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63-1102: The first German trading post in the Duala area on the Kamerun River delta was established in 1868 by the Hamburg trading company C. Woermann  [ de ] . The firm's primary agent in Gabon , Johannes Thormählen, expanded activities to the Kamerun River delta. In 1874, together with the Woermann agent in Liberia , Wilhelm Jantzen, the two merchants founded their own company, Jantzen & Thormählen there. Both of these West Africa houses expanded into shipping with their own sailing ships and steamers and inaugurated scheduled passenger and freight service between Hamburg and Duala. These companies and others obtained extensive acreage from local chiefs and began systematic plantation operations, including bananas. The Cameroon territory

126-432: A density current that deposits its sediments as turbidites . When the river water is less dense than the basin water, as is typical of river deltas on an ocean coastline, the delta is characterized by hypopycnal flow in which the river water is slow to mix with the denser basin water and spreads out as a surface fan. This allows fine sediments to be carried a considerable distance before settling out of suspension. Beds in

189-578: A colony would only function as an economic drain. This perspective would change in the early 1880s, due to a variety of internal pressures. The two key factors motivating this change were pressure from economic interests in Germany, and concerns about missing out on what would later be called the Scramble for Africa . On the political side, colonies became a point of national pride, as Germans saw that other nations had colonies, and thought they should too as

252-493: A common location for civilizations to flourish due to access to flat land for farming, freshwater for sanitation and irrigation , and sea access for trade. Deltas often host extensive industrial and commercial activities, and agricultural land is frequently in conflict. Some of the world's largest regional economies are located on deltas such as the Pearl River Delta , Yangtze River Delta , European Low Countries and

315-545: A delta but enter into the sea in the form of an estuary . Notable examples include the Gulf of Saint Lawrence and the Tagus estuary. In rare cases, the river delta is located inside a large valley and is called an inverted river delta . Sometimes a river divides into multiple branches in an inland area, only to rejoin and continue to the sea. Such an area is called an inland delta , and often occurs on former lake beds. The term

378-558: A directly administered colony, opted to instead grant the companies already involved in Cameroon a "Chartered" status. As such, initial government fell to large German trading companies and concession companies who had already established themselves in the colony. Eventually, however, it was revealed that the companies were not performing their administrative duties very well. A variety of factors contributed to their failure, but foremost among them were ongoing conflicts with local traders as

441-533: A fan. The more often the flow changes course, the shape develops closer to an ideal fan because more rapid changes in channel position result in a more uniform deposition of sediment on the delta front. The Mississippi and Ural River deltas, with their bird's feet, are examples of rivers that do not avulse often enough to form a symmetrical fan shape. Alluvial fan deltas, as seen by their name, avulse frequently and more closely approximate an ideal fan shape. Most large river deltas discharge to intra-cratonic basins on

504-399: A few main distributaries. Once a wave-dominated or river-dominated distributary silts up, it is abandoned, and a new channel forms elsewhere. In a tidal delta, new distributaries are formed during times when there is a lot of water around – such as floods or storm surges . These distributaries slowly silt up at a more or less constant rate until they fizzle out. A tidal freshwater delta is

567-545: A flat arid area splits into channels that evaporate as it progresses into the desert. The Okavango Delta in Botswana is one example. See endorheic basin . The generic term mega delta can be used to describe very large Asian river deltas, such as the Yangtze , Pearl , Red , Mekong , Irrawaddy , Ganges-Brahmaputra , and Indus . The formation of a delta is complicated, multiple, and cross-cutting over time, but in

630-573: A hypocynal delta dip at a very shallow angle, around 1 degree. Fluvial-dominated deltas are further distinguished by the relative importance of the inertia of rapidly flowing water, the importance of turbulent bed friction beyond the river mouth, and buoyancy . Outflow dominated by inertia tends to form Gilbert-type deltas. Outflow dominated by turbulent friction is prone to channel bifurcation, while buoyancy-dominated outflow produces long distributaries with narrow subaqueous natural levees and few channel bifurcations. The modern Mississippi River delta

693-504: A matter of national prestige. Several government officials took this stance, and it seemed to enjoy public support as well. On the commercial side, the companies already operating in Cameroon (represented by the likes of Adolph Woermann) wanted the protection and support an official German colony would provide, and many German producers sought new markets for their excess goods. These pressures would eventually culminate in Bismarck allowing

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756-439: A mature delta with a distributary network. Another way these distributary networks form is from the deposition of mouth bars (mid-channel sand and/or gravel bars at the mouth of a river). When this mid-channel bar is deposited at the mouth of a river, the flow is routed around it. This results in additional deposition on the upstream end of the mouth bar, which splits the river into two distributary channels. A good example of

819-412: A number of tribes of the regions around the rivers, where trade was already well established. This would establish a trend of using treaties as one method of expanding German control. As mentioned above, one of the primary motivations for the colony was German corporations seeking to expand their economic interests in Cameroon. Bismarck, being aware of this fact and concerned about the substantial costs of

882-463: A prison sentence of nine years. By 1906, news of Bell's arrest and the events in Kamerun had led to a public outcry, and Puttkamer was finally put on trial. During the trial, Puttkamer was found guilty of acts of insubordination , and was made to pay a fine of 1,000 Reichsmarks . On 9 May 1907, Puttkamer was dismissed as governor by German colonial secretary Bernhard Dernburg . Puttkamer had built

945-761: A result of his frivolous lifestyle, Puttkamer was sent to the newly-established German colony of Kamerun in Africa, where he became a colonial diplomat, and was also drafted into the Imperial German Army as an officer in the Schutztruppe . He was eventually appointed by governor Julius von Soden to serve as Deputy Governor, a position which he served until 1890, after which he worked as a German diplomat in Nigeria . From 1892 to 1895, Puttkamer served as Landeshauptmann of Togoland . Jesko von Puttkamer

1008-423: A sedimentary deposit formed at the boundary between an upland stream and an estuary, in the region known as the "subestuary". Drowned coastal river valleys that were inundated by rising sea levels during the late Pleistocene and subsequent Holocene tend to have dendritic estuaries with many feeder tributaries. Each tributary mimics this salinity gradient from its brackish junction with the mainstem estuary up to

1071-447: A simple delta three main types of bedding may be distinguished: the bottomset beds, foreset/frontset beds, and topset beds. This three-part structure may be seen on small scale by crossbedding . Human activities in both deltas and the river basins upstream of deltas can radically alter delta environments. Upstream land use change such as anti-erosion agricultural practices and hydrological engineering such as dam construction in

1134-551: Is a good example of a fluvial-dominated delta whose outflow is buoyancy-dominated. Channel abandonment has been frequent, with seven distinct channels active over the last 5000 years. Other fluvial-dominated deltas include the Mackenzie delta and the Alta delta. A Gilbert delta (named after Grove Karl Gilbert ) is a type of fluvial-dominated delta formed from coarse sediments, as opposed to gently sloping muddy deltas such as that of

1197-410: Is a major sign that Mars once had large amounts of water. Deltas have been found over a wide geographical range. Below are pictures of a few. Jesko von Puttkamer Jesko Albert Eugen von Puttkamer (2 July 1855 – 23 January 1917) was a German diplomat, colonial administrator, and military officer who served as colonial governor of German Kamerun from 1895 to 1907. Jesko von Puttkamer

1260-591: Is called by the Ionians ", including describing the outflow of silt into the sea and the convexly curved seaward side of the triangle. Despite making comparisons to other river systems deltas, Herodotus did not describe them as "deltas". The Greek historian Polybius likened the land between the Rhône and Isère rivers to the Nile Delta, referring to both as islands, but did not apply the word delta. According to

1323-548: Is so named because the shape of the Nile Delta approximates the triangular uppercase Greek letter delta . The triangular shape of the Nile Delta was known to audiences of classical Athenian drama ; the tragedy Prometheus Bound by Aeschylus refers to it as the "triangular Nilotic land", though not as a "delta". Herodotus 's description of Egypt in his Histories mentions the Delta fourteen times, as "the Delta, as it

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1386-662: The Greater Tokyo Area . The Ganges–Brahmaputra Delta , which spans most of Bangladesh and West Bengal and empties into the Bay of Bengal , is the world's largest delta. The Selenga River delta in the Russian republic of Buryatia is the largest delta emptying into a body of fresh water, in its case Lake Baikal . Researchers have found a number of examples of deltas that formed in Martian lakes . Finding deltas

1449-591: The Manenguba mountains, and the 300-kilometre (190 mi) mainline went to Makak on the river Nyong . An extensive postal and telegraph system and a river navigation network with government ships connected the coast to the interior. The Cameroon protectorate was enlarged with New Cameroon (German: Neukamerun) in 1911 as part of the settlement of the Agadir Crisis , resolved by the Treaty of Fez . At

1512-532: The Nile Delta and Colorado River Delta are some of the most extreme examples of the devastation caused to deltas by damming and diversion of water. Historical data documents show that during the Roman Empire and Little Ice Age (times when there was considerable anthropogenic pressure), there was significant sediment accumulation in deltas. The industrial revolution has only amplified the impact of humans on delta growth and retreat. Ancient deltas benefit

1575-411: The deposition of the sediments that are carried by the waters of a river , where the river merges with a body of slow-moving water or with a body of stagnant water. The creation of a river delta occurs at the river mouth , where the river merges into an ocean , a sea , or an estuary , into a lake , a reservoir , or (more rarely) into another river that cannot carry away the sediment supplied by

1638-467: The 1920s and 30s. It would take until World War II before Germany was "fully out" of Cameroon. In 1914 a series of drafts were made for proposed coat of arms and flags for the German Colonies . However, World War I broke out before the designs were finished and implemented and the symbols were never actually used. River delta A river delta is a triangular landform created by

1701-673: The German behaviors that lend them a reputation of brutality and harshness as colonizers. During his time, he oversaw a number of military campaigns against local peoples like the Bali, forcing those who rebuffed German attempts at a "treaty" that supposedly justified German expansion. Oftentimes, he would not act directly against these people, instead relying on empowering other rival local powers and establishing them as "protected by Germany" and arming them. These groups would then use their newfound power and armaments to conquer dissenting peoples, without

1764-490: The Germans themselves actually ever getting involved. When the Germans did become involved, however, it was brutal, often going out of their way to punish those who surrendered to them if their leader still refused, and taking a tithe of people from conquered peoples as essentially slaves, though they did not call them such. This leads into the second prominent feature of Puttkamer's governorship, his expansion and support for

1827-700: The Greek geographer Strabo , the Cynic philosopher Onesicritus of Astypalaea , who accompanied Alexander the Great 's conquests in India , reported that Patalene (the delta of the Indus River ) was "a delta" ( Koinē Greek : καλεῖ δὲ τὴν νῆσον δέλτα , romanized:  kalei de tēn nēson délta , lit.   'he calls the island a delta'). The Roman author Arrian 's Indica states that "the delta of

1890-503: The Mississippi. For example, a mountain river depositing sediment into a freshwater lake would form this kind of delta. It is commonly a result of homopycnal flow. Such deltas are characterized by a tripartite structure of topset, foreset, and bottomset beds. River water entering the lake rapidly deposits its coarser sediments on the submerged face of the delta, forming steeping dipping foreset beds. The finer sediments are deposited on

1953-472: The ability to pile up and accumulate due to the sediment traveling into a steep subduction trench rather than a shallow continental shelf . There are many other lesser factors that could explain why the majority of river deltas form along passive margins rather than active margins. Along active margins, orogenic sequences cause tectonic activity to form over-steepened slopes, brecciated rocks, and volcanic activity resulting in delta formation to exist closer to

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2016-472: The agricultural industry, and efforts were taken to expand further into the landlocked areas of Cameroon to better trade opportunities and German access to the African interior. The most notable of the German governors, and the man who would come to define the German legacy in Cameroon, would be Jesko Von Puttkammer , who governed from 1895–1906 (and for a few shorter times before). It was Puttkammer who began

2079-1256: The basins feeding deltas have reduced river sediment delivery to many deltas in recent decades. This change means that there is less sediment available to maintain delta landforms, and compensate for erosion and sea level rise , causing some deltas to start losing land. Declines in river sediment delivery are projected to continue in the coming decades. The extensive anthropogenic activities in deltas also interfere with geomorphological and ecological delta processes. People living on deltas often construct flood defences which prevent sedimentation from floods on deltas, and therefore means that sediment deposition can not compensate for subsidence and erosion . In addition to interference with delta aggradation , pumping of groundwater , oil , and gas , and constructing infrastructure all accelerate subsidence , increasing relative sea level rise. Anthropogenic activities can also destabilise river channels through sand mining , and cause saltwater intrusion . There are small-scale efforts to correct these issues, improve delta environments and increase environmental sustainability through sedimentation enhancing strategies . While nearly all deltas have been impacted to some degree by humans,

2142-422: 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 ). As the gradient of the river channel decreases, the amount of shear stress on the bed decreases, which results in the deposition of sediment within

2205-450: The channel and a rise in the channel bed relative to the floodplain . This destabilizes the river channel. If the river breaches its natural levees (such as during a flood), it spills out into a new course with a shorter route to the ocean, thereby obtaining a steeper, more stable gradient. Typically, when the river switches channels in this manner, some of its flow remains in the abandoned channel. Repeated channel-switching events build up

2268-403: The cutting of hands, genitals, gouging of eyes and decapitations. Severed limbs were often collected and shown to local authorities as proof of death. These practices, which continued even after Puttkammer retired from his position, would define the German colonial legacy. In German Cameroon the indigenous slave trade were banned in 1902 and all slaves born after 1902 declared born free; however

2331-619: The economy due to their well-sorted sand and gravel . Sand and gravel are often quarried from these old deltas and used in concrete for highways , buildings, sidewalks, and landscaping. More than 1 billion tons of sand and gravel are produced in the United States alone. Not all sand and gravel quarries are former deltas, but for ones that are, much of the sorting is already done by the power of water. Urban areas and human habitation tend to be located in lowlands near water access for transportation and sanitation . This makes deltas

2394-522: The establishment of a Cameroonian colony, among others. The official beginning of the German "Protectorate of Cameroon" was on 17 August 1884. Gustav Nachtigal had arrived in Duala in July and negotiated a treaty with a number of rulers local to the region around Duala, at that time the center of Germany's trading operations. From there, he would go on to other parts of Cameroon, securing further treaties with

2457-477: The establishment of a colony. For many years prior to the 1880s, Bismarck had resisted the idea of colonial ventures in Africa. This was primarily due to Bismarck's focus on shoring up German interests in Europe itself, especially given the lack of a military infrastructure able to protect colonial interests. Moreover, Germany had no need for the resources that a colony might provide, being largely self sufficient, so

2520-789: The feeding river. Etymologically, the term river delta derives from the triangular shape (Δ) of the uppercase Greek letter delta . In hydrology , the dimensions of a river delta are determined by the balance between the watershed processes that supply sediment and the watershed processes that redistribute, sequester, and export the supplied sediment into the receiving basin. River deltas are important in human civilization , as they are major agricultural production centers and population centers. They can provide coastline defence and can impact drinking water supply. They are also ecologically important, with different species' assemblages depending on their landscape position. On geologic timescales , they are also important carbon sinks . A river delta

2583-414: 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 is deposited as alluvium , which builds up to form the river delta. Over time, this single channel builds a deltaic lobe (such as

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2646-506: The fresh stream feeding the head of tidal propagation. As a result, the tributaries are considered to be "subestuaries". The origin and evolution of a tidal freshwater delta involves processes that are typical of all deltas as well as processes that are unique to the tidal freshwater setting. The combination of processes that create a tidal freshwater delta result in a distinct morphology and unique environmental characteristics. Many tidal freshwater deltas that exist today are directly caused by

2709-466: The geomorphology and ecosystem. Deltas are typically classified according to the main control on deposition, which is a combination of river, wave , and tidal processes, depending on the strength of each. The other two factors that play a major role are landscape position and the grain size distribution of the source sediment entering the delta from the river. Fluvial-dominated deltas are found in areas of low tidal range and low wave energy. Where

2772-406: The lake bottom beyond this steep slope as more gently dipping bottomset beds. Behind the delta front, braided channels deposit the gently dipping beds of the topset on the delta plain. While some authors describe both lacustrine and marine locations of Gilbert deltas, others note that their formation is more characteristic of the freshwater lakes, where it is easier for the river water to mix with

2835-594: The lakewater faster (as opposed to the case of a river falling into the sea or a salt lake, where less dense fresh water brought by the river stays on top longer). Gilbert himself first described this type of delta on Lake Bonneville in 1885. Elsewhere, similar structures occur, for example, at the mouths of several creeks that flow into Okanagan Lake in British Columbia and form prominent peninsulas at Naramata , Summerland , and Peachland . In wave-dominated deltas, wave-driven sediment transport controls

2898-583: The land of the Indians is made by the Indus river no less than is the case with that of Egypt". As a generic term for the landform at the mouth of the river, the word delta is first attested in the English-speaking world in the late 18th century, in the work of Edward Gibbon . River deltas form when a river carrying sediment reaches a body of water, such as a lake, ocean, or a reservoir . When

2961-524: The onset of or changes in historical land use, especially deforestation , intensive agriculture , and urbanization . These ideas are well illustrated by the many tidal freshwater deltas prograding into Chesapeake Bay along the east coastline of the United States. Research has demonstrated that the accumulating sediments in this estuary derive from post-European settlement deforestation, agriculture, and urban development. Other rivers, particularly those on coasts with significant tidal range , do not form

3024-692: The outbreak of World War I , French , Belgian and British troops invaded the German colony in 1914 and fully occupied it during the Kamerun campaign . Following Germany's defeat, the Treaty of Versailles divided the territory into two League of Nations mandates (Class B) under the administration of the United Kingdom and France. French Cameroon and part of British Cameroon reunified in 1961 to form present-day Cameroon . Notably, this did not end German involvement in Cameroon, as many former German plantation owners bought their plantations back in

3087-458: The plantations. This became a problem, as the plantations had more fields than they did workers, so there was a labor shortage. To address this, Puttkamer instituted the "man tithes" mentioned above, in addition to just taking people whenever they conquered new territories or had to put down a rebellion. These people would then be made to do harsh forced labor, with extremely high rates of death. Extreme forms of discipline were practiced too, including

3150-487: The result of this process is the Wax Lake Delta . In both of these cases, depositional processes force redistribution of deposition from areas of high deposition to areas of low deposition. This results in the smoothing of the planform (or map-view) shape of the delta as the channels move across its surface and deposit sediment. Because the sediment is laid down in this fashion, the shape of these deltas approximates

3213-464: The rights of white men and his troops over those of native women, which put him at odds with missionaries in the region. In response to these misdeeds, King Manga Ndumbe Bell of the Duala led a delegation of tribal chieftains to Berlin in 1902 to appeal to the German government in protest of Puttkamer's actions. This delegation was unsuccessful, and three years later Bell made a second attempt, only to be arrested by Puttkamer upon his return and given

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3276-579: The river delta, causing the delta to retreat. For deltas that form further upriver in an estuary, there are complex yet quantifiable linkages between winds, tides, river discharge, and delta water levels. Erosion is also an important control in tide-dominated deltas, such as the Ganges Delta , which may be mainly submarine, with prominent sandbars and ridges. This tends to produce a "dendritic" structure. Tidal deltas behave differently from river-dominated and wave-dominated deltas, which tend to have

3339-414: The river water is nearly equal in density to the basin water, the delta is characterized by homopycnal flow , in which the river water rapidly mixes with basin water and abruptly dumps most of its sediment load. Where the river water has a higher density than basin water, typically from a heavy load of sediment, the delta is characterized by hyperpycnal flow in which the river water hugs the basin bottom as

3402-399: The sediment is never piled up in thick sequences due to the sediment traveling and depositing in deep subduction trenches. At the mouth of a river, the change in flow conditions can cause the river to drop any sediment it is carrying. This sediment deposition can generate a variety of landforms, such as deltas, sand bars, spits, and tie channels. Landforms at the river mouth drastically alter

3465-514: The sediment source. When sediment does not travel far from the source, sediments that build up are coarser grained and more loosely consolidated, therefore making delta formation more difficult. Tectonic activity on active margins causes the formation of river deltas to form closer to the sediment source which may affect channel avulsion , delta lobe switching, and auto cyclicity. Active margin river deltas tend to be much smaller and less abundant but may transport similar amounts of sediment. However,

3528-424: The shape of the delta, and much of the sediment emanating from the river mouth is deflected along the coastline. The relationship between waves and river deltas is quite variable and largely influenced by the deepwater wave regimes of the receiving basin. With a high wave energy near shore and a steeper slope offshore, waves will make river deltas smoother. Waves can also be responsible for carrying sediments away from

3591-598: The slave trade supplied by slave raids in Northern German Cameroon were, in practice, tolerated the entire German colonial period. After Puttkamer left his position, aggressive expansion was less common (though more territory would be added via diplomatic means), and the colony began to focus more on development. With subsidies from the imperial treasury, the colony built two rail lines from the port city of Duala to bring agricultural products to market. The Northern line extended 160-kilometre (99 mi) to

3654-421: The traders began to move further inland. This got bad enough that it necessitated the German government stepping in and officially taking over. From thereon out the administration of the colonies would be at the hands of the German administrators. Regardless, the focus of the colony remained the same: to support the plantation industry and the trade of the German companies. As such, this time saw major expansion in

3717-656: The trailing edges of passive margins due to the majority of large rivers such as the Mississippi , Nile , Amazon , Ganges , Indus , Yangtze , and Yellow River discharging along passive continental margins. This phenomenon is due mainly to three factors: topography , basin area, and basin elevation. Topography along passive margins tend to be more gradual and widespread over a greater area enabling sediment to pile up and accumulate over time to form large river deltas. Topography along active margins tends to be steeper and less widespread, which results in sediments not having

3780-534: Was appointed Governor of Kamerun on 13 August 1895, succeeding Eugen von Zimmerer . During his term, he launched military campaigns against the kingdoms of the Adamawa and Bafut , after both had uprisen against German rule. It was during these campaigns that Puttkamer and his troops committed several atrocities, including forced castrations, fatal floggings, and the kidnapping of young girls to be employed as concubines. In addition, he employed forced labor and favored

3843-554: Was born to an aristocratic family. His father, Robert von Puttkamer , served as Interior Minister of Prussia , while his aunt, Johanna von Puttkamer , was the wife of Otto von Bismarck . Puttkamer studied law at various schools throughout Germany, and as a young man became notorious for engaging in gambling and prostitution. In 1883, he began his diplomatic career working at the German Consulate in Chicago . In 1885, as

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3906-732: Was first coined by Alexander von Humboldt for the middle reaches of the Orinoco River , which he visited in 1800. Other prominent examples include the Inner Niger Delta , Peace–Athabasca Delta , the Sacramento–San Joaquin River Delta , and the Sistan delta of Iran. The Danube has one in the valley on the Slovak–Hungarian border between Bratislava and Iža . In some cases, a river flowing into

3969-593: Was under the informal control of the British Empire throughout the years preceding 1884, with substantial British trading operations as well. Eventually, these companies would begin agitating for royal protection. By 1884, Adolph Woermann , as spokesman for all West African companies, petitioned the imperial foreign office for "protection" by the German Empire. This, among a number of other factors, led to Imperial Chancellor Otto von Bismarck approving

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