River delta

A river delta is a landform that forms from deposition of sediment carried by a river as the flow leaves its mouth and enters slower-moving or standing water. This occurs where a river enters an ocean, sea, estuary, lake, reservoir, or (more rarely) another river that cannot transport away the supplied sediment.

Despite a popular legend, this use of the word delta was not coined by Herodotus.

Formation

River deltas form when a river carrying sediment reaches either (1) a body of standing water, such as a lake, ocean, or reservoir, (2) another river that cannot remove the sediment quickly enough to stop delta formation, or (3) an inland region where the water spreads out and deposits sediments. The tidal currents also cannot be too strong, as sediment would wash out into the water body faster than the river deposits it. Of course, the river must carry enough sediment to layer into deltas over time. The river's velocity decreases rapidly, causing it to deposit the majority, if not all, of its load. This alluvium builds up to form the river delta. When the flow enters the standing water, it is no longer confined to its channel and expands in width. This flow expansion results in a decrease in the flow velocity, which diminishes the ability of the flow to transport sediment. As a result, sediment drops out of the flow and deposits. Over time, this single channel builds a deltaic lobe (such as the bird's-foot of the Mississippi or Ural river deltas), pushing its mouth into the standing water. As the deltaic lobe advances, the gradient of the river channel becomes lower because the river channel is longer but has the same change in elevation (see slope).

Pearl River Delta

The Pearl River Delta (PRD), Zhujiang Delta or Zhusanjiao in Guangdong province, China is the low-lying area surrounding the Pearl River estuary where the Pearl River flows into the South China Sea. It is one of the most densely urbanised regions in the world and one of the main hubs of China's economic growth. This region is often considered an emerging megacity. The PRD is a megalopolis, with future development into a single mega metropolitan area, yet itself is at the southern end of a larger megalopolis running along the southern coast of China, which include large metropolises like Chaoshan, Zhangzhou-Xiamen, Quanzhou-Putian, and Fuzhou. The nine largest cities of PRD had a combined population of 57.15 million at the end of 2013, however their annual population growth rate is modest at 0.45%, comprising 53.69% of the provincial population. This sharply contrasts with the previous decade's migrant population boom, and reflects the rising cost of migrant labor and changes to the value chain. According to the World Bank Group, the PRD has become the largest urban area in the world in both size and population.

Pearl River

Pearl River may refer to:

Bodies of water

Communities and administrative divisions

In the United States:

In music

Hong Kong

Hong Kong (香港; "Fragrant Harbour"), officially Hong Kong Special Administrative Region of the People's Republic of China, is an autonomous territory on the southern coast of China at the Pearl River Estuary and the South China Sea. Hong Kong is known for its skyline and deep natural harbour. It has a land area of 1104 km² and shares its northern border with Guangdong Province of Mainland China. With around 7.2 million inhabitants of various nationalities, Hong Kong is one of the world's most densely populated metropolises.

After the First Opium War (1839–42), Hong Kong became a British colony with the perpetual cession of Hong Kong Island, followed by Kowloon Peninsula in 1860 and a 99-year lease of the New Territories from 1898. Hong Kong remained under British control for about a century until the Second World War, when Japan occupied the colony from December 1941 to August 1945. After the Surrender of Japan, the British resumed control. In the 1980s, negotiations between the United Kingdom and the China resulted in the 1984 Sino-British Joint Declaration, which provided for the transfer of sovereignty of Hong Kong on 30 June 1997. The territory became a special administrative region of China with a high degree of autonomy on 1 July 1997 under the principle of one country, two systems. Disputes over the perceived misapplication of this principle have contributed to popular protests, including the 2014 Umbrella Revolution.

Delta

Delta commonly refers to:

Delta may also refer to:

Places

Canada

United States

Uruguay

Organizations