recreation. Reservoir and dam construction and design is based upon standards, typically set out by the government. In the United States, dam and reservoir design is regulated by the US Army Corps of Engineers (USACE). Design of

588-556: A coast). The spawning grounds for fish and other wildlife habitats can become polluted or completely destroyed. Some prolonged high floods can delay traffic in areas which lack elevated roadways. Floods can interfere with drainage and economical use of lands, such as interfering with farming. Structural damage can occur in bridge abutments , bank lines, sewer lines, and other structures within floodways. Waterway navigation and hydroelectric power are often impaired. Financial losses due to floods are typically millions of dollars each year, with

686-517: A dam and reservoir follows guidelines set by the USACE and covers topics such as design flow rates in consideration to meteorological, topographic, streamflow, and soil data for the watershed above the structure. The term dry dam refers to a dam that serves purely for flood control without any conservation storage (e.g. Mount Morris Dam , Seven Oaks Dam ). Flood control channels are large and empty basins where surface water can flow through but

784-427: A few minutes at a time. The Tauredunum event was a large tsunami on Lake Geneva in 563 CE, caused by sedimentary deposits destabilised by a landslide. In the 1950s, it was discovered that tsunamis larger than had previously been believed possible can be caused by giant submarine landslides . These large volumes of rapidly displaced water transfer energy at a faster rate than the water can absorb. Their existence

882-417: A flood does happen, the city can recover quickly and costs are minimized. For example, homes can be put on stilts, electrical and HVAC equipment can be put on the roof instead of in the basement, and subway entrances and tunnels can have built-in movable water barriers. New York City began a substantial effort to plan and build for flood resilience after Hurricane Sandy . Flood resilience technologies support

980-432: A huge wave. As the tsunami approaches the coast and the waters become shallow, wave shoaling compresses the wave and its speed decreases below 80 kilometres per hour (50 mph). Its wavelength diminishes to less than 20 kilometres (12 mi) and its amplitude grows enormously—in accord with Green's law . Since the wave still has the same very long period , the tsunami may take minutes to reach full height. Except for

1078-541: A large problem of awareness and preparedness, as exemplified by the eruption and collapse of Anak Krakatoa in 2018 , which killed 426 and injured thousands when no warning was available. It is still regarded that lateral landslides and ocean-entering pyroclastic currents are most likely to generate the largest and most hazardous waves from volcanism; however, field investigation of the Tongan event , as well as developments in numerical modelling methods, currently aim to expand

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1176-641: A lowhead dam, is most often used to create millponds , but on the Humber River in Toronto, a weir was built near Raymore Drive to prevent a recurrence of the flood damage caused by Hurricane Hazel in October 1954. The Leeds flood alleviation scheme uses movable weirs which are lowered during periods of high water to reduce the chances of flooding upstream. Two such weirs, the first in the UK, were installed on

1274-538: A massive landslide from Monte Toc entered the reservoir behind the Vajont Dam in Italy. The resulting wave surged over the 262-metre (860 ft)-high dam by 250 metres (820 ft) and destroyed several towns. Around 2,000 people died. Scientists named these waves megatsunamis . Some geologists claim that large landslides from volcanic islands, e.g. Cumbre Vieja on La Palma ( Cumbre Vieja tsunami hazard ) in

1372-405: A method of using water to control flooding was discovered. This was accomplished by containing 2 parallel tubes within a third outer tube. When filled, this structure formed a non-rolling wall of water that can control 80 percent of its height in external water depth, with dry ground behind it. Eight foot tall water filled barriers were used to surround Fort Calhoun Nuclear Generating Station during

1470-469: A portion of the facility. AquaFence consists of interlocking panels which are waterproof and puncture-resistant, can be bolted down to resist winds, and use the weight of floodwater to hold them in place. Materials include marine-grade batlic laminate, stainless steel, aluminum and reinforced PVC canvas. The panels are reusable and can be stored flat between uses. The technology was designed as an alternative to building seawalls or placing sandbags in

1568-577: A reference sea level. A large tsunami may feature multiple waves arriving over a period of hours, with significant time between the wave crests. The first wave to reach the shore may not have the highest run-up. About 80% of tsunamis occur in the Pacific Ocean, but they are possible wherever there are large bodies of water, including lakes. However, tsunami interactions with shorelines and the seafloor topography are extremely complex, which leaves some countries more vulnerable than others. For example,

1666-462: A ridge and a trough. In the case of a propagating wave like a tsunami, either may be the first to arrive. If the first part to arrive at the shore is the ridge, a massive breaking wave or sudden flooding will be the first effect noticed on land. However, if the first part to arrive is a trough, a drawback will occur as the shoreline recedes dramatically, exposing normally submerged areas. The drawback can exceed hundreds of metres, and people unaware of

1764-467: A significant tsunami, such as the 1977 Sumba and 1933 Sanriku events. Tsunamis have a small wave height offshore, and a very long wavelength (often hundreds of kilometres long, whereas normal ocean waves have a wavelength of only 30 or 40 metres), which is why they generally pass unnoticed at sea, forming only a slight swell usually about 300 millimetres (12 in) above the normal sea surface. They grow in height when they reach shallower water, in

1862-655: A transoceanic tsunami has not occurred within recorded history. Susceptible locations are believed to be the Big Island of Hawaii , Fogo in the Cape Verde Islands , La Reunion in the Indian Ocean , and Cumbre Vieja on the island of La Palma in the Canary Islands ; along with other volcanic ocean islands. This is because large masses of relatively unconsolidated volcanic material occurs on

1960-445: A tsunami can be calculated by obtaining the square root of the depth of the water in metres multiplied by the acceleration due to gravity (approximated to 10 m/s ). For example, if the Pacific Ocean is considered to have a depth of 5000 metres, the velocity of a tsunami would be √ 5000 × 10 = √ 50000 ≈ 224 metres per second (730 ft/s), which equates to a speed of about 806 kilometres per hour (501 mph). This

2058-434: A tsunami can be generated when thrust faults associated with convergent or destructive plate boundaries move abruptly, resulting in water displacement, owing to the vertical component of movement involved. Movement on normal (extensional) faults can also cause displacement of the seabed, but only the largest of such events (typically related to flexure in the outer trench swell ) cause enough displacement to give rise to

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2156-473: A tsunami, which is that of an extraordinarily high tidal bore . Tsunamis and tides both produce waves of water that move inland, but in the case of a tsunami, the inland movement of water may be much greater, giving the impression of an incredibly high and forceful tide. In recent years, the term "tidal wave" has fallen out of favour, especially in the scientific community, because the causes of tsunamis have nothing to do with those of tides , which are produced by

2254-629: A wide range of flood management methods including but are not limited to flood mapping and physical implication measures. Flood risk management looks at how to reduce flood risk and how to appropriately manage risks that are associated with flooding. Flood risk management includes mitigating and preparing for flooding disasters, analyzing risk, and providing a risk analysis system to mitigate the negative impacts caused by flooding. Flooding and flood risk are especially important with more extreme weather and sea level rise caused by climate change as more areas will be effected by flood risk. Flood mapping

2352-559: Is a broad term that includes measures to control or mitigate flood waters, such as actions to prevent floods from occurring or to minimize their impacts when they do occur. Flood management methods can be structural or non-structural: There are several related terms that are closely connected or encompassed by flood management. Flood management can include flood risk management, which focuses on measures to reduce risk, vulnerability and exposure to flood disasters and providing risk analysis through, for example, flood risk assessment . In

2450-575: Is a flood defense system designed to protect people and property from inland waterway floods caused by heavy rainfall, gales, or rapid melting snow. The SCFB can be built to protect residential properties and whole communities, as well as industrial or other strategic areas. The barrier system is constantly ready to deploy in a flood situation, it can be installed in any length and uses the rising flood water to deploy. When permanent defenses fail, emergency measures such as sandbags , inflatable impermeable sacks, or other temporary barriers are used. In 1988,

2548-681: Is a related but separate concept describing a broader set of strategies taken to reduce flood risk and potential impact while improving resilience against flood events. As climate change has led to increased flood risk an intensity, flood management is an important part of climate change adaptation and climate resilience . For example, to prevent or manage coastal flooding , coastal management practices have to handle natural processes like tides but also sea level rise due to climate change. The prevention and mitigation of flooding can be studied on three levels: on individual properties, small communities, and whole towns or cities. Flood management

2646-467: Is a series of waves in a water body caused by the displacement of a large volume of water, generally in an ocean or a large lake . Earthquakes , volcanic eruptions and underwater explosions (including detonations, landslides , glacier calvings , meteorite impacts and other disturbances) above or below water all have the potential to generate a tsunami. Unlike normal ocean waves, which are generated by wind , or tides , which are in turn generated by

2744-472: Is a tool used by governments and policy makers to delineate the borders of potential flooding events, allowing educated decisions to prevent extreme flooding events. Flood maps are useful to create documentation that allows policy makers to make informed decisions about flood hazards. Flood mapping also provides conceptual models to both the public and private sectors with information about flooding hazards. Flood mapping has been criticized in many areas around

2842-620: Is also accustomed to tsunamis, with earthquakes of varying magnitudes regularly occurring off the coast of the island. Tsunamis are an often underestimated hazard in the Mediterranean Sea and parts of Europe. Of historical and current (with regard to risk assumptions) importance are the 1755 Lisbon earthquake and tsunami (which was caused by the Azores–Gibraltar Transform Fault ), the 1783 Calabrian earthquakes , each causing several tens of thousands of deaths and

2940-562: Is also used to refer to the phenomenon because the waves most often are generated by seismic activity such as earthquakes. Prior to the rise of the use of the term tsunami in English, scientists generally encouraged the use of the term seismic sea wave rather than tidal wave . However, like tidal wave , seismic sea wave is not a completely accurate term, as forces other than earthquakes—including underwater landslides , volcanic eruptions, underwater explosions, land or ice slumping into

3038-496: Is designed to help accurately forecast the passage of tsunamis across oceans as well as how tsunami waves interact with shorelines. The term "tsunami" is a borrowing from the Japanese tsunami 津波 , meaning "harbour wave." For the plural, one can either follow ordinary English practice and add an s , or use an invariable plural as in the Japanese. Some English speakers alter the word's initial / ts / to an / s / by dropping

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3136-520: Is indicated and in such cases environmentally helpful solutions may provide solutions. Natural flooding has many beneficial environmental effects. This kind of flooding is usually a seasonal occurrence where floods help replenish soil fertility, restore wetlands and promote biodiversity . Flooding has many impacts. It damages property and endangers the lives of humans and other species. Rapid water runoff causes soil erosion and concomitant sediment deposition elsewhere (such as further downstream or down

3234-515: Is not favoured by the scientific community because it might give the false impression of a causal relationship between tides and tsunamis. Tsunamis generally consist of a series of waves, with periods ranging from minutes to hours, arriving in a so-called " wave train ". Wave heights of tens of metres can be generated by large events. Although the impact of tsunamis is limited to coastal areas, their destructive power can be enormous, and they can affect entire ocean basins. The 2004 Indian Ocean tsunami

3332-404: Is not retained (except during flooding ), or dry channels that run below the street levels of some larger cities , so that if a flash flood occurs the excess water can drain out along these channels into a river or other bodies of water . Flood channels are sometimes built on the former courses of natural waterways as a way to reduce flooding. Channelization of this sort was commonly done in

3430-791: Is now Shakespear Regional Park at the tip of the Whangaparāoa Peninsula in the Auckland Region of New Zealand ; the attempt failed. There has been considerable speculation about the possibility of using nuclear weapons to cause tsunamis near an enemy coastline. Nuclear testing in the Pacific Proving Ground by the United States generated poor results. In Operation Crossroads in July 1946, two 20-kilotonne-of-TNT (84 TJ) bombs were detonated, one in

3528-735: Is part of environmental engineering . It involves the management of water movement, such as redirecting flood run-off through the use of floodwalls and flood gates to prevent floodwaters from reaching a particular area. Flood mitigation is a related but separate concept describing a broader set of strategies taken to reduce flood risk and potential impact while improving resilience against flood events. These methods include prevention, prediction (which enables flood warnings and evacuation), proofing (e.g.: zoning regulations), physical control ( nature-based solutions and physical structures like dams and flood walls ) and insurance (e.g.: flood insurance policies). Flood relief methods are used to reduce

3626-426: Is the formula used for calculating the velocity of shallow-water waves. Even the deep ocean is shallow in this sense because a tsunami wave is so long (horizontally from crest to crest) by comparison. The reason for the Japanese name "harbour wave" is that sometimes a village's fishermen would sail out, and encounter no unusual waves while out at sea fishing, and come back to land to find their village devastated by

3724-430: The 1883 eruption of Krakatoa , and the 2022 Hunga Tonga–Hunga Ha'apai eruption . Over 20% of all fatalities caused by volcanism during the past 250 years are estimated to have been caused by volcanogenic tsunamis. Debate has persisted over the origins and source mechanisms of these types of tsunamis, such as those generated by Krakatoa in 1883, and they remain lesser understood than their seismic relatives. This poses

3822-688: The 1908 Messina earthquake and tsunami. The tsunami claimed more than 123,000 lives in Sicily and Calabria and is among the deadliest natural disasters in modern Europe. The Storegga Slide in the Norwegian Sea and some examples of tsunamis affecting the British Isles refer to landslide and meteotsunamis , predominantly and less to earthquake-induced waves. As early as 426 BC the Greek historian Thucydides inquired in his book History of

3920-436: The 2011 Missouri River Flooding . Instead of trucking in sandbag material for a flood, stacking it, then trucking it out to a hazmat disposal site, flood control can be accomplished by using the on site water. However, these are not fool proof. A 8 feet (2.4 m) high 2,000 feet (610 m) long water filled rubber flood berm that surrounded portions of the plant was punctured by a skid-steer loader and it collapsed flooding

4018-413: The Canary Islands , may be able to generate megatsunamis that can cross oceans, but this is disputed by many others. In general, landslides generate displacements mainly in the shallower parts of the coastline, and there is conjecture about the nature of large landslides that enter the water. This has been shown to subsequently affect water in enclosed bays and lakes, but a landslide large enough to cause

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4116-485: The River Aire in October 2017 at Crown Point, Leeds city centre and Knostrop . The Knostrop weir was operated during the 2019 England floods . They are designed to reduce potential flood levels by up to one metre. Coastal flooding is addressed with coastal defenses, such as sea walls , beach nourishment , and barrier islands . Tide gates are used in conjunction with dykes and culverts. They can be placed at

4214-530: The gravitational pull of the Moon and the Sun , a tsunami is generated by the displacement of water from a large event. Tsunami waves do not resemble normal undersea currents or sea waves because their wavelength is far longer. Rather than appearing as a breaking wave , a tsunami may instead initially resemble a rapidly rising tide . For this reason, it is often referred to as a tidal wave , although this usage

4312-427: The "t," since English does not natively permit /ts/ at the beginning of words, though the original Japanese pronunciation is /ts/ . The term has become commonly accepted in English, although its literal Japanese meaning is not necessarily descriptive of the waves, which do not occur only in harbours. Tsunamis are sometimes referred to as tidal waves . This once-popular term derives from the most common appearance of

4410-458: The 1960s, but is now often being undone, with "rechannelization" through meandering, vegetated, porous paths. This is because channellizing the flow in a concrete chute often made flooding worse. Water levels during a flood tend to rise, then fall, exponentially. The peak flood level occurs as a very steep, short spike; a quick spurt of water. Anything that slows the surface runoff (marshes, meanders, vegetation, porous materials, turbulent flow,

4508-818: The Great Lakes, the Aegean Sea, the English Channel, and the Balearic Islands, where they are common enough to have a local name, rissaga . In Sicily they are called marubbio and in Nagasaki Bay, they are called abiki . Some examples of destructive meteotsunamis include 31 March 1979 at Nagasaki and 15 June 2006 at Menorca, the latter causing damage in the tens of millions of euros. Meteotsunamis should not be confused with storm surges , which are local increases in sea level associated with

4606-477: The Pacific coasts of the United States and Mexico lie adjacent to each other, but the United States has recorded ten tsunamis in the region since 1788, while Mexico has recorded twenty-five since 1732. Similarly, Japan has had more than a hundred tsunamis in recorded history, while the neighbouring island of Taiwan has registered only two, in 1781 and 1867. All waves have a positive and negative peak; that is,

4704-597: The Peloponnesian War about the causes of tsunami, and was the first to argue that ocean earthquakes must be the cause. The oldest human record of a tsunami dates back to 479 BC , in the Greek colony of Potidaea , thought to be triggered by an earthquake. The tsunami may have saved the colony from an invasion by the Achaemenid Empire . The cause, in my opinion, of this phenomenon must be sought in

4802-450: The air over and one underwater within the shallow waters of the 50-metre (164 ft) deep lagoon at Bikini Atoll . The bombs detonated about 6 km (3.7 mi; 3.2 nmi) from the nearest island, where the waves were no higher than 3 to 4 m (9.8 to 13.1 ft) when they reached the shoreline. Other underwater tests, mainly Operation Hardtack I /Wahoo in deep water and Operation Hardtack I/Umbrella in shallow water, confirmed

4900-504: The amount of mitigation needed to protect humans and buildings from flooding events. Similarly, flood warning systems are important for reducing risks. Following the occurrence of flooding events, other measures such as rebuilding plans and insurance can be integrated into flood risk management plans. Flood risk management strategy diversification is needed to ensure that management strategies cover several different scenarios and ensure best practices. Flood risk management aims to reduce

4998-650: The building site, including scour protection for shoreline developments, improving rainwater in filtration through the use of permeable paving materials and grading away from structures, and inclusion of berms , wetlands or swales in the landscape. When more homes, shops and infrastructure are threatened by the effects of flooding, then the benefits of protection are worth the additional cost. Temporary flood defenses can be constructed in certain locations which are prone to floods and provide protection from rising flood waters. Rivers running through large urban developments are often controlled and channeled. Water rising above

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5096-601: The capacity of stormwater systems. This separates stormwater from blackwater , so that overflows in peak periods do not contaminate rivers. One example is the SMART Tunnel in Kuala Lumpur. Some methods of flood control have been practiced since ancient times. These methods include planting vegetation to retain extra water, terracing hillsides to slow flow downhill, and the construction of floodways (man-made channels to divert floodwater). Other techniques include

5194-417: The construction of levees, lakes, dams, reservoirs, retention ponds to hold extra water during times of flooding. Many dams and their associated reservoirs are designed completely or partially to aid in flood protection and control. Many large dams have flood-control reservations in which the level of a reservoir must be kept below a certain elevation before the onset of the rainy/summer melt season to allow

5292-473: The context of natural hazards and disasters , risk management involves "plans, actions, strategies or policies to reduce the likelihood and/or magnitude of adverse potential consequences, based on assessed or perceived risks". Flood control , flood protection , flood defence and flood alleviation are all terms that mean "the detention and/or diversion of water during flood events for the purpose of reducing discharge or downstream inundation". Flood control

5390-568: The damage caused by flooding is to remove buildings from flood-prone areas, leaving them as parks or returning them to wilderness. Floodplain buyout programs have been operated in places like New Jersey (both before and after Hurricane Sandy ), Charlotte , North Carolina, and Missouri . In the United States, FEMA produces flood insurance rate maps that identify areas of future risk, enabling local governments to apply zoning regulations to prevent or minimize property damage. Buildings and other urban infrastructure can be designed so that even if

5488-413: The danger sometimes remain near the shore to satisfy their curiosity or to collect fish from the exposed seabed. A typical wave period for a damaging tsunami is about twelve minutes. Thus, the sea recedes in the drawback phase, with areas well below sea level exposed after three minutes. For the next six minutes, the wave trough builds into a ridge which may flood the coast, and destruction ensues. During

5586-455: The deep ocean has a much larger wavelength of up to 200 kilometres (120 mi). Such a wave travels at well over 800 kilometres per hour (500 mph), but owing to the enormous wavelength the wave oscillation at any given point takes 20 or 30 minutes to complete a cycle and has an amplitude of only about 1 metre (3.3 ft). This makes tsunamis difficult to detect over deep water, where ships are unable to feel their passage. The velocity of

5684-494: The earthquake occurred is where the Pacific Ocean floor is subducting (or being pushed downwards) under Alaska. Examples of tsunamis originating at locations away from convergent boundaries include Storegga about 8,000 years ago, Grand Banks in 1929, and Papua New Guinea in 1998 (Tappin, 2001). The Grand Banks and Papua New Guinea tsunamis came from earthquakes which destabilised sediments, causing them to flow into

5782-408: The earthquake. At the point where its shock has been the most violent the sea is driven back, and suddenly recoiling with redoubled force, causes the inundation. Without an earthquake I do not see how such an accident could happen. The Roman historian Ammianus Marcellinus ( Res Gestae 26.10.15–19) described the typical sequence of a tsunami, including an incipient earthquake, the sudden retreat of

5880-541: The effects of flood waters or high water levels during a flooding event. They include evacuation plans and rescue operations. Flood relief is part of the response and recovery phase in a flood management plan. Floods are caused by many factors or a combination of any of these generally prolonged heavy rainfall (locally concentrated or throughout a catchment area), highly accelerated snowmelt , severe winds over water, unusual high tides, tsunamis , or failure of dams, levees , retention ponds , or other structures that retained

5978-443: The fast recovery of individuals and communities affected, but their use remains limited. Flooding can occur in cities or towns as urban flooding . It can also take place by the sea as coastal flooding . Sea level rise can make coastal flooding worse. In some areas there are also risks of glacial lake outburst floods . There are many adaptation options for flooding: More frequent drenching rains may make it necessary to increase

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6076-406: The flanks and in some cases detachment planes are believed to be developing. However, there is growing controversy about how dangerous these slopes actually are. Other than by landslides or sector collapse , volcanoes may be able to generate waves by pyroclastic flow submergence, caldera collapse, or underwater explosions. Tsunamis have been triggered by a number of volcanic eruptions, including

6174-817: The flow", and deliberately flood some low-lying areas, ideally vegetated, to act as sponges, letting them drain again as the floodwaters go down. Excess water can be used for groundwater replenishment by diversion onto land that can absorb the water. This technique can reduce the impact of later droughts by using the ground as a natural reservoir. It is being used in California, where orchards and vineyards can be flooded without damaging crops, or in other places wilderness areas have been re-engineered to act as floodplains. In many countries, rivers are prone to floods and are often carefully managed. Defenses such as levees, bunds , reservoirs, and weirs are used to prevent rivers from bursting their banks. A weir, also known as

6272-441: The gate. A flood barrier , surge barrier or storm surge barrier is a specific type of floodgate , designed to prevent a storm surge or spring tide from flooding the protected area behind the barrier. A surge barrier is almost always part of a larger flood protection system consisting of floodwalls , levees (also known as dikes), and other constructions and natural geographical features. The self-closing flood barrier (SCFB)

6370-494: The gravitational pull of the moon and sun rather than the displacement of water. Although the meanings of "tidal" include "resembling" or "having the form or character of" tides, use of the term tidal wave is discouraged by geologists and oceanographers. A 1969 episode of the TV crime show Hawaii Five-O entitled "Forty Feet High and It Kills!" used the terms "tsunami" and "tidal wave" interchangeably. The term seismic sea wave

6468-409: The harbour at Halifax , Nova Scotia , Canada . There have been studies of the potential for the use of explosives to induce tsunamis as a tectonic weapon . As early as World War II (1939–1945), consideration of the use of conventional explosives was explored, and New Zealand's military forces initiated Project Seal , which attempted to create small tsunamis with explosives in the area of what

6566-520: The human and socio-economic losses caused by flooding and is part of the larger field of risk management . Flood risk management analyzes the relationships between physical systems and socio-economic environments through flood risk assessment and tries to create understanding and action about the risks posed by flooding. The relationships cover a wide range of topics, from drivers and natural processes, to models and socio-economic consequences. This relationship examines management methods which includes

6664-640: The integration of flood risks and required policies. In flood management, stakeholder engagement is seen as an important way to achieve greater cohesion and consensus. Integrating stakeholder engagement into flood management often provides a more complex analysis of the situation; this generally adds more demand in determining collective solutions and increases the time it takes to determine solutions. Tsunami A tsunami ( /( t ) s uː ˈ n ɑː m i , ( t ) s ʊ ˈ -/ (t)soo- NAH -mee, (t)suu- ; from Japanese : 津波 , lit.   'harbour wave', pronounced [tsɯnami] )

6762-557: The intensity of tsunamis were the Sieberg - Ambraseys scale (1962), used in the Mediterranean Sea and the Imamura-Iida intensity scale (1963), used in the Pacific Ocean. The latter scale was modified by Soloviev (1972), who calculated the tsunami intensity " I " according to the formula: where H a v {\displaystyle {\mathit {H}}_{av}} is the "tsunami height" in metres, averaged along

6860-562: The intensively studied tsunamis in 2004 and 2011, a new 12-point scale was proposed, the Integrated Tsunami Intensity Scale (ITIS-2012), intended to match as closely as possible to the modified ESI2007 and EMS earthquake intensity scales. The first scale that genuinely calculated a magnitude for a tsunami, rather than an intensity at a particular location was the ML scale proposed by Murty & Loomis based on

6958-483: The low barometric pressure of passing tropical cyclones, nor should they be confused with setup, the temporary local raising of sea level caused by strong on-shore winds. Storm surges and setup are also dangerous causes of coastal flooding in severe weather but their dynamics are completely unrelated to tsunami waves. They are unable to propagate beyond their sources, as waves do. The accidental Halifax Explosion in 1917 triggered an 18-metre (59 ft) high tsunami in

7056-422: The main drivers of floods interact with each other. Flood modelling combines factors such as terrain, hydrology , and urban topography to reproduce the evolution of a flood in order to identify the different levels of flooding risks associated with each element exposed. The modelling can be carried out using hydraulic models, conceptual models, or geomorphic methods. Nowadays, there is a growing attention also in

7154-427: The mouth of streams or small rivers, where an estuary begins or where tributary streams, or drainage ditches connect to sloughs . Tide gates close during incoming tides to prevent tidal waters from moving upland, and open during outgoing tides to allow waters to drain out via the culvert and into the estuary side of the dike. The opening and closing of the gates is driven by a difference in water level on either side of

7252-636: The nearest coastline, with the tsunami height defined as the rise of the water level above the normal tidal level at the time of occurrence of the tsunami. This scale, known as the Soloviev-Imamura tsunami intensity scale , is used in the global tsunami catalogues compiled by the NGDC/NOAA and the Novosibirsk Tsunami Laboratory as the main parameter for the size of the tsunami. This formula yields: In 2013, following

7350-405: The next six minutes, the wave changes from a ridge to a trough, and the flood waters recede in a second drawback. Victims and debris may be swept into the ocean. The process repeats with succeeding waves. As with earthquakes, several attempts have been made to set up scales of tsunami intensity or magnitude to allow comparison between different events. The first scales used routinely to measure

7448-856: The ocean and generate a tsunami. They dissipated before travelling transoceanic distances. The cause of the Storegga sediment failure is unknown. Possibilities include an overloading of the sediments, an earthquake or a release of gas hydrates (methane etc.). The 1960 Valdivia earthquake ( M w 9.5), 1964 Alaska earthquake ( M w 9.2), 2004 Indian Ocean earthquake ( M w 9.2), and 2011 Tōhoku earthquake ( M w 9.0) are recent examples of powerful megathrust earthquakes that generated tsunamis (known as teletsunamis ) that can cross entire oceans. Smaller ( M w 4.2) earthquakes in Japan can trigger tsunamis (called local and regional tsunamis) that can devastate stretches of coastline, but can do so in only

7546-437: The ocean, meteorite impacts, and the weather when the atmospheric pressure changes very rapidly—can generate such waves by displacing water. The use of the term tsunami for waves created by landslides entering bodies of water has become internationally widespread in both scientific and popular literature, although such waves are distinct in origin from large waves generated by earthquakes. This distinction sometimes leads to

7644-439: The path of floodwaters. Other solutions, such as HydroSack , are polypropylene exteriors with wood pulp within, though they are one-time use. There are several methods of non-structural flood management that form part of flood risk management strategies. These can involve policies that reduces the amount of urban structures built around floodplains or flood prone areas through land zoning regulations. This helps to reduce

7742-482: The possibility of a meteorite causing a tsunami is debated. Tsunamis can be generated when the sea floor abruptly deforms and vertically displaces the overlying water. Tectonic earthquakes are a particular kind of earthquake that are associated with the Earth's crustal deformation; when these earthquakes occur beneath the sea, the water above the deformed area is displaced from its equilibrium position. More specifically,

7840-433: The potential energy. Difficulties in calculating the potential energy of the tsunami mean that this scale is rarely used. Abe introduced the tsunami magnitude scale M t {\displaystyle {\mathit {M}}_{t}} , calculated from, where h is the maximum tsunami-wave amplitude (in m) measured by a tide gauge at a distance R from the epicentre, a , b and D are constants used to make

7938-539: The production of maps obtained with remote sensing . Flood modelling is helpful for determining building development practices and hazard mitigation methods that reduce the risks associated with flooding. Stakeholder engagement is a useful tool for flood risk management that allows enhanced public engagement for agreements to be reached on policy discussions. Different management considerations can be taken into account including emergency management and disaster risk reduction goals, interactions of land-use planning with

8036-605: The results. Analysis of the effects of shallow and deep underwater explosions indicate that the energy of the explosions does not easily generate the kind of deep, all-ocean waveforms typical of tsunamis because most of the energy creates steam , causes vertical fountains above the water, and creates compressional waveforms. Tsunamis are hallmarked by permanent large vertical displacements of very large volumes of water which do not occur in explosions. Tsunamis are caused by earthquakes, landslides, volcanic explosions, glacier calvings, and bolides . They cause damage by two mechanisms:

8134-572: The risk to people and property is through the production of flood risk maps. Most countries have produced maps which show areas prone to flooding based on flood data. In the UK , the Environment Agency has produced maps which show areas at risk. The map to the right shows a flood map for the City of York , including the floodplain for a 1 in 100-year flood (dark blue), the predicted floodplain for

8232-455: The river spreading over a floodplain) will slow some of the flow more than other parts, spreading the flow over time and blunting the spike. Even slightly blunting the spike significantly decreases the peak flood level. Generally, the higher the peak flood level, the more flood damage is done. Straight, clear, smooth concrete-walled channels speed up flow, and are therefore likely to make flooding downstream worse. Modern flood control seeks to "slow

8330-426: The sea and a following gigantic wave, after the 365 AD tsunami devastated Alexandria . The principal generation mechanism of a tsunami is the displacement of a substantial volume of water or perturbation of the sea. This displacement of water is usually caused by earthquakes, but can also be attributed to landslides, volcanic eruptions, glacier calvings or more rarely by meteorites and nuclear tests. However,

8428-400: The smashing force of a wall of water travelling at high speed, and the destructive power of a large volume of water draining off the land and carrying a large amount of debris with it, even with waves that do not appear to be large. While everyday wind waves have a wavelength (from crest to crest) of about 100 metres (330 ft) and a height of roughly 2 metres (6.6 ft), a tsunami in

8526-432: The spike. Even slightly blunting the spike significantly decreases the peak flood level. Generally, the higher the peak flood level, the more flood damage is done. Modern flood control seeks to "slow the flow", and deliberately flood some low-lying areas, ideally vegetated, to act as sponges, letting them drain again as the floodwaters go down. Where floods interact with housing, industry and farming that flood management

8624-457: The transoceanic reach of significant seismic tsunamis, and 2) that the force that displaces the water is sustained over some length of time such that meteotsunamis cannot be modelled as having been caused instantaneously. In spite of their lower energies, on shorelines where they can be amplified by resonance, they are sometimes powerful enough to cause localised damage and potential for loss of life. They have been documented in many places, including

8722-447: The understanding of the other source mechanisms. Some meteorological conditions, especially rapid changes in barometric pressure, as seen with the passing of a front, can displace bodies of water enough to cause trains of waves with wavelengths. These are comparable to seismic tsunamis, but usually with lower energies. Essentially, they are dynamically equivalent to seismic tsunamis, the only differences being 1) that meteotsunamis lack

8820-457: The use of other terms for landslide-generated waves, including landslide-triggered tsunami , displacement wave , non-seismic wave , impact wave , and, simply, giant wave . While Japan may have the longest recorded history of tsunamis, the sheer destruction caused by the 2004 Indian Ocean earthquake and tsunami event mark it as the most devastating of its kind in modern times, killing around 230,000 people. The Sumatran region

8918-399: The very largest tsunamis, the approaching wave does not break , but rather appears like a fast-moving tidal bore . Open bays and coastlines adjacent to very deep water may shape the tsunami further into a step-like wave with a steep-breaking front. When the tsunami's wave peak reaches the shore, the resulting temporary rise in sea level is termed run up . Run up is measured in metres above

9016-400: The water. Water levels during a flood tend to rise, then fall, very abruptly. The peak flood level occurs as a very steep, short spike; a quick spurt of water. Anything that slows the surface runoff (marshes, meanders, vegetation, porous materials, turbulent flow, the river spreading over a floodplain) will slow some of the flow more than other parts, spreading the flow over time and blunting

9114-461: The water. Flooding can be exacerbated by increased amounts of impervious surface or by other natural hazards such as wildfires, which reduce the supply of vegetation that can absorb rainfall. During times of rain, some of the water is retained in ponds or soil, some is absorbed by grass and vegetation, some evaporates, and the rest travels over the land as surface runoff . Floods occur when ponds, lakes, riverbeds, soil, and vegetation cannot absorb all

9212-636: The winter, part of the channel becomes the Auburn Ice Channel , which has become a local destination for ice climbing. This article about a building or structure in Massachusetts is a stub . You can help Misplaced Pages by expanding it . Flood control Flood management can include flood risk management, which focuses on measures to reduce risk, vulnerability and exposure to flood disasters and providing risk analysis through, for example, flood risk assessment . Flood mitigation

9310-500: The world, due to the absence of public accessibility, technical writing and data, and lack of easy-to-understand information. However, revived attention towards flood mapping has renewed the interest in enhancing current flood mapping for use as a flood risk management method. Flood modelling is a tool used to model flood hazard and the effects on humans and the physical environment. Flood modelling takes into consideration how flood hazards, external and internal processes and factors, and

9408-419: The worst floods in recent U.S. history having cost billions of dollars. Property owners may fit their homes to stop water entering by blocking doors and air vents, waterproofing important areas and sandbagging the edges of the building. Private precautionary measures are increasingly important in flood risk management. Flood mitigation at the property level may also involve preventative measures focused on

9506-576: Was among the deadliest natural disasters in human history, with at least 230,000 people killed or missing in 14 countries bordering the Indian Ocean . The Ancient Greek historian Thucydides suggested in his 5th century BC History of the Peloponnesian War that tsunamis were related to submarine earthquakes , but the understanding of tsunamis remained slim until the 20th century, and much remains unknown. Major areas of current research include determining why some large earthquakes do not generate tsunamis while other smaller ones do. This ongoing research

9604-521: Was confirmed in 1958, when a giant landslide in Lituya Bay , Alaska, caused the highest wave ever recorded, which had a height of 524 metres (1,719 ft). The wave did not travel far as it struck land almost immediately. The wave struck three boats—each with two people aboard—anchored in the bay. One boat rode out the wave, but the wave sank the other two, killing both people aboard one of them. Another landslide-tsunami event occurred in 1963 when

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