The Rhine (Rhein; Rijn; Rhin; Reno; Rain; Rhenus) is one of the longest and most important rivers in Europe at 1,320 kilometres (820 mi), with an average discharge of more than 2,000 cubic meters per second. The name of the Rhine comes from the archaic German Rhine, which in turn comes from Middle High German: Rin, from the Proto-Indo-European root *reie- ("to flow"). The Reno River in Italy shares the same etymology.
The Rhine and the Danube formed most of the northern inland frontier of the Roman Empire, and since those days the Rhine has been a vital navigable waterway, carrying trade and goods deep inland. It has also served as a defensive feature, and has been the basis for regional and international borders. The many castles and prehistoric fortifications along the Rhine testify to its importance as a waterway. River traffic could be stopped at these locations, usually for the purpose of collecting tolls, by the state controlling that portion of the river.
Between Bingen and Bonn, the Middle Rhine flows through the Rhine Gorge, a formation created by erosion, which happened at about the same rate as an uplift in the region, leaving the river at about its original level, and the surrounding lands raised. This gorge is quite deep, and is the stretch of the river known for its many castles and vineyards. It is a UNESCO World Heritage Site (2002) and known as "the romantic Rhine" with more than 40 castles and fortresses from the Middle Ages (see links) and many quaint and lovely wine villages.
Until the early 1980s industry was a major source of water pollution. Although many plants and factories can be found along the Rhine up into Switzerland, it is along the Lower Rhine in the Ruhr area that the bulk of them are concentrated, as the river passes the major cities of Cologne, Düsseldorf, and Duisburg. Duisburg is the home of Europe's largest inland port, functioning as a hub to the sea ports of Rotterdam, Antwerp and Amsterdam. The Ruhr, which joins the Rhine in Duisburg, is nowadays a clean river, thanks to a combination of stricter environmental controls, a transition from heavy industry to light industry, and cleanup measures such as the reforestation of slag heaps and brownfields. The Ruhr currently provides the region with drinking water. It contributes 70 cubic meters per second to the Rhine. Other rivers in the Ruhr area, above all the Emscher, still carry a considerable degree of pollution.
From here the situation becomes more complicated, as the Dutch name "Rijn" no longer coincides with the main flow of water. Most of the Rhine water (two thirds) flows farther west through the Waal and then via the Merwede and Nieuwe Merwede (Biesbosch) and, merging with the Meuse, through the Hollands Diep and Haringvliet estuaries into the North Sea. The Beneden Merwede branches off near Hardinxveld-Giessendam and continues as the Noord, to join the Lek near the village of Kinderdijk to form the Nieuwe Maas, then flows past Rotterdam and continues via Het Scheur and the Nieuwe Waterweg to the North Sea. The Oude Maas branches off near Dordrecht, farther down rejoining the Nieuwe Maas to form Het Scheur.
The other third portion of the water flows through the Pannerdens Kanaal and redistributes in the IJssel and Nederrijn. The IJssel branch carries one ninth of the water volume north into the IJsselmeer (a former bay), while the Nederrijn flows west parallel to the Waal and carries approximately two ninths of the flow. However, at Wijk bij Duurstede the Nederrijn changes its name and becomes the Lek. It flows farther west to rejoin the Noord into the Nieuwe Maas and to the North Sea.
The name "Rijn" from here on is used only for smaller streams farther to the north which together once formed the main river Rhine in Roman times. Though they retained the name, these streams do not carry water from the Rhine anymore, but are used for draining the surrounding land and polders. From Wijk bij Duurstede, the old north branch of the Rhine is called Kromme Rijn ("Crooked Rhine") and past Utrecht, first Leidse Rijn ("Rhine of Leiden") and then Oude Rijn ("Old Rhine"). The latter flows west into a sluice at Katwijk, where its waters can be discharged into the North Sea. This branch once formed the line along which the Upper Germanic limes were built. During periods of lower sea levels within the various ice ages, the Rhine took a left turn, creating the Channel River, the course of which now lies below the English Channel.
The bridges at Huningue, Rastatt, Rüdesheim (Hindenburgbrücke) and Remagen (Ludendorffbrücke) were built for strategic military reasons only, in order to allow the Imperial German Army (and later the Wehrmacht) to quickly transport forces by rail to Germany's western border in the event of a war with France. Unlike other bridges built for the same purpose (like the ones at Koblenz or Cologne), these bridges were of almost no use in peacetime and thus were never rebuild after their destruction during the last months of World War 2 (except for the one at Rastatt, which was used to supply units of the French Army stationed in the area).
In southern Europe, the stage was set in the Triassic Period of the Mesozoic Era, with the opening of the Tethys Sea between the Eurasian and African plates, between about 240 MBP and 220 MBP. The present Mediterranean descends from this somewhat larger Tethys sea. At about 180 MBP, in the Jurassic Period, the two plates reversed direction and began to compress the Tethys floor, causing it to be subducted under Eurasia and pushing up the edge of the latter plate in the Alpine Orogeny of the Oligocene and Miocene Periods. Several microplates were caught in the squeeze and rotated or were pushed laterally, generating the individual features of Mediterranean geography: Iberia pushed up the Pyrenees; Italy the Alps, and Anatolia, moving west, the mountains of Greece and the islands. The compression and orogeny continue today, as shown by the ongoing raising of the mountains a small amount each year and the active volcanoes.
In northern Europe, the North Sea Basin had formed during the Triassic and Jurassic period, and continued to be a sediment receiving basin since. In between the zone of Alpine Orogeny and North Sea Basin subsidence, remained highlands resulting from an earlier orogeny (Variscan), such as the Ardennes, Eifel, and Vosges.
From the Eocene onwards, the ongoing Alpine Orogeny caused a N-S rift system to develop in this zone. The main elements of this rift are the Upper Rhine Graben in southeast Germany/eastern France and the Lower Rhine Embayment in northwest Germany/southeast Netherlands. By the time of the Miocene, a river system had developed in the Upper Rhine Graben, that continued northward and is considered the first Rhine river. At that time it did not yet carry discharge from the Alps: instead the watersheds of Rhone and Danube drained the northern flanks of the Alps.
Through stream capture, the Rhine extended its watershed southward. By the Pliocene period, the Rhine had captured streams down to the Vosges mountains, including the Mosel, the Main, and the Neckar. The northern Alps were drained by the Rhône then. By the early Pleistocene period, the Rhine had captured most of its current Alpine watershed from the Rhône, including the Aare. Since that time, the Rhine has added the watershed above Lake Constance (Vorderrhein, Hinterrhein, Alpenrhein; captured from the Rhône), the upper reaches of the Main (beyond Schweinfurt), and the Vosges mountains (captured from the Meuse) to its watershed.
The last glacial ran from (~74,000 BP = Before Present) until the end of the Pleistocene (~11,600 BP). In northwest Europe, it saw two very cold phases, peaking around 70,000 BP and around 29,000-24,000 BP. The last phase slightly predates the global last ice age maximum (Last Glacial Maximum). During this time the lower Rhine flowed roughly west through the Netherlands and extended to the southwest, through the English Channel, and finally to the Atlantic Ocean. The English and Irish Channels, and most of the North Sea were dry land, mainly because sea level was approximately 120 m lower than today.
Most of the Rhine's current course was not under the ice during the last Ice Age, although its source must then have been a glacier. A tundra with Ice Age flora and fauna stretched across middle Europe from Asia to the Atlantic Ocean. Such was the case during the Last Glacial Maximum, ca. 22,000-14,000 yr BP, when ice-sheets covered Scandinavia and the Baltic, Scotland and the Alps, but left the space between as open tundra. The loess, or wind-blown dust over that tundra settled in and around the Rhine Valley, contributing to its current agricultural usefulness.
With globally shrinking ice-cover, ocean water levels rose and the English Channel and North Sea re-inundated. Meltwater adding to the ocean and land subsidence drowned the former coasts of Europe (transgression). About 11000 yr ago, the Rhine estuary was in the Dover Strait. There remained some dry land in the southern North Sea, connecting mainland Europe to Britain. About 9000 yr ago, that last divide was overtopped / dissected. These events were well within the residence of man.
Since 7500 yr ago, a situation with tides and currents very similar to present has existed. Rates of sea-level rise had dropped so far that natural sedimentation by the Rhine and coastal processes together could compensate the transgression by the sea: in the last 7000 year the coast line was roughly at the same location. In the southern North Sea, due to ongoing tectonic subsidence, the sea-level is still rising, at the rate of about 1-3 cm per century (1 meter in last 3000 years).
About 7000-5000 BP a general warming encouraged migration up the Danube and down the Rhine by peoples to the east, perhaps encouraged by the sudden massive expansion of the Black Sea as the Mediterranean burst into it through the Bosphorus about 7500 BP.
Since ~3000 yr BP (= years Before Present) human impact is seen in the delta. As a result of increasing land clearance (Bronze Age agriculture) in the upland areas (central Germany), the sediment load of the Rhine River has strongly increased (Hoffmann et al. 2007) and delta growth has sped up (Gouw & Erkens, 2007). This caused increased flooding and sedimentation, and ended peat formation in the delta. The shifting of river channels to new locations on the floodplain (termed avulsion) was the main process distributing sediment across the subrecent delta. Over the past 6000 years, approximately 80 avulsions have occurred (documented by Berendsen & Stouthamer, 2001). Direct human impact in the delta started with peat mining for salt and fuel from Roman times onward. This was followed by embankment of the major distributaries and damming of minor distributaries which took place in the 11-13th century AD. Thereafter, canals were dug, bends were short cut and groynes were built to prevent the river's channels from migrating or silting up.
At present, the branches Waal and Nederrijn-Lek discharge to the North Sea through the former Meuse estuary near Rotterdam. The river IJssel branch flows to the north and enters the IJssel Lake (formerly the Zuiderzee brackish lagoon, since 1932 a freshwater lake). The discharge of the Rhine is divided among three branches: the River Waal (6/9 of total discharge), the River Nederrijn - Lek (2/9 of total discharge) and the River IJssel (1/9 of total discharge). This discharge distribution has been maintained since 1709 by river engineering works (digging of Pannerdens canal) and since the 20th century with the help of weirs in the Nederrijn river.
Neanderthal sites are denser to the south, where open forest prevailed and the limestone terrain offered more caves as dwelling. The Rhine ran through an open tundra, where Neanderthals hunted big game, such as the rhinoceros and the woolly mammoth. Accordingly, open air Mousterian sites have been discovered in and around the Rhine valley.
The human history of the Rhine begins with the writers of the late Roman Republic and early Roman Empire. Nearly all the classical sources mention the Rhine, and the name is always the same: Rhenus in Latin, Greek Rhenos. The Romans viewed the Rhine as the outermost border of civilization and reason, beyond which were mythical creatures and the wild Germanic tribesmen, not far themselves from being beasts of the wilderness they inhabited. As it was a wilderness, the Romans were eager to explore it. This view is typified by Res Gestae Divi Augusti, a long public inscription of Augustus in which he (or his ghost writer) boasts of his exploits, including sending an expeditionary fleet north of the Rheinmouth to Old Saxony and Jutland, which he claims no Roman had ever done.
Throughout the long history of Rome, the Rhine was considered the border between Gaul or the Celts and the Germanic peoples, although it should be noted that the historical ethnonyms do not carry their modern ethno-linguistic definitions. Typical of this point of view is a quote from Maurus Servius Honoratus, Commentary on the Aeneid of Vergil (On Book 8 Line 727):
The Rhine in the earlier sources was always a Gallic river.
As the Roman Empire grew, the Romans found it necessary to station troops along the Rhine. They kept two army groups there (exercitus), the inferior, or "lower", and the superior, or "upper", which is the first distinction between upper Germania and lower Germania. It originally probably only meant upstream and downstream, the Niederrhein and Oberrhein regions of the map included with this article.
The Romans kept eight legions in five bases along the Rhine. The actual number of legions present at any base or in all depended on whether a state or threat of war existed. Between about 14 AD and 180 AD the assignment of legions was as follows. For the army of Germania Inferior, two legions at Vetera (Xanten): I Germanica and XX Valeria (Pannonian troops); two legions at oppidum Ubiorum ("town of the Ubii"), which was renamed to Colonia Agrippina, descending to Cologne. The legions were V Alaudae, a Celtic legion recruited from Gallia Transalpina, and XXI, possibly a Galatian legion from the other side of the empire.
For the army of Germania superior, one legion, II Augusta, at Argentoratum (Strasbourg), and one, XIII Gemina, at Vindonissa (Windisch). Vespasian had commanded II Augusta before his promotion to imperator. In addition were a double legion, XIV and XVI, at Moguntiacum (Mainz).
The two originally military districts of Germania Inferior and Germania Superior came to influence the surrounding tribes, who later respected the distinction in their alliances and confederations. For example, the upper Germanic peoples combined into the Alemanni. For a time the Rhine ceased to be a border when the Franks crossed the river and occupied Roman-dominated Celtic Gaul as far as Paris.
The first urban settlement on the grounds of what today is the centre of Cologne along the Rhine was Oppidum Ubiorum, which was founded in 38 BC by the Ubii, a Germanic tribe. Cologne became acknowledged as a city by the Romans in 50 AD by the name of Colonia Claudia Ara Agrippinensium. Considerable Roman remains can be found in contemporary Cologne, especially near the wharf area along the Rhine, where a notable discovery of a 1900 year old Roman boat was made on the Rhine banks in late 2007.
Subsequently language changes began to play a major political role. West Germanic dissimilated into Low Saxon, Low Franconian languages and High German languages roughly along the old lines. Perhaps it had been doing so all along. Charlemagne united all the Franks in the Holy Roman Empire, but he did not rule over a people of uniform language. After his death the empire split more or less along language lines, with the Low Franconian being spoken in the Netherlands and the Low Saxon and High German in what became Germany. The Romanized Franks became the French. The Rhine once again became a political border.
The Rhine as border has been and is a mystical and political symbol. German authors and composers have written reams about it. During World War II, it was still considered the sacred border of Germany, and was still a defensive barrier. The Germans fought especially hard to defend it.
The Rhine is closely linked to many important historical events — particularly military ones — as well as myths. For example: