Flood

A flood is an overflow of water that submerges land that is usually dry.[1] 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.

Flooding may occur as an overflow of water from water bodies, such as a river, lake, or ocean, in which the water overtops or breaks levees, resulting in some of that water escaping its usual boundaries,[2] or it may occur due to an accumulation of rainwater on saturated ground in an areal flood. While the size of a lake or other body of water will vary with seasonal changes in precipitation and snow melt, these changes in size are unlikely to be considered significant unless they flood property or drown domestic animals.

Floods can also occur in rivers when the flow rate exceeds the capacity of the river channel, particularly at bends or meanders in the waterway. Floods often cause damage to homes and businesses if they are in the natural flood plains of rivers. While riverine flood damage can be eliminated by moving away from rivers and other bodies of water, people have traditionally lived and worked by rivers because the land is usually flat and fertile and because rivers provide easy travel and access to commerce and industry.

Some floods develop slowly, while others such as flash floods can develop in just a few minutes and without visible signs of rain. Additionally, floods can be local, impacting a neighborhood or community, or very large, affecting entire river basins.

Urban flood cropped
Flooding in a street
Erschrecklichewasserfluth
Contemporary picture of the flood that struck the North Sea coast of Germany and Denmark in October 1634.
A Flood on Java 1865-1876 Raden Saleh
People seeking refuge from flood in Jawa Tengah, Java. ca. 1865–1876.
Katrina-new-orleans-flooding3-2005
View of flooded New Orleans in the aftermath of Hurricane Katrina
Venezia-Venice-Venedig-at-night JBU-02
"Regular" flooding in Venice, Italy.
Rapid Creek flooding 1
Flooding of a creek due to heavy monsoonal rain and high tide in Darwin, Northern Territory, Australia.
Jeddah Flood - King Abdullah Street
Jeddah Flood, covering King Abdullah Street in Saudi Arabia.
Flood102405
Flooding near Key West, Florida, United States from Hurricane Wilma's storm surge in October 2005.
Natal Brazil Flood.jpeg
Flooding in a street of Natal, Rio Grande do Norte, Brazil in April 2013.
Minor Flooding in midtown atl
Minor flooding in a parking lot off Juniper street Atlanta on Christmas Eve from thunderstorms caused by an El Nino event. The same El Nino caused recorded highs for January in Atlanta
Trapped woman on a car roof during flash flooding in Toowoomba 2
Flash flooding caused by heavy rain falling in a short amount of time.
BDF0
Dozens of villages were inundated when rain pushed the rivers of northwestern Bangladesh over their banks in early October 2005. The Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA's Terra satellite captured the top image of the flooded Ghaghat and Atrai Rivers on October 12, 2005. The deep blue of the rivers is spread across the countryside in the flood image.

Etymology

The word "flood" comes from the Old English flod, a word common to Germanic languages (compare German Flut, Dutch vloed from the same root as is seen in flow, float; also compare with Latin fluctus, flumen).

Principal types

Areal

Floods can happen on flat or low-lying areas when water is supplied by rainfall or snowmelt more rapidly than it can either infiltrate or run off. The excess accumulates in place, sometimes to hazardous depths. Surface soil can become saturated, which effectively stops infiltration, where the water table is shallow, such as a floodplain, or from intense rain from one or a series of storms. Infiltration also is slow to negligible through frozen ground, rock, concrete, paving, or roofs. Areal flooding begins in flat areas like floodplains and in local depressions not connected to a stream channel, because the velocity of overland flow depends on the surface slope. Endorheic basins may experience areal flooding during periods when precipitation exceeds evaporation.[3]

Riverine (Channel)

Floods occur in all types of river and stream channels, from the smallest ephemeral streams in humid zones to normally-dry channels in arid climates to the world's largest rivers. When overland flow occurs on tilled fields, it can result in a muddy flood where sediments are picked up by run off and carried as suspended matter or bed load. Localized flooding may be caused or exacerbated by drainage obstructions such as landslides, ice, debris, or beaver dams.

Slow-rising floods most commonly occur in large rivers with large catchment areas. The increase in flow may be the result of sustained rainfall, rapid snow melt, monsoons, or tropical cyclones. However, large rivers may have rapid flooding events in areas with dry climate, since they may have large basins but small river channels and rainfall can be very intense in smaller areas of those basins.

Rapid flooding events, including flash floods, more often occur on smaller rivers, rivers with steep valleys, rivers that flow for much of their length over impermeable terrain, or normally-dry channels. The cause may be localized convective precipitation (intense thunderstorms) or sudden release from an upstream impoundment created behind a dam, landslide, or glacier. In one instance, a flash flood killed eight people enjoying the water on a Sunday afternoon at a popular waterfall in a narrow canyon. Without any observed rainfall, the flow rate increased from about 50 to 1,500 cubic feet per second (1.4 to 42 m3/s) in just one minute.[4] Two larger floods occurred at the same site within a week, but no one was at the waterfall on those days. The deadly flood resulted from a thunderstorm over part of the drainage basin, where steep, bare rock slopes are common and the thin soil was already saturated.

Flash floods are the most common flood type in normally-dry channels in arid zones, known as arroyos in the southwest United States and many other names elsewhere. In that setting, the first flood water to arrive is depleted as it wets the sandy stream bed. The leading edge of the flood thus advances more slowly than later and higher flows. As a result, the rising limb of the hydrograph becomes ever quicker as the flood moves downstream, until the flow rate is so great that the depletion by wetting soil becomes insignificant.

Estuarine and coastal

Flooding in estuaries is commonly caused by a combination of sea tidal surges caused by winds and low barometric pressure, and they may be exacerbated by high upstream river flow.

Coastal areas may be flooded by storm events at sea, resulting in waves over-topping defenses or in severe cases by tsunami or tropical cyclones. A storm surge, from either a tropical cyclone or an extratropical cyclone, falls within this category. Research from the NHC (National Hurricane Center) explains: "Storm surge is an abnormal rise of water generated by a storm, over and above the predicted astronomical tides. Storm surge should not be confused with storm tide, which is defined as the water level rise due to the combination of storm surge and the astronomical tide. This rise in water level can cause extreme flooding in coastal areas particularly when storm surge coincides with normal high tide, resulting in storm tides reaching up to 20 feet or more in some cases."[5]

Urban flooding

Urban flooding is the inundation of land or property in a built environment, particularly in more densely populated areas, caused by rainfall overwhelming the capacity of drainage systems, such as storm sewers. Although sometimes triggered by events such as flash flooding or snowmelt, urban flooding is a condition, characterized by its repetitive and systemic impacts on communities, that can happen regardless of whether or not affected communities are located within designated floodplains or near any body of water.[6] Aside from potential overflow of rivers and lakes, snowmelt, stormwater or water released from damaged water mains may accumulate on property and in public rights-of-way, seep through building walls and floors, or backup into buildings through sewer pipes, toilets and sinks.

In urban areas, flood effects can be exacerbated by existing paved streets and roads, which increase the speed of flowing water.

The flood flow in urbanized areas constitutes a hazard to both the population and infrastructure. Some recent catastrophes include the inundations of Nîmes (France) in 1998 and Vaison-la-Romaine (France) in 1992, the flooding of New Orleans (USA) in 2005, and the flooding in Rockhampton, Bundaberg, Brisbane during the 2010–2011 summer in Queensland (Australia). Flood flows in urban environments have been studied relatively recently despite many centuries of flood events.[7] Some recent research has considered the criteria for safe evacuation of individuals in flooded areas.[8]

Catastrophic

Catastrophic riverine flooding is usually associated with major infrastructure failures such as the collapse of a dam, but they may also be caused by drainage channel modification from a landslide, earthquake or volcanic eruption. Examples include outburst floods and lahars. Tsunamis can cause catastrophic coastal flooding, most commonly resulting from undersea earthquakes.

Causes

Upslope factors

The amount, location, and timing of water reaching a drainage channel from natural precipitation and controlled or uncontrolled reservoir releases determines the flow at downstream locations. Some precipitation evaporates, some slowly percolates through soil, some may be temporarily sequestered as snow or ice, and some may produce rapid runoff from surfaces including rock, pavement, roofs, and saturated or frozen ground. The fraction of incident precipitation promptly reaching a drainage channel has been observed from nil for light rain on dry, level ground to as high as 170 percent for warm rain on accumulated snow.[9]

Most precipitation records are based on a measured depth of water received within a fixed time interval. Frequency of a precipitation threshold of interest may be determined from the number of measurements exceeding that threshold value within the total time period for which observations are available. Individual data points are converted to intensity by dividing each measured depth by the period of time between observations. This intensity will be less than the actual peak intensity if the duration of the rainfall event was less than the fixed time interval for which measurements are reported. Convective precipitation events (thunderstorms) tend to produce shorter duration storm events than orographic precipitation. Duration, intensity, and frequency of rainfall events are important to flood prediction. Short duration precipitation is more significant to flooding within small drainage basins.[10]

The most important upslope factor in determining flood magnitude is the land area of the watershed upstream of the area of interest. Rainfall intensity is the second most important factor for watersheds of less than approximately 30 square miles or 80 square kilometres. The main channel slope is the second most important factor for larger watersheds. Channel slope and rainfall intensity become the third most important factors for small and large watersheds, respectively.[11]

Time of Concentration is the time required for runoff from the most distant point of the upstream drainage area to reach the point of the drainage channel controlling flooding of the area of interest. The time of concentration defines the critical duration of peak rainfall for the area of interest.[12] The critical duration of intense rainfall might be only a few minutes for roof and parking lot drainage structures, while cumulative rainfall over several days would be critical for river basins.

Downslope factors

Water flowing downhill ultimately encounters downstream conditions slowing movement. The final limitation in coastal flooding lands is often the ocean or some coastal flooding bars which form natural lakes. In flooding low lands, elevation changes such as tidal fluctuations are significant determinants of coastal and estuarine flooding. Less predictable events like tsunamis and storm surges may also cause elevation changes in large bodies of water. Elevation of flowing water is controlled by the geometry of the flow channel and, especially, by depth of channel, speed of flow and amount of sediments in it [11] Flow channel restrictions like bridges and canyons tend to control water elevation above the restriction. The actual control point for any given reach of the drainage may change with changing water elevation, so a closer point may control for lower water levels until a more distant point controls at higher water levels.

Effective flood channel geometry may be changed by growth of vegetation, accumulation of ice or debris, or construction of bridges, buildings, or levees within the flood channel.

Coincidence

Extreme flood events often result from coincidence such as unusually intense, warm rainfall melting heavy snow pack, producing channel obstructions from floating ice, and releasing small impoundments like beaver dams.[13] Coincident events may cause extensive flooding to be more frequent than anticipated from simplistic statistical prediction models considering only precipitation runoff flowing within unobstructed drainage channels.[14] Debris modification of channel geometry is common when heavy flows move uprooted woody vegetation and flood-damaged structures and vehicles, including boats and railway equipment. Recent field measurements during the 2010–11 Queensland floods showed that any criterion solely based upon the flow velocity, water depth or specific momentum cannot account for the hazards caused by velocity and water depth fluctuations.[7] These considerations ignore further the risks associated with large debris entrained by the flow motion.[8]

Some researchers have mentioned the storage effect in urban areas with transportation corridors created by cut and fill. Culverted fills may be converted to impoundments if the culverts become blocked by debris, and flow may be diverted along streets. Several studies have looked into the flow patterns and redistribution in streets during storm events and the implication on flood modelling.[15]

Effects

Primary effects

The primary effects of flooding include loss of life and damage to buildings and other structures, including bridges, sewerage systems, roadways, and canals.

Floods also frequently damage power transmission and sometimes power generation, which then has knock-on effects caused by the loss of power. This includes loss of drinking water treatment and water supply, which may result in loss of drinking water or severe water contamination. It may also cause the loss of sewage disposal facilities. Lack of clean water combined with human sewage in the flood waters raises the risk of waterborne diseases, which can include typhoid, giardia, cryptosporidium, cholera and many other diseases depending upon the location of the flood.

Damage to roads and transport infrastructure may make it difficult to mobilize aid to those affected or to provide emergency health treatment.

Flood waters typically inundate farm land, making the land unworkable and preventing crops from being planted or harvested, which can lead to shortages of food both for humans and farm animals. Entire harvests for a country can be lost in extreme flood circumstances. Some tree species may not survive prolonged flooding of their root systems.[16]

Secondary and long-term effects

Economic hardship due to a temporary decline in tourism, rebuilding costs, or food shortages leading to price increases is a common after-effect of severe flooding. The impact on those affected may cause psychological damage to those affected, in particular where deaths, serious injuries and loss of property occur.

Urban flooding can cause chronically wet houses, leading to the growth of indoor mold and resulting in adverse health effects, particularly respiratory symptoms.[17] Urban flooding also has significant economic implications for affected neighborhoods. In the United States, industry experts estimate that wet basements can lower property values by 10–25 percent and are cited among the top reasons for not purchasing a home.[18] According to the U.S. Federal Emergency Management Agency (FEMA), almost 40 percent of small businesses never reopen their doors following a flooding disaster.[19] In the United States, insurance is available against flood damage to both homes and businesses.[20]

Benefits

Floods (in particular more frequent or smaller floods) can also bring many benefits, such as recharging ground water, making soil more fertile and increasing nutrients in some soils. Flood waters provide much needed water resources in arid and semi-arid regions where precipitation can be very unevenly distributed throughout the year and kills pests in the farming land. Freshwater floods particularly play an important role in maintaining ecosystems in river corridors and are a key factor in maintaining floodplain biodiversity.[21] Flooding can spread nutrients to lakes and rivers, which can lead to increased biomass and improved fisheries for a few years.

For some fish species, an inundated floodplain may form a highly suitable location for spawning with few predators and enhanced levels of nutrients or food.[22] Fish, such as the weather fish, make use of floods in order to reach new habitats. Bird populations may also profit from the boost in food production caused by flooding.[23]

Periodic flooding was essential to the well-being of ancient communities along the Tigris-Euphrates Rivers, the Nile River, the Indus River, the Ganges and the Yellow River among others. The viability of hydropower, a renewable source of energy, is also higher in flood prone regions.

Flood safety planning

Greeley, CO, September 19, 2013 (12441526333)
Aftermath of flooding in Colorado, 2013

At the most basic level, the best defense against floods is to seek higher ground for high-value uses while balancing the foreseeable risks with the benefits of occupying flood hazard zones.[24]:22–23 Critical community-safety facilities, such as hospitals, emergency-operations centers, and police, fire, and rescue services, should be built in areas least at risk of flooding. Structures, such as bridges, that must unavoidably be in flood hazard areas should be designed to withstand flooding. Areas most at risk for flooding could be put to valuable uses that could be abandoned temporarily as people retreat to safer areas when a flood is imminent.

Planning for flood safety involves many aspects of analysis and engineering, including:

  • observation of previous and present flood heights and inundated areas,
  • statistical, hydrologic, and hydraulic model analyses,
  • mapping inundated areas and flood heights for future flood scenarios,
  • long-term land use planning and regulation,
  • engineering design and construction of structures to control or withstand flooding,
  • intermediate-term monitoring, forecasting, and emergency-response planning, and
  • short-term monitoring, warning, and response operations.

Each topic presents distinct yet related questions with varying scope and scale in time, space, and the people involved. Attempts to understand and manage the mechanisms at work in floodplains have been made for at least six millennia.[25]

In the United States, the Association of State Floodplain Managers works to promote education, policies, and activities that mitigate current and future losses, costs, and human suffering caused by flooding and to protect the natural and beneficial functions of floodplains – all without causing adverse impacts.[26] A portfolio of best practice examples for disaster mitigation in the United States is available from the Federal Emergency Management Agency.[27]

Control

In many countries around the world, waterways prone to floods are often carefully managed. Defenses such as detention basins, levees,[28] bunds, reservoirs, and weirs are used to prevent waterways from overflowing their banks. When these defenses fail, emergency measures such as sandbags or portable inflatable tubes are often used to try to stem flooding. Coastal flooding has been addressed in portions of Europe and the Americas with coastal defenses, such as sea walls, beach nourishment, and barrier islands.

In the riparian zone near rivers and streams, erosion control measures can be taken to try to slow down or reverse the natural forces that cause many waterways to meander over long periods of time. Flood controls, such as dams, can be built and maintained over time to try to reduce the occurrence and severity of floods as well. In the United States, the U.S. Army Corps of Engineers maintains a network of such flood control dams.

In areas prone to urban flooding, one solution is the repair and expansion of man-made sewer systems and stormwater infrastructure. Another strategy is to reduce impervious surfaces in streets, parking lots and buildings through natural drainage channels, porous paving, and wetlands (collectively known as green infrastructure or sustainable urban drainage systems (SUDS)). Areas identified as flood-prone can be converted into parks and playgrounds that can tolerate occasional flooding. Ordinances can be adopted to require developers to retain stormwater on site and require buildings to be elevated, protected by floodwalls and levees, or designed to withstand temporary inundation. Property owners can also invest in solutions themselves, such as re-landscaping their property to take the flow of water away from their building and installing rain barrels, sump pumps, and check valves.

Analysis of flood information

A series of annual maximum flow rates in a stream reach can be analyzed statistically to estimate the 100-year flood and floods of other recurrence intervals there. Similar estimates from many sites in a hydrologically similar region can be related to measurable characteristics of each drainage basin to allow indirect estimation of flood recurrence intervals for stream reaches without sufficient data for direct analysis.

Physical process models of channel reaches are generally well understood and will calculate the depth and area of inundation for given channel conditions and a specified flow rate, such as for use in floodplain mapping and flood insurance. Conversely, given the observed inundation area of a recent flood and the channel conditions, a model can calculate the flow rate. Applied to various potential channel configurations and flow rates, a reach model can contribute to selecting an optimum design for a modified channel. Various reach models are available as of 2015, either 1D models (flood levels measured in the channel) or 2D models (variable flood depths measured across the extent of a floodplain). HEC-RAS,[29] the Hydraulic Engineering Center model, is among the most popular software, if only because it is available free of charge. Other models such as TUFLOW[30] combine 1D and 2D components to derive flood depths across both river channels and the entire floodplain.

Physical process models of complete drainage basins are even more complex. Although many processes are well understood at a point or for a small area, others are poorly understood at all scales, and process interactions under normal or extreme climatic conditions may be unknown. Basin models typically combine land-surface process components (to estimate how much rainfall or snowmelt reaches a channel) with a series of reach models. For example, a basin model can calculate the runoff hydrograph that might result from a 100-year storm, although the recurrence interval of a storm is rarely equal to that of the associated flood. Basin models are commonly used in flood forecasting and warning, as well as in analysis of the effects of land use change and climate change.

Flood forecasting

Anticipating floods before they occur allows for precautions to be taken and people to be warned [31] so that they can be prepared in advance for flooding conditions. For example, farmers can remove animals from low-lying areas and utility services can put in place emergency provisions to re-route services if needed. Emergency services can also make provisions to have enough resources available ahead of time to respond to emergencies as they occur. People can evacuate areas to be flooded.

In order to make the most accurate flood forecasts for waterways, it is best to have a long time-series of historical data that relates stream flows to measured past rainfall events.[32] Coupling this historical information with real-time knowledge about volumetric capacity in catchment areas, such as spare capacity in reservoirs, ground-water levels, and the degree of saturation of area aquifers is also needed in order to make the most acrate flood forecasts.

Radar estimates of rainfall and general weather forecasting techniques are also important components of good flood forecasting. In areas where good quality data is available, the intensity and height of a flood can be predicted with fairly good accuracy and plenty of lead time. The output of a flood forecast is typically a maximum expected water level and the likely time of its arrival at key locations along a waterway,[33] and it also may allow for the computation of the likely statistical return period of a flood. In many developed countries, urban areas at risk of flooding are protected against a 100-year flood – that is a flood that has a probability of around 63% of occurring in any 100-year period of time.

According to the U.S. National Weather Service (NWS) Northeast River Forecast Center (RFC) in Taunton, Massachusetts, a rule of thumb for flood forecasting in urban areas is that it takes at least 1 inch (25 mm) of rainfall in around an hour's time in order to start significant ponding of water on impermeable surfaces. Many NWS RFCs routinely issue Flash Flood Guidance and Headwater Guidance, which indicate the general amount of rainfall that would need to fall in a short period of time in order to cause flash flooding or flooding on larger water basins.[34]

In the United States, an integrated approach to real-time hydrologic computer modelling utilizes observed data from the U.S. Geological Survey (USGS),[35] various cooperative observing networks,[36] various automated weather sensors, the NOAA National Operational Hydrologic Remote Sensing Center (NOHRSC),[37] various hydroelectric companies, etc. combined with quantitative precipitation forecasts (QPF) of expected rainfall and/or snow melt to generate daily or as-needed hydrologic forecasts.[33] The NWS also cooperates with Environment Canada on hydrologic forecasts that affect both the USA and Canada, like in the area of the Saint Lawrence Seaway.

The Global Flood Monitoring System, "GFMS," a computer tool which maps flood conditions worldwide, is available online. Users anywhere in the world can use GFMS to determine when floods may occur in their area. GFMS uses precipitation data from NASA's Earth observing satellites and the Global Precipitation Measurement satellite, "GPM." Rainfall data from GPM is combined with a land surface model that incorporates vegetation cover, soil type, and terrain to determine how much water is soaking into the ground, and how much water is flowing into streamflow.

Users can view statistics for rainfall, streamflow, water depth, and flooding every 3 hours, at each 12 kilometer gridpoint on a global map. Forecasts for these parameters are 5 days into the future. Users can zoom in to see inundation maps (areas estimated to be covered with water) in 1 kilometer resolution.[38][39]

Deadliest floods

Below is a list of the deadliest floods worldwide, showing events with death tolls at or above 100,000 individuals.

Death toll Event Location Date
2,500,000–3,700,000[40] 1931 China floods China 1931
900,000–2,000,000 1887 Yellow River flood China 1887
500,000–700,000 1938 Yellow River flood China 1938
231,000 Banqiao Dam failure, result of Typhoon Nina. Approximately 86,000 people died from flooding and another 145,000 died during subsequent disease. China 1975
230,000 2004 Indian Ocean tsunami Indonesia 2004
145,000 1935 Yangtze river flood China 1935
100,000+ St. Felix's flood, storm surge Netherlands 1530
100,000 Hanoi and Red River Delta flood North Vietnam 1971
100,000 1911 Yangtze river flood China 1911

In myth and religion

Flood myths (great, civilization-destroying floods) are widespread in many cultures.

Flood events in the form of divine retribution have also been described in religious texts. As a prime example, the Genesis flood narrative plays a prominent role in Judaism, Christianity and Islam.

See also

References

  1. ^ MSN Encarta Dictionary, Flood, Retrieved on 2006-12-28, Archived on 2009-10-31
  2. ^ Glossary of Meteorology (June 2000) Flood Archived 2007-08-24 at the Wayback Machine, Retrieved on 2009-01-09
  3. ^ Jones, Myrtle (2000). "Ground-water flooding in glacial terrain of southern Puget Sound, Washington". Retrieved 2015-07-23.
  4. ^ Hjalmarson, Hjalmar W. (December 1984). "Flash Flood in Tanque Verde Creek, Tucson, Arizona". Journal of Hydraulic Engineering. 110 (12): 1841–1852. doi:10.1061/(ASCE)0733-9429(1984)110:12(1841).
  5. ^ "Storm Surge Overview". noaa.gov. Retrieved 3 December 2015.
  6. ^ Center for Neighborhood Technology, Chicago IL, "The Prevalence and Cost of Urban Flooding", May 2013
  7. ^ a b Brown, Richard; Chanson, Hubert; McIntosh, Dave; Madhani, Jay (2011). Turbulent Velocity and Suspended Sediment Concentration Measurements in an Urban Environment of the Brisbane River Flood Plain at Gardens Point on 12–13 January 2011. Hydraulic Model Report No. CH83/11. p. 120. ISBN 978-1-74272-027-2.
  8. ^ a b Chanson, H., Brown, R., McIntosh, D. (26 June 2014). "Human body stability in floodwaters: The 2011 flood in Brisbane CBD". In L. Toombes (ed.). Hydraulic structures and society - Engineering challenges and extremes. Brisbane, Australia: Proceedings of the 5th IAHR International Symposium on Hydraulic Structures (ISHS2014). pp. 1–9. doi:10.14264/uql.2014.48. ISBN 978-1-74272-115-6.CS1 maint: Uses authors parameter (link)
  9. ^ Babbitt, Harold E. & Doland, James J., Water Supply Engineering, McGraw-Hill Book Company, 1949
  10. ^ Simon, Andrew L., Basic Hydraulics, John Wiley & Sons, 1981, ISBN 0-471-07965-0
  11. ^ a b Simon, Andrew L., Practical Hydraulics, John Wiley & Sons, 1981, ISBN 0-471-05381-3
  12. ^ Urquhart, Leonard Church, Civil Engineering Handbook, McGraw-Hill Book Company, 1959
  13. ^ Abbett, Robert W., American Civil Engineering Practice, John Wiley & Sons, 1956
  14. ^ United States Department of the Interior, Bureau of Reclamation, Design of Small Dams, United States Government Printing Office, 1973
  15. ^ Werner, MGF; Hunter, NM; Bates, PD (2006). "Identifiability of Distributed Floodplain Roughness Values in Flood Extent Estimation". Journal of Hydrology. 314 (1–4): 139–157. Bibcode:2005JHyd..314..139W. doi:10.1016/j.jhydrol.2005.03.012.
  16. ^ Stephen Bratkovich, Lisa Burban, et al., "Flooding and its Effects on Trees", USDA Forest Service, Northeastern Area State and Private Forestry, St. Paul, MN, September 1993
  17. ^ Indoor Air Quality (IAQ) Scientific Findings Resource Bank (IAQ-SFRB), "Health Risks or Dampness or Mold in Houses" Archived 2013-10-04 at the Wayback Machine
  18. ^ Center for Neighborhood Technology, Chicago IL "The Prevalence and Cost of Urban Flooding", May 2013
  19. ^ "Protecting Your Businesses", last updated March 2013
  20. ^ "National Flood Insurance Program". FloodSmart.gov. Retrieved 2015-07-06.
  21. ^ WMO/GWP Associated Programme on Flood Management, "Environmental Aspects of Integrated Flood Management", 2007
  22. ^ Extension of the Flood Pulse Concept, Retrieved on 2012-06-12
  23. ^ Birdlife soars above Botswana's floodplains Archived 2011-02-09 at the Wayback Machine (2010-10-15), Retrieved on 2012-06-12
  24. ^ Eychaner, J.H. (2015) Lessons from a 500-year record of flood elevations, Association of State Floodplain Managers, Technical Report 7, Accessed 2015-06-27
  25. ^ Dyhouse, G., "Flood modelling Using HEC-RAS (First Edition)", Haestad Press, Waterbury (USA) 2003
  26. ^ "Association of State Floodplain Managers". Retrieved 2015-07-13.
  27. ^ "Best Practices Portfolio". Federal Emergency Management Agency. Retrieved 2015-07-06.
  28. ^ Henry Petroski (2006). Levees and Other Raised Ground. 94. American Scientist. pp. 7–11.
  29. ^ United States Army Corps of Engineers, Davis, CA, Hydrologic Engineering Center
  30. ^ BMT WBM Pty Ltd., Brisbane, Queensland, "TUFLOW Flood and Tide Simulation Software" Archived 2008-06-27 at the Wayback Machine
  31. ^ "Flood Warnings". Environment Agency. 2013-04-30. Retrieved 2013-06-17.
  32. ^ "Australia rainfall and river conditions". Bom.gov.au. Retrieved 2013-06-17.
  33. ^ a b Connelly, Brian A; Braatz, Dean T; Halquist, John B; Deweese, Michael M; Larson, Lee; Ingram, John J (1999). "Advanced Hydrologic Prediction System". Journal of Geophysical Research. 104 (D16): 19, 655. Bibcode:1999JGR...10419655C. doi:10.1029/1999JD900051. Retrieved 4 February 2013.
  34. ^ "FFG". Retrieved 29 January 2013.
  35. ^ "WaterWatch". 4 February 2013. Retrieved 4 February 2013.
  36. ^ "Community Collaborative Rain, Hail and Snow Network". Retrieved 4 February 2013.
  37. ^ "NOHRSC". 2 May 2012. Retrieved 4 February 2013.
  38. ^ "Predicting Floods". science.nasa.gov. Retrieved 2015-07-22.
  39. ^ ScienceCasts: Predicting Floods. YouTube. 21 July 2015. Retrieved 13 January 2016 – via YouTube.
  40. ^ Worst Natural Disasters In History Archived 2008-04-21 at the Wayback Machine (2012-06-07), Retrieved on 2012-06-12

Bibliography

External links

Denial of Service attack

In computing, a denial-of-service attack (DoS attack) is a cyber-attack in which the perpetrator seeks to make a machine or network resource unavailable to its intended users by temporarily or indefinitely disrupting services of a host connected to the Internet. Denial of service is typically accomplished by flooding the targeted machine or resource with superfluous requests in an attempt to overload systems and prevent some or all legitimate requests from being fulfilled.In a distributed denial-of-service attack (DDoS attack), the incoming traffic flooding the victim originates from many different sources. This effectively makes it impossible to stop the attack simply by blocking a single source.

A DoS or DDoS attack is analogous to a group of people crowding the entry door of a shop, making it hard for legitimate customers to enter, disrupting trade.

Criminal perpetrators of DoS attacks often target sites or services hosted on high-profile web servers such as banks or credit card payment gateways. Revenge, blackmail and activism can motivate these attacks.

Flash flood

A flash flood is a rapid flooding of low-lying areas: washes, rivers, dry lakes and basins. It may be caused by heavy rain associated with a severe thunderstorm, hurricane, tropical storm, or meltwater from ice or snow flowing over ice sheets or snowfields. Flash floods may occur after the collapse of a natural ice or debris dam, or a human structure such as a man-made dam, as occurred before the Johnstown Flood of 1889. Flash floods are distinguished from regular floods by having a timescale of fewer than six hours between rainfall and the onset of flooding. The water that is temporarily available is often used by plants with rapid germination and short growth cycles and by specially adapted animal life.

Flood (Halo)

The Flood is a fictional parasitic alien life form in the Halo multimedia franchise. It is introduced in the 2001 video game Halo: Combat Evolved, and returns in later entries in the series such as Halo 2, Halo 3, and Halo Wars. The Flood infects any sentient life of sufficient size. The Flood-infected creatures, also called Flood, in turn infect other hosts. The parasite is depicted as such a threat that the ancient Forerunners killed themselves and all other sentient life in the galaxy in an effort to stop the Flood's spread.

The Flood's design and fiction was spearheaded by Bungie artist Robert McLees, who utilized unused concepts from the earlier Bungie game Marathon 2. The setting of the first game, the ringworld Halo, was stripped of many of its large creatures to make the Flood's surprise appearance more startling. Bungie environment artist Vic DeLeon spent six months of pre-production time refining the Flood's fleshy aesthetic and designing the organic interiors of Flood-infested space ships for Halo 3.

The player's discovery of the Flood in Halo: Combat Evolved is a major plot twist, and was one of the surprises reviewers noted positively upon release. The Flood's return in Halo 2 and Halo 3 was less enthusiastically praised. Reaction to the Flood has varied. While some found the Flood too derivative and a cliché element of science fiction, some others ranked it among the greatest video game villains of all time.

Flood control

Flood control methods are used to reduce or prevent the detrimental effects of flood waters. Flood relief methods are used to reduce the effects of flood waters or high water levels.

Flood myth

A flood myth or deluge myth is a narrative in which a great flood, usually sent by a deity or deities, destroys civilization, often in an act of divine retribution. Parallels are often drawn between the flood waters of these myths and the primaeval waters found in certain creation myths, as the flood waters are described as a measure for the cleansing of humanity, in preparation for rebirth. Most flood myths also contain a culture hero, who "represents the human craving for life".The flood myth motif is found among many cultures as seen in the Mesopotamian flood stories, Deucalion and Pyrrha in Greek mythology, the Genesis flood narrative, Pralaya in Hinduism, the Gun-Yu in Chinese mythology, Bergelmir in Norse mythology, in the lore of the K'iche' and Maya peoples in Mesoamerica, the Lac Courte Oreilles Ojibwa tribe of Native Americans in North America, the Muisca, and Cañari Confederation, in South America, Africa, and the Aboriginal tribes in southern Australia.

Floodplain

A floodplain or flood plain is an area of land adjacent to a stream or river which stretches from the banks of its channel to the base of the enclosing valley walls, and which experiences flooding during periods of high discharge. The soils usually consist of levees, silts, and sands deposited during floods. Levees are the heaviest materials (usually pebble-size) and they are deposited first; silts and sands are finer materials.

Genesis flood narrative

The Genesis flood narrative is a flood myth found in the Tanakh (chapters 6–9 in the Book of Genesis). The story tells of God's decision to return the Earth to its pre-creation state of watery chaos and then remake it in a reversal of creation. The narrative has very strong similarities to parts of the Epic of Gilgamesh which predates the Book of Genesis.

A global flood as described in this myth is inconsistent with the physical findings of geology and paleontology. A branch of creationism known as flood geology is a pseudoscientific attempt to argue that such a global flood actually occurred.

Great Mississippi Flood of 1927

The Great Mississippi Flood of 1927 was the most destructive river flood in the history of the United States, with 27,000 square miles (70,000 km2) inundated up to a depth of 30 feet (9 m). To try to prevent future floods, the federal government built the world's longest system of levees and floodways.

Ninety-four percent of the more than 630,000 people affected by the flood lived in the states of Arkansas, Mississippi, and Louisiana, most in the Mississippi Delta. More than 200,000 African Americans were displaced from their homes along the Lower Mississippi River and had to live for lengthy periods in relief camps. As a result of this disruption, many joined the Great Migration from the south to northern and midwestern industrial cities rather than return to rural agricultural labor. This massive population movement increased from World War II until 1970.

Great Molasses Flood

The Great Molasses Flood, also known as the Boston Molasses Disaster or the Great Boston Molasses Flood, and sometimes referred to locally as the Boston Molassacre, occurred on January 15, 1919 in the North End neighborhood of Boston, Massachusetts. A large storage tank burst, filled with 2,300,000 US gal (8,700 m3)(8,706,447 liters) (ca 12,000 tons; 10,886 metric tons; 24,000,000 lbs ) of molasses, and a wave of molasses rushed through the streets at an estimated 35 mph (56 km/h), killing 21 and injuring 150. The event entered local folklore and residents claimed for decades afterwards that the area still smelled of molasses on hot summer days.

Levee

A levee (), dike, dyke, embankment, floodbank or stopbank is an elongated naturally occurring ridge or artificially constructed fill or wall, which regulates water levels. It is usually earthen and often parallel to the course of a river in its floodplain or along low-lying coastlines.

List of floods

This is a list of major floods.

Long Island

Long Island is a densely populated island off the East Coast of the United States, beginning at New York Harbor approximately 0.35 miles (0.56 km) from Manhattan Island and extending eastward into the Atlantic Ocean. The island comprises four counties in the U.S. state of New York. Kings and Queens Counties (the New York City boroughs of Brooklyn and Queens, respectively) and Nassau County share the western third of the island, while Suffolk County occupies the eastern two-thirds. More than half of New York City's residents now live on Long Island, in Brooklyn and Queens. However, many people in the New York metropolitan area (including those in Brooklyn and Queens) colloquially use the term Long Island (or the Island) to refer exclusively to Nassau and Suffolk Counties, which are mainly suburban in character, conversely employing the term the City to mean Manhattan alone.Broadly speaking, "Long Island" may refer both to the main island and the surrounding outer barrier islands. North of the island is Long Island Sound, across which lie Westchester County, New York, and the state of Connecticut. Across the Block Island Sound to the northeast is the state of Rhode Island. To the west, Long Island is separated from the Bronx and the island of Manhattan by the East River. To the extreme southwest, it is separated from Staten Island and the state of New Jersey by Upper New York Bay, the Narrows, and Lower New York Bay. To the east lie Block Island—which belongs to the State of Rhode Island—and numerous smaller islands.

Both the longest and the largest island in the contiguous United States, Long Island extends 118 miles (190 km) eastward from New York Harbor to Montauk Point, with a maximum north-to-south distance of 23 miles (37 km) between Long Island Sound and the Atlantic coast. With a land area of 1,401 square miles (3,630 km2), Long Island is the 11th-largest island in the United States and the 149th-largest island in the world—larger than the 1,214 square miles (3,140 km2) of the smallest U.S. state, Rhode Island.With a Census-estimated population of 7,869,820 in 2017, constituting nearly 40% of New York State's population, Long Island is the most populated island in any U.S. state or territory, and the 18th-most populous island in the world (ahead of Ireland, Jamaica, and Hokkaidō). Its population density is 5,595.1 inhabitants per square mile (2,160.3/km2). If Long Island geographically constituted an independent metropolitan statistical area, it would rank fourth most populous in the United States; while if it were a U.S. state, Long Island would rank 13th in population and first in population density. Long Island is culturally and ethnically diverse, featuring some of the wealthiest and most expensive neighborhoods in the Western Hemisphere near the shorelines as well as working-class areas in all four counties.

As a hub of commercial aviation, Long Island contains two of the New York City metropolitan area's three busiest airports, JFK International Airport and LaGuardia Airport, in addition to Islip MacArthur Airport; as well as two major air traffic control radar facilities, the New York TRACON and the New York ARTCC. Nine bridges and 13 tunnels (including railroad tunnels) connect Brooklyn and Queens to the three other boroughs of New York City. Ferries connect Suffolk County northward across Long Island Sound to the state of Connecticut. The Long Island Rail Road is the busiest commuter railroad in North America and operates 24/7. Nassau County high school students often feature prominently as winners of the Intel International Science and Engineering Fair and similar STEM-based academic awards. Biotechnology companies and scientific research play a significant role in Long Island's economy, including research facilities at Brookhaven National Laboratory, Cold Spring Harbor Laboratory, Plum Island Animal Disease Center, State University of New York at Stony Brook, the New York University Tandon School of Engineering, the City University of New York, and Hofstra Northwell School of Medicine.

Noah

In Abrahamic religions, Noah ( NOH-ə) was the tenth and last of the pre-Flood Patriarchs. The story of Noah's Ark is told in the Bible's Genesis flood narrative. The biblical account is followed by the story of the Curse of Ham.

In addition to the Book of Genesis, Noah is mentioned in the Old Testament in the First Book of Chronicles, and the books of Tobit, Wisdom, Sirach, Isaiah, Ezekiel, 2 Esdras, 4 Maccabees; in the New Testament, he is mentioned in the gospels of Matthew, and Luke, the Epistle to the Hebrews, 1st Peter and 2nd Peter. Noah was the subject of much elaboration in the literature of later Abrahamic religions, including the Quran (Surahs 71, 7, 1, and 21).

Noah's Ark

Noah's Ark (Hebrew: תיבת נח‎; Biblical Hebrew: Tevat Noaḥ) is the vessel in the Genesis flood narrative (Genesis chapters 6–9) through which God spares Noah, his family, and examples of all the world's animals from a world-engulfing flood. The story in Genesis is repeated, with variations, in the Quran, where the ark appears as Safina Nūḥ (Arabic: سفينة نوح‎ "Noah's boat").

Searches for Noah's Ark have been made from at least the time of Eusebius (c. 275–339 CE), and believers in the Ark continue to search for it in modern times. Many searches have been mounted for the ark, but no confirmable physical proof of the ark has ever been found. There is no scientific evidence that Noah's Ark existed as it is described in the Bible, nor is there evidence in the geologic record for the biblical global flood.

North Sea flood of 1953

The 1953 North Sea flood was a major flood caused by a heavy storm that occurred on the night of Saturday, 31 January 1953 and morning of Sunday, 1 February 1953. The floods struck the Netherlands, Belgium, England and Scotland.

A combination of a high spring tide and a severe European windstorm over the North Sea caused a storm tide; the combination of wind, high tide, and low pressure led to a water level of more than 5.6 metres (18.4 ft) above mean sea level in some locations. The flood and waves overwhelmed sea defences and caused extensive flooding. The Netherlands, a country with 20% of its territory below mean sea level and 50% less than 1 metre (3.3 ft) above sea level and which relies heavily on sea defences, was worst affected, recording 1,836 deaths and widespread property damage. Most of the casualties occurred in the southern province of Zeeland. In England, 307 people were killed in the counties of Lincolnshire, Norfolk, Suffolk and Essex. Nineteen were killed in Scotland. Twenty-eight people were killed in West Flanders, Belgium.

In addition, more than 230 deaths occurred on water craft along Northern European coasts as well as on ships in deeper waters of the North Sea. The ferry MV Princess Victoria was lost at sea in the North Channel east of Belfast with 133 fatalities, and many fishing trawlers sank.

Realising that such infrequent events could recur, the Netherlands, particularly, and the United Kingdom carried out major studies on strengthening of coastal defences. The Netherlands developed the Delta Works, an extensive system of dams and storm surge barriers. The UK constructed storm surge barriers on the River Thames below London and on the River Hull where it meets the Humber Estuary.

Red River of the North

The Red River (French: Rivière rouge or Rivière Rouge du Nord, American English: Red River of the North) is a North American river. Originating at the confluence of the Bois de Sioux and Otter Tail rivers between the U.S. states of Minnesota and North Dakota, it flows northward through the Red River Valley, forming most of the border of Minnesota and North Dakota and continuing into Manitoba. It empties into Lake Winnipeg, whose waters join the Nelson River and ultimately flow into Hudson Bay.

Several urban areas have developed on both sides of the Red River, including those of Fargo-Moorhead and Grand Forks-East Grand Forks in states of North Dakota and Minnesota, respectively, in the United States and Winnipeg in Canada. The Red is about 885 kilometres (550 mi) long, of which about 635 kilometres (395 mi) are in the United States and about 255 kilometres (158 mi) are in Canada. The river falls 70 metres (230 ft) on its trip to Lake Winnipeg, where it spreads into the vast deltaic wetland known as Netley Marsh.

In the United States, the Red River is sometimes called the Red River of the North. This distinguishes it from the so-called Red River of the South, a tributary of the Atchafalaya River that forms part of the border between Texas, Oklahoma, and Arkansas.

Long a highway for trade, the Red has been designated as a Canadian Heritage River.

Spillway

A spillway is a structure used to provide the controlled release of flows from a dam or levee into a downstream area, typically the riverbed of the dammed river itself. In the United Kingdom, they may be known as overflow channels. Spillways ensure that the water does not overflow and damage or destroy the dam.

Floodgates and fuse plugs may be designed into spillways to regulate water flow and reservoir level. Such a spillway can be used to regulate downstream flows – by releasing water in small amounts before the reservoir is full, operators can prevent sudden large releases that would happen if the dam were overtopped.

Other uses of the term "spillway" include bypasses of dams or outlets of channels used during high water, and outlet channels carved through natural dams such as moraines.

Water normally flows over a spillway only during flood periods – when the reservoir cannot hold the excess of water entering the reservoir over the amount used. In contrast, an intake tower is a structure used to release water on a regular basis for water supply, hydroelectricity generation, etc.

Yangtze

The Yangtze or Yangzi (English: or ), which is 6,300 km (3,915 mi) long, is the longest river in Asia, the third-longest in the world and the longest in the world to flow entirely within one country. Its source is in the northern part of the Tibetan Plateau and it flows 6,300 km (3,900 mi) in a generally eastern direction to the East China Sea. It is the sixth-largest river by discharge volume in the world. Its drainage basin comprises one-fifth of the land area of China, and is home to nearly one-third of the country's population.The Yangtze has played a major role in the history, culture and economy of China. For thousands of years, the river has been used for water, irrigation, sanitation, transportation, industry, boundary-marking and war. The prosperous Yangtze River Delta generates as much as 20% of the PRC's GDP. The Three Gorges Dam on the Yangtze is the largest hydro-electric power station in the world. In mid-2014, the Chinese government announced it was building a multi-tier transport network, comprising railways, roads and airports, to create a new economic belt alongside the river.The Yangtze flows through a wide array of ecosystems and is habitat to several endemic and endangered species including the Chinese alligator, the narrow-ridged finless porpoise, the Chinese paddlefish, the (extinct) Yangtze River dolphin or baiji, and the Yangtze sturgeon. In recent years, the river has suffered from industrial pollution, plastic pollution, agricultural run-off, siltation, and loss of wetland and lakes, which exacerbates seasonal flooding. Some sections of the river are now protected as nature reserves. A stretch of the upstream Yangtze flowing through deep gorges in western Yunnan is part of the Three Parallel Rivers of Yunnan Protected Areas, a UNESCO World Heritage Site.

Yellow River

The Yellow River or Huang He (listen ) is the second longest river in China, after the Yangtze River, and the sixth longest river system in the world at the estimated length of 5,464 km (3,395 mi). Originating in the Bayan Har Mountains in Qinghai province of Western China, it flows through nine provinces, and it empties into the Bohai Sea near the city of Dongying in Shandong province. The Yellow River basin has an east–west extent of about 1,900 kilometers (1,180 mi) and a north–south extent of about 1,100 km (680 mi). Its total drainage area is about 752,546 square kilometers (290,560 sq mi).

Its basin was the birthplace of ancient Chinese civilization, and it was the most prosperous region in early Chinese history. There are frequent devastating floods and course changes produced by the continual elevation of the river bed, sometimes above the level of its surrounding farm fields.

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