A pandemic is an epidemic of disease that has spread across a large region. This may include noncommunicable diseases. A widespread endemic disease, stable in terms of how many people are getting sick from it is not a pandemic. Further, flu pandemics exclude recurrences of seasonal flu. Throughout history, there have been a number such as smallpox and tuberculosis. One of the most devastating pandemics was the Black Death, which killed over 75 million people in 1350; the most recent pandemics include the HIV pandemic as well as the 2009 H1N1 pandemics. A pandemic is an epidemic occurring on a scale which crosses international boundaries affecting a large number of people. Pandemics can occur in important agricultural organisms or in other organisms; the World Health Organization has a six-stage classification that describes the process by which a novel influenza virus moves from the first few infections in humans through to a pandemic. This starts with the virus infecting animals, with a few cases where animals infect people moves through the stage where the virus begins to spread directly between people, ends with a pandemic when infections from the new virus have spread worldwide and it will be out of control until we stop it.
A disease or condition is not a pandemic because it is widespread or kills many people. For instance, cancer is responsible for many deaths but is not considered a pandemic because the disease is not infectious or contagious. In a virtual press conference in May 2009 on the influenza pandemic, Dr Keiji Fukuda, Assistant Director-General ad interim for Health Security and Environment, WHO said "An easy way to think about pandemic … is to say: a pandemic is a global outbreak. You might ask yourself:'What is a global outbreak'? Global outbreak means that we see both spread of the agent … and we see disease activities in addition to the spread of the virus."In planning for a possible influenza pandemic, the WHO published a document on pandemic preparedness guidance in 1999, revised in 2005 and in February 2009, defining phases and appropriate actions for each phase in an aide memoir entitled WHO pandemic phase descriptions and main actions by phase. The 2009 revision, including definitions of a pandemic and the phases leading to its declaration, were finalized in February 2009.
The pandemic H1N1 2009 virus mentioned in the document. All versions of this document refer to influenza; the phases are defined by the spread of the disease. HIV originated in Africa, spread to the United States via Haiti between 1966 and 1972. AIDS is a pandemic, with infection rates as high as 25% in southern and eastern Africa. In 2006, the HIV prevalence rate among pregnant women in South Africa was 29.1%. Effective education about safer sexual practices and bloodborne infection precautions training have helped to slow down infection rates in several African countries sponsoring national education programs. Infection rates are rising again in Asia and the Americas; the AIDS death toll in Africa may reach 90–100 million by 2025. There have been a number of significant pandemics recorded in human history zoonoses which came about with the domestication of animals, such as influenza and tuberculosis. There have been a number of significant epidemics that deserve mention above the "mere" destruction of cities: Plague of Athens, 430 BC.
Typhoid fever killed a quarter of the Athenian troops, a quarter of the population over four years. This disease fatally weakened the dominance of Athens, but the sheer virulence of the disease prevented its wider spread; the exact cause of the plague was unknown for many years. In January 2006, researchers from the University of Athens analyzed teeth recovered from a mass grave underneath the city, confirmed the presence of bacteria responsible for typhoid. Antonine Plague, 165–180 AD. Smallpox brought to the Italian peninsula by soldiers returning from the Near East. At the height of a second outbreak, the Plague of Cyprian, which may have been the same disease, 5,000 people a day were said to be dying in Rome. Plague of Justinian, from 541 to 750, was the first recorded outbreak of the bubonic plague, it started in Egypt, reached Constantinople the following spring, killing 10,000 a day at its height, 40% of the city's inhabitants. The plague went on to eliminate a quarter to a half of the human population that it struck throughout the known world.
It caused Europe's population to drop by around 50% between 550 and 700. Black Death, from 1331 to 1353; the total number of deaths worldwide is estimated at 75 million people. Eight hundred years after the last outbreak, the plague returned to Europe. Starting in Asia, the disease reached Mediterranean and western Europe in 1348, killed an estimated 20 to 30 million Europeans in six years, it was the first of a cycle of European plague epidemics. There were more than 100 plague epidemics in Europe in this period; the disease recurred in England every two to five years from 1361 to 1480. By the 1370s
1931 China floods
The 1931 China floods or the 1931 Yangtze-Huai River floods were a series of devastating floods that occurred in the Republic of China. They were some of the deadliest floods in history, together formed one of the most lethal natural disasters of the 20th century, excluding pandemics and famines. Estimates of the total death toll range from 422,499 to between 3.7 4 million. From 1928 to 1930, China was afflicted by a long drought; the subsequent winter of 1930 was harsh, creating large deposits of snow and ice in mountainous areas. Early 1931, melting snow and ice flowed downstream and arrived in the middle Yangtze during a period of heavy spring rain. Ordinarily, the region experienced three periods of high water during the spring and autumn. By June, those living in low areas had been forced to abandon their homes; the summer was characterized by extreme cyclonic activity. In July of that year alone, nine cyclones hit the region, above the average of two per year. Four weather stations along the Yangtze River reported rain totaling over 600 mm for the month.
The water flowing through the Yangtze reached its highest level since record-keeping began in the mid-nineteenth century. That autumn, further heavy rain added to the problem and some rivers did not return to their normal courses until November; the floods inundated 180,000 km2 – an area equivalent in size to England and half of Scotland, or the states of New York, New Jersey and Connecticut combined. The high-water mark recorded on 19 August at Hankou in Wuhan showed water levels 16 m above the average, an average of 1.7 m above the Shanghai Bund. In Chinese, this event is known as 江淮水灾, which translates to "Yangtze-Huai Flood Disaster." This name, fails to capture the massive scale of flooding. Waterways throughout much of the country were inundated the Yellow River and Grand Canal; the eight most affected provinces were Anhui, Hunan, Zhejiang, Jiangxi and Shandong. Beyond the core flood zone, areas as far south as Guangdong, as far north as Manchuria, as far west as Sichuan were inundated. At the time the government estimated.
Historians since have suggested. Estimated death tolls vary widely. Contemporary studies conducted by John Lossing Buck suggested that at least 150,000 people had drowned in the first few months of the flood, with hundreds of thousands more dying of starvation and disease over the following year. Using contemporary media reports, Chinese historians led by Li Wenhai have calculated the death toll at around 422,499. Contemporary government sources suggested; some Western sources have given a far higher death toll of between 4 million people. The flood farmland. Throughout the whole Yangtze Valley around 15% of the wheat and rice crops were destroyed, with the proportion being much higher in the flood affected areas; the disaster caused an economic shock with the price of vital commodities rising rapidly. The combined ecological and economic impacts of the disaster caused many areas to descend into famine. With no food, people were reduced to eating tree bark and earth; some sold their children to survive.
The most lethal effect of the flood was the diseases that swept through the refugee population due to displacement and the breakdown of sanitation. These included cholera, malaria and schistosomiasis; as well as inundating rural areas, the flood caused widespread destruction to a number of cities. Refugees had been arriving in the city of Wuhan since the late spring; when the city itself was inundated in the early summer and after a catastrophic dike failure at just before 6:00 AM on July 27, around 782,189 urban citizens and rural refugees were left homeless. The flood covered an area of 32 square miles and the city was flooded under many feet of water for close to three months. Large numbers gathered on flood islands throughout the city, with 30,000 sheltering on a railway embankment in central Hankou. With little food and a complete breakdown in sanitation, thousands soon began to succumb to diseases. There was no warning, only a sudden great wall of water. Most of Wuhan's buildings in those days were only one story high, for many people there was no escape- they died by the tens of thousands....
I was just coming off duty at the company's main office, a new three-story building near the center of town... When I heard the terrible noise and saw the wall of water coming, I raced to the top story of the building.... I was in one of the tallest and strongest buildings left standing. At that time no one knew whether the water would subside or rise higher; the city of Nanjing the capital of Republican China, was severely affected by the disaster. One of the most tragic single events during the flood occurred on 25 August 1931, when the water rushing through the Grand Canal washed away dikes near Gaoyou Lake. In Gaoyou County alone, 18,000 people drowned and 58,000 died due to famine and diseases the following year; the 1931 flood was one of the first major tests for the Kuomintang Government. As the scale of the disaster became apparent, the government established the National Flood Relief Commission under the auspices Song Ziwen, a prominent politician in the Kuomintang and brother-in-law of Chiang Kai-shek.
The commission employed a range of Chinese and foreign experts, including figures such as the famous epidemiologist Wu Lian
Homelessness is defined as living in housing, below the minimum standard or lacks secure tenure. People can be categorized as homeless; the legal definition of homeless varies from country to country, or among different jurisdictions in the same country or region. According to the UK homelessness charity Crisis, a home is not just a physical space: it provides roots, security, a sense of belonging and a place of emotional wellbeing. United States government homeless enumeration studies include people who sleep in a public or private place not designed for use as a regular sleeping accommodation for human beings. People who are homeless are most unable to acquire and maintain regular, safe and adequate housing due to a lack of, or an unsteady income. Homelessness and poverty are interrelated. In 2005, an estimated 100 million people worldwide were homeless and as many as 1 billion people live as squatters, refugees or in temporary shelter, all lacking adequate housing. In Western countries, the majority of homeless are men, with single males overrepresented.
However, current data suggests similar rates of homeless females. In 2015, the United States reported that there were 564,708 homeless people within its borders, one of the higher reported figures worldwide; these figures are underestimates as surveillance for the homeless population is challenging. When compared to the general population, people who are homeless experience higher rates of adverse physical and mental health outcomes, which renders them vulnerable to health conditions associated with climate change. Chronic disease severity, respiratory conditions, rates of mental health illnesses and substance use are all greater in homeless populations than the general population. Homelessness is associated with a high risk of suicide attempts. People experiencing homelessness have limited access to resources and are disengaged from health services, making them that much more susceptible to extreme weather events and ozone levels; these disparities result in increased morbidity and mortality in the homeless population.
There are a number of organizations. Most countries provide a variety of services to assist homeless people; these services provide food and clothing and may be organized and run by community organizations or by government departments or agencies. These programs may be supported by the government, charities and individual donors. Many cities have street newspapers, which are publications designed to provide employment opportunity to homeless people. While some homeless have jobs, some must seek other methods to make a living. Begging or panhandling is one option, but is becoming illegal in many cities. People who are homeless may have additional conditions, such as physical or mental health issues or substance addiction. Homeless people, homeless organizations, are sometimes accused or convicted of fraudulent behaviour. Criminals are known to exploit homeless people, ranging from identity theft to tax and welfare scams; these incidents lead to negative connotations on the homeless as a group. In 2004, the United Nations sector of Economic and Social Affairs defined a homeless household as those households without a shelter that would fall within the scope of living quarters due to a lack of or a steady income.
They carry their few possessions with them, sleeping in the streets, in doorways or on piers, or in another space, on a more or less random basis. In 2009, at the United Nations Economic Commission for Europe Conference of European Statisticians, held in Geneva, the Group of Experts on Population and Housing Censuses defined homelessness as: In its Recommendations for the Censuses of Population and Housing, the CES identifies homeless people under two broad groups: Primary homelessness; this category includes persons living in the streets without a shelter that would fall within the scope of living quarters. This category may include persons with no place of usual residence who move between various types of accommodations; this category includes persons living in private dwellings but reporting'no usual address' on their census form. The CES acknowledges that the above approach does not provide a full definition of the'homeless'. Article 25 of the Universal Declaration of Human Rights, adopted 10 December 1948 by the UN General Assembly, contains this text regarding housing and quality of living: Everyone has the right to a standard of living adequate for the health and well-being of himself and of his family, including food, clothing and medical care and necessary social services, the right to security in the event of unemployment, disability, old age or other lack of livelihood in circumstances beyond his control.
Homelessness is addressed differently according to country. The European Typology of Homelessness and Housing Exclusion was developed as a means of improving understanding and measurement of homelessness in Europe, to provide a common "language" for transnational exchanges on homelessness; the ETHOS approach confirms that homelessne
Zhengzhou is the capital of Henan Province in the central part of the People's Republic of China. It is one of the National Central Cities in China, the centre of Central Plains area and serves as the political, economic and educational center of the province, as well as a major transportation hub in China; the Zhengzhou metropolitan area is the core area of the Central Plains Economic Zone. Zhengzhou is a National Civilized City, State-list Famous Historical and Culture City, one of the Eight Ancient Capital Cities and one of the birthplaces of Chinese Civilization, the birthplace of the Yellow Emperor. Zhengzhou was the capital of China for a thousand years. There are two World Cultural Heritage Sites in Zhengzhou; the Zhengzhou Commodity Exchange is China's first futures exchange, Zhengzhou Airport Economy Zone is China's first Airport Economy Zone. The city lies on the southern bank of the Yellow River, is one of the Eight Great Ancient Capitals of China; as a center of China's national transportation network, there are railways connecting Zhengzhou and Europe, a bustling international airport.
Zhengzhou has a population of 10,120,000 inhabitants,and had a GDP of 1,014 billion in 2018. The city is one of the main built-up areas of Henan region. Greater Zhengzhou was named as one of the 13 emerging mega-cities in China in a July 2012 report by the Economist Intelligence Unit, named as the eighth National Central City in 2017 by the central government in Beijing. In 2011, a Journeyman documentary showcased the developments of the Zhengdong New Area of Zhengzhou as a ghost city. However, by 2016, the district had over 1.42 million residents and became the financial hub of Henan Province. The Shang dynasty established Bodu in Zhengzhou; this prehistorical city had become abandoned as ruins long before the First Emperor of China in BC 260. Since 1950, archaeological finds in a walled city in Eastern Zhengzhou have provided evidence of Neolithic Shang dynasty settlements in the area. Outside this city, remains of large public buildings and a complex of small settlements have been discovered.
The site is identified with the Shang capital of Ao and is preserved in the Shang dynasty Ruins monument in Guanchen District. The Shang, who continually moved their capital due to frequent natural disasters, left Ao at around 13th century BC; the site remained occupied. Legend suggests. From this derives the name borne by the county since the late 6th century BC—Guancheng; the city first became the seat of a prefectural administration in AD 587, when it was named Guanzhou. In 605 it was first called Zhengzhou—a name by which it has been known ever since; the name Zhengzhou came from the Sui dynasty though it was located in Chenggao, another town. The government moved to the contemporary city during the Tang dynasty, it achieved its greatest importance under the Sui and early Song dynasties, when it was the terminus of the New Bian Canal, which joined the Yellow River to the northwest. There, at a place called Heyin, a vast granary complex was established to supply the capitals at Luoyang and Chang'an to the west and the frontier armies to the north.
In the Song period, the transfer of the capital eastward to Kaifeng robbed Zhengzhou of much of its importance. It was a capital during the five dynasties of Xia, Guan and Han, a prefecture during the eight dynasties of Sui, Five Dynasties, Jin, Yuan and Qing. In 1903 the Beijing–Hankou Railway arrived at Zhengzhou, in 1909 the first stage of the Longhai Railway gave it an east–west link to Kaifeng and Luoyang. Zhengzhou thus became a major rail junction and a regional center for cotton, grain and other agricultural produce. Early in 1923 a workers' strike began in Zhengzhou and spread along the rail line before it was suppressed. On June 10, 1938, Chiang Kai-shek's National Revolutionary Army opened up the dikes retaining the Yellow River at Huayuankou between Zhengzhou and Kaifeng, in an effort to stem the tide of invading Japanese. Zhengzhou has a locomotive and rolling-stock repair plant, a tractor-assembly plant, a thermal generating station; the city's industrial growth has resulted in a large increase in the population, coming predominantly from industrial workers from the north.
A water diversion project and pumping station, built in 1972, has provided irrigation for the surrounding countryside. The city has an agricultural university. Zhengzhou is divided into 5 county-level cities and 1 county; these subdivisions are to undergo significant changes in the near future due to rapid urban expansion and urban planning. The municipality is home to 8,626,505 inhabitants and 6,35 million in its built up area made of 6 urban and suburban districts and Xinzheng cities and now Zhongmu county being urbanized, making the city one of the main built-up areas of the province. Located just north of the province's centre and south of the Yellow River, Zhengzhou borders Luoyang to the west, Jiaozuo to the northwest, Xinxiang
A flood is an overflow of water that submerges land, dry. In the sense of "flowing water", the word may 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, 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 occur in rivers when the flow rate exceeds the capacity of the river channel at bends or meanders in the waterway. Floods 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 flat and fertile and because rivers provide easy travel and access to commerce and industry. Some floods develop 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 large, affecting entire river basins; the word "flood" comes from a word common to Germanic languages. Floods can happen on flat or low-lying areas when water is supplied by rainfall or snowmelt more than it can either infiltrate or run off; the excess accumulates in place, sometimes to hazardous depths. Surface soil can become saturated, which stops infiltration, where the water table is shallow, such as a floodplain, or from intense rain from one or a series of storms. Infiltration is slow to negligible through frozen ground, 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. 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, debris, or beaver dams. Slow-rising floods most 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 intense in smaller areas of those basins.
Rapid flooding events, including flash floods, more 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 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 in just one minute. 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 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. The leading edge of the flood thus advances more than and higher flows; as a result, the rising limb of the hydrograph becomes quicker as the flood moves downstream, until the flow rate is so great that the depletion by wetting soil becomes insignificant. Flooding in estuaries is caused by a combination of sea tidal surges caused by winds and low barometric pressure, 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 explains: "Storm surge is an abnormal rise of water generated by a storm and above the predicted astronomical tides. Storm surge should not be confused with storm tide, 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 when storm surge coincides with normal high tide, resulting in storm tides reaching up to 20 feet or more in some cases." Urban flooding is the inundation of land or property in a built environment in more densely populated areas, caused by rainfall overwhelmi
China the People's Republic of China, is a country in East Asia and the world's most populous country, with a population of around 1.404 billion. Covering 9,600,000 square kilometers, it is the third- or fourth-largest country by total area. Governed by the Communist Party of China, the state exercises jurisdiction over 22 provinces, five autonomous regions, four direct-controlled municipalities, the special administrative regions of Hong Kong and Macau. China emerged as one of the world's earliest civilizations, in the fertile basin of the Yellow River in the North China Plain. For millennia, China's political system was based on hereditary monarchies, or dynasties, beginning with the semi-legendary Xia dynasty in 21st century BCE. Since China has expanded, re-unified numerous times. In the 3rd century BCE, the Qin established the first Chinese empire; the succeeding Han dynasty, which ruled from 206 BC until 220 AD, saw some of the most advanced technology at that time, including papermaking and the compass, along with agricultural and medical improvements.
The invention of gunpowder and movable type in the Tang dynasty and Northern Song completed the Four Great Inventions. Tang culture spread in Asia, as the new Silk Route brought traders to as far as Mesopotamia and Horn of Africa. Dynastic rule ended in 1912 with the Xinhai Revolution; the Chinese Civil War resulted in a division of territory in 1949, when the Communist Party of China established the People's Republic of China, a unitary one-party sovereign state on Mainland China, while the Kuomintang-led government retreated to the island of Taiwan. The political status of Taiwan remains disputed. Since the introduction of economic reforms in 1978, China's economy has been one of the world's fastest-growing with annual growth rates above 6 percent. According to the World Bank, China's GDP grew from $150 billion in 1978 to $12.24 trillion by 2017. Since 2010, China has been the world's second-largest economy by nominal GDP and since 2014, the largest economy in the world by purchasing power parity.
China is the world's largest exporter and second-largest importer of goods. China is a recognized nuclear weapons state and has the world's largest standing army and second-largest defense budget; the PRC is a permanent member of the United Nations Security Council as it replaced the ROC in 1971, as well as an active global partner of ASEAN Plus mechanism. China is a leading member of numerous formal and informal multilateral organizations, including the Shanghai Cooperation Organization, WTO, APEC, BRICS, the BCIM, the G20. In recent times, scholars have argued that it will soon be a world superpower, rivaling the United States; the word "China" has been used in English since the 16th century. It is not a word used by the Chinese themselves, it has been traced through Portuguese and Persian back to the Sanskrit word Cīna, used in ancient India."China" appears in Richard Eden's 1555 translation of the 1516 journal of the Portuguese explorer Duarte Barbosa. Barbosa's usage was derived from Persian Chīn, in turn derived from Sanskrit Cīna.
Cīna was first used including the Mahābhārata and the Laws of Manu. In 1655, Martino Martini suggested that the word China is derived from the name of the Qin dynasty. Although this derivation is still given in various sources, it is complicated by the fact that the Sanskrit word appears in pre-Qin literature; the word may have referred to a state such as Yelang. The meaning transferred to China as a whole; the origin of the Sanskrit word is still a matter of debate, according to the Oxford English Dictionary. The official name of the modern state is the "People's Republic of China"; the shorter form is "China" Zhōngguó, from zhōng and guó, a term which developed under the Western Zhou dynasty in reference to its royal demesne. It was applied to the area around Luoyi during the Eastern Zhou and to China's Central Plain before being used as an occasional synonym for the state under the Qing, it was used as a cultural concept to distinguish the Huaxia people from perceived "barbarians". The name Zhongguo is translated as "Middle Kingdom" in English.
Archaeological evidence suggests that early hominids inhabited China between 2.24 million and 250,000 years ago. The hominid fossils of Peking Man, a Homo erectus who used fire, were discovered in a cave at Zhoukoudian near Beijing; the fossilized teeth of Homo sapiens have been discovered in Fuyan Cave in Hunan. Chinese proto-writing existed in Jiahu around 7000 BCE, Damaidi around 6000 BCE, Dadiwan from 5800–5400 BCE, Banpo dating from the 5th millennium BCE; some scholars have suggested. According to Chinese tradition, the first dynasty was the Xia, which emerged around 2100 BCE; the dynasty was considered mythical by historians until scientific excavations found early Bronze Age sites at Erlitou, Henan in 1959. It remains unclear whether these sites are the remains of the Xia dynasty or of another culture from the same period; the succeeding Shang dynasty is the earliest to be confirmed by contemporary records. The Shang ruled the plain of the Yellow River in eastern China from the 17th to the 11th century BCE.
Their oracle bone script
The Yellow River or Huang He is the second longest river in China, after the Yangtze River, the sixth longest river system in the world at the estimated length of 5,464 km. Originating in the Bayan Har Mountains in Qinghai province of Western China, it flows through nine provinces, 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 and a north–south extent of about 1,100 km. Its total drainage area is about 752,546 square kilometers, its basin was the birthplace of ancient Chinese civilization, 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. Early Chinese literature including the Yu Gong or Tribute of Yu dating to the Warring States period refers to the Yellow River as 河, a character that has come to mean "river" in modern usage.
The first appearance of the name 黃河 is in the Book of Han written during the Eastern Han dynasty about the Western Han dynasty. The adjective "yellow" describes the perennial color of the muddy water in the lower course of the river, which arises from soil being carried downstream. One of its older Mongolian names was the "Black River", because the river runs clear before it enters the Loess Plateau, but the current name of the river among Inner Mongolians is Ȟatan Gol. In Mongolia itself, it is called the Šar Mörön. In Qinghai, the river's Tibetan name is "River of the Peacock" The Yellow River is one of several rivers that are essential for China's existence. At the same time, however, it has been responsible for several deadly floods, including the only natural disasters in recorded history to have killed more than a million people; the deadliest was a Yuan dynasty 1332 -- 33 flood. Close behind during the Qing dynasty is the 1887 flood, which killed anywhere from 900,000 to 2 million people, a Republic of China era 1931 flood that killed 1–4 million people.
The cause of the floods is the large amount of fine-grained loess carried by the river from the Loess Plateau, continuously deposited along the bottom of its channel. The sedimentation causes natural dams to accumulate; these subaqueous dams were unpredictable and undetectable. The enormous amount of water has to find a new way to the sea, forcing it to take the path of least resistance; when this happens, it bursts out across the flat North China Plain, sometimes taking a new channel and inundating any farmland, cities or towns in its path. The traditional Chinese response of building higher and higher levees along the banks sometimes contributed to the severity of the floods: When flood water did break through the levees, it could no longer drain back into the river bed as it would after a normal flood as the river bed was sometimes now higher than the surrounding countryside; these changes could cause the river's mouth to shift as much as 480 km, sometimes reaching the ocean to the north of Shandong Peninsula and sometimes to the south.
Another historical source of devastating floods is the collapse of upstream ice dams in Inner Mongolia with an accompanying sudden release of vast quantities of impounded water. There have been 11 such major floods in the past century, each causing tremendous loss of life and property. Nowadays, explosives dropped from aircraft are used to break the ice dams before they become dangerous. Before modern dams came to China, the Yellow River used to be prone to flooding. In the 2,540 years from 595 BC to 1946 AD, the Yellow River has been reckoned to have flooded 1,593 times, shifting its course 26 times noticeably and nine times severely; these floods include some of the deadliest natural disasters recorded. Before modern disaster management, when floods occurred, some of the population might die from drowning but many more would suffer from the ensuing famine and spread of diseases. In Chinese mythology, the giant Kua Fu drained the Yellow River and the Wei River to quench his burning thirst as he pursued the Sun.
Historical documents from the Spring and Autumn period and Qin dynasty indicate that the Yellow River at that time flowed north of its present course. These accounts show that after the river passed Luoyang, it flowed along the border between Shanxi and Henan Provinces continued along the border between Hebei and Shandong before emptying into Bohai Bay near present-day Tianjin. Another outlet followed the present course; the river left these paths in 602 BC and shifted south of the Shandong Peninsula. Sabotage of dikes and reservoirs and deliberate flooding of rival states became a standard military tactic during the Warring States period; as the Yellow River valley was the major entryway to the Guanzhong area and the state of Qin from the North China Plain, Qin fortified the Hangu Pass. Major flooding in AD 11 is credited with the downfall of the short-lived Xin dynasty, another flood in AD 70 returned the river north of Shandong on its present course. From around the beginning of the 3rd century, the importance of the Hangu Pass was reduced, with the major fortifications a