The length of the Rhine is conventionally measured in "Rhine-kilometers" (
Rheinkilometer), a scale introduced in 1939 that runs from the 0 km datum at
Old Rhine Bridge in the city of
Konstanz, at the western end of
Lake Constance, to the
Hook of Holland at 1,036.20 km. The river is significantly shortened from its natural course due to a number of canal projects completed in the 19th and 20th centuries. The "total length of the Rhine", including of Lake Constance and the
Alpine Rhine is more difficult to measure objectively; it was cited as by the Dutch Rijkswaterstaat in 2010. Its course is conventionally divided as follows:
Headwaters and sources Sources seen from the Rhine's upstream end The Rhine carries its name without distinctive accessories only from the
confluence of the
Rein Anteriur/Vorderrhein and
Rein Posteriur/Hinterrhein next to
Reichenau in
Tamins. Above this point is the extensive
catchment area of the
headwaters of the Rhine. This area belongs almost exclusively to the
Swiss canton of
Grisons (), ranging from
Saint-Gotthard Massif in the west via one valley lying in the
canton of Ticino and
Sondrio (
Lombardy, Italy) in the south to the
Flüela Pass in the east. The Rhine is one of four major rivers taking their source in the Gotthard region, along with the
Ticino (drainage basin of the
Po),
Rhône and
Reuss (Rhine basin). The
Witenwasserenstock is the
triple watershed between the Rhine, Rhône and Po. Traditionally,
Lake Toma near the
Oberalp Pass in the Gotthard region is seen as the source of the Anterior Rhine and the Rhine as a whole. The Posterior Rhine rises in the
Rheinwald below the
Rheinwaldhorn.
Anterior Rhine and Posterior Rhine (to the left) next to
Reichenau. The source of the river is generally considered north of
Lai da Tuma/Tomasee on
Rein Anteriur/Vorderrhein, although its southern tributary
Rein da Medel is actually longer before its confluence with the Anterior Rhine near
Disentis. :The
Anterior Rhine (, ) springs from
Lai da Tuma/Tomasee, near the
Oberalp Pass and passes the impressive
Ruinaulta formed by the largest visible rock slide in the alps, the
Flims Rockslide. :The
Posterior Rhine (, ) starts from the
Paradies Glacier, near the
Rheinwaldhorn. One of its tributaries, the
Reno di Lei, drains the
Valle di Lei on politically Italian territory. After three main valleys separated by the two gorges,
Roflaschlucht and
Viamala, it reaches
Reichenau in
Tamins. The Anterior Rhine arises from numerous source streams in the upper
Surselva and flows in an easterly direction. One source is
Lai da Tuma () with the
Rein da Tuma, which is usually indicated as source of the Rhine, flowing through it. Into it flow tributaries from the south, some longer, some equal in length, such as the
Rein da Medel, the
Rein da Maighels, and the
Rein da Curnera. The Cadlimo Valley in the
canton of Ticino is drained by the
Reno di Medel, which crosses the
geomorphologic Alpine main ridge from the south. All streams in the source area are partially, sometimes completely, captured and sent to storage reservoirs for the local hydro-electric power plants. The culminating point of the Anterior Rhine's drainage basin is the
Piz Russein of the Tödi massif of the
Glarus Alps at above sea level. It starts with the creek
Aua da Russein (lit.: "Water of the Russein"). In its lower course, the Anterior Rhine flows through a gorge named
Ruinaulta (Flims Rockslide). The whole stretch of the Anterior Rhine to the Alpine Rhine confluence next to Reichenau in Tamins is accompanied by a long-distance hiking trail called
Senda Sursilvana. The Posterior Rhine flows first east-northeast, then north. It flows through the three valleys named
Rheinwald,
Schams and
Domleschg-
Heinzenberg. The valleys are separated by the
Rofla Gorge and
Viamala Gorge. Its sources are located in the
Adula Alps (
Rheinwaldhorn,
Rheinquellhorn, and
Güferhorn). The
Avers Rhine joins from the south. One of its headwaters, the
Reno di Lei (stowed in the
Lago di Lei), is partially located in Italy. Near
Sils the Posterior Rhine is joined by the
Albula, from the east, from the
Albula Pass region. The Albula draws its water mainly from the
Landwasser with the
Dischmabach as the largest source stream, but almost as much from the
Gelgia, which comes down from the
Julier Pass. Numerous larger and smaller tributary rivers bear the name of the
Rhine or equivalent in various
Romansh idioms, including
Rein or
Ragn, including: • Anterior Rhine area:
Rein Anteriur/Vorderrhein,
Rein da Medel,
Rein da Tuma,
Rein da Curnera,
Rein da Maighels,
Rein da Cristallina,
Rein da Nalps,
Rein da Plattas,
Rein da Sumvitg,
Rein da Vigliuts,
Valser Rhine • Posterior Rhine basin:
Rein Posteriur/Hinterrhein,
Reno di Lei,
Madrischer Rhein,
Avers Rhine,
Jufer Rhein • Albula-Landwasser area: In the
Dischma valley, near Davos, far east of the Rhine, there's a place called
Am Rin ("Upon Rhine"). A tributary of the Dischma is called
Riner Tälli. Nearby, on the other side of the
Sertig, is the
Rinerhorn.
Alpine Rhine in Switzerland (left) and
Balzers in
Liechtenstein (right) with the
Gonzen (, left), the
Girrenspitz () in the back, and the Maziferchopf () to the right Next to
Reichenau in
Tamins the
Anterior Rhine and the
Posterior Rhine join and form the Alpine Rhine. The river makes a distinctive turn to the north near
Chur. This section is nearly 86 km long, and descends from a height of 599 meters to 396 meters. It flows through a wide glacial Alpine valley known as the Rhine Valley (). Near
Sargan a natural dam, only a few meters high, prevents it from flowing into the open
Sztal valley and then through
Lake Walen and
Lake Zurich into the
Aare. The Alpine Rhine begins in the westernmost part of the Swiss canton of
Graubünden, and later forms the border between Switzerland to the west and Liechtenstein and later Austria to the east. As an effect of human work, it empties into
Lake Constance on Austrian territory and not on the
border that follows its old natural river bed called
Alter Rhein (). The
mouth of the Rhine into Lake Constance forms an
inland delta. The delta is delimited in the west by the
Alter Rhein and in the east by the modern canalized section of the Alpine Rhine (). Most of the delta is a
nature reserve and
bird sanctuary. It includes the Austrian towns of
Gaißau,
Höchst and
Fußach. The natural Rhine originally branched into at least two arms and formed small islands by precipitating sediments. In the local
Alemannic dialect, the singular is pronounced "Isel" and this is also the local pronunciation of
Esel ("
Donkey"). Many local fields have an official name containing this element. A
regulation of the Rhine was called for, with an upper canal near
Diepoldsau and a lower canal at Fußach, in order to counteract the constant flooding and strong
sedimentation in the western Rhine Delta. The
Dornbirner Ach had to be diverted, too, and it now flows parallel to the canalized Rhine into the lake. Its water has a darker color than the Rhine; the latter's lighter suspended load comes from higher up the mountains. It is expected that the continuous input of sediment into the lake will silt up the lake. This has already happened to the former Lake
Tuggenersee. The cut-off Old Rhine at first formed a
swamp landscape. Later an artificial ditch of about two km was dug. It was made navigable to the Swiss town of
Rheineck.
Lake Constance , is visible, and it includes, in the lower right, the delta of the Alpine Rhine. The northwesterly "finger" (on the top left) is Lake Überlingen
, containing the island of Mainau. Below Lake Überlingen (also in the west) is the smaller Untersee'', containing
Reichenau Island. The Obersee and Untersee are connected by the four kilometers long
Seerhein. On the left the
High Rhine can be seen. Lake Constance () consists of three bodies of water: the
Obersee (), the
Untersee (), and a connecting stretch of the Rhine, called the Seerhein (). The lake is situated in Germany, Switzerland and
Austria near the Alps. Specifically, its shorelines lie in the German states of
Bavaria and
Baden-Württemberg, the Austrian state of
Vorarlberg, and the
Swiss cantons of
Schaffhausen,
St. Gallen and
Thurgau. The Rhine flows into it from the south following the Swiss-Austrian border. It is located at approximately .
Obersee The flow of cold, grey mountain water continues for some distance into the lake. The cold water flows near the surface and at first does not mix with the warmer, green waters of Upper Lake. But then, at the so-called , the Rhine water abruptly falls into the depths because of the greater density of cold water. The flow reappears on the surface at the northern (German) shore of the lake, off the
island of
Lindau. The water then follows the northern shore until
Hagnau am Bodensee. A small fraction of the flow is diverted off the island of
Mainau into Lake Überlingen. Most of the water flows via the
Constance Hopper into the () and Seerhein. Depending on the water level, this flow of the Rhine water is clearly visible along the entire length of the lake. The Rhine carries very large amounts of debris into the lakeover annually. In the mouth region, it is therefore necessary to permanently remove gravel by dredging. The large
sediment loads are partly due to the extensive
land improvements upstream. Three countries border the Obersee, namely Switzerland in the south, Austria in the southeast and the German states of
Bavaria in the northeast and
Baden-Württemberg in the north and northwest.
Seerhein The
Seerhein is only long. It connects the
Obersee with the lower
Untersee. Distance markers along the Rhine measure the distance from the
bridge in the old city center of Konstanz. For most of its length, the Seerhein forms the border between Germany and Switzerland. The exception is the old city center of Konstanz, on the Swiss side of the river. The Seerhein emerged in the last thousands of years, when erosion caused the lake level to be lowered by about . Previously, the two lakes formed a single lake, as the name still suggests.
Untersee Like in the Obersee, the flow the Rhine can be traced in the Untersee. Here, too, the river water is hardly mixed with the lake water. The northern parts of the Untersee (
Lake Zell and
Gnadensee) remain virtually unaffected by the flow. The river traverses the southern, which, in isolation, is sometimes called (). The
Schweizerische Schifffahrtsgesellschaft Untersee und Rhein (URh) offers regular boat trips on Untersee. Besides the
Seerhein, the
Radolfzeller Aach is the main tributary of
Untersee. It adds large amounts of water from the
Danube system to the
Untersee via the
Danube Sinkhole. Reichenau Island was formed at the same time as the Seerhein, when the water level fell to its current level. Lake Untersee is part of the
border between Switzerland and Germany, with Germany on the north bank and Switzerland on the south, except both sides are Swiss in
Stein am Rhein, where the
High Rhine flows out of the lake.
High Rhine (
Switzerland) The High Rhine () begins in
Stein am Rhein at the western end of the Untersee. Now flowing generally westwards, it passes over the
Rhine Falls () below
Schaffhausen before being joinednear
Koblenz in the
canton of Aargauby its major tributary, the
Aare. The Aare more than doubles the Rhine's water discharge, to an average of slightly more than , and provides more than a fifth of the discharge at the Dutch border. The Aare also contains the waters from the summit of
Finsteraarhorn, the highest point of the Rhine
basin. Between
Eglisau and
Basel, the vast majority of its length, the High Rhine forms the
border between Germany and Switzerland. Only for brief distances at its extremities does the river run entirely within Switzerland; at the eastern end it separates the bulk of the
canton of
Schaffhausen and the German
exclave of
Büsingen am Hochrhein on the northern bank from cantons of
Zürich and
Thurgau, while at the western end it bisects the canton of
Basel-Stadt. Here, at the
Rhine knee, the river turns north and leaves Switzerland altogether. The High Rhine is characterized by numerous dams. On the few remaining natural sections, there are still several
rapids. Over its entire course from Lake Constance to the Swiss border at Basel the river descends from . There are passenger boat lines on the lower High Rhine and
between Schaffhausen and Kreuzlingen.
Upper Rhine is Switzerland's gateway to the sea. In the center of Basel, the first major city in the course of the stream, is the
Rhine knee, a major bend, where the overall direction of the Rhine changes from west to north. Here the High Rhine ends. Legally, the Central Bridge is the boundary between High and Upper Rhine. The river now flows north as Upper Rhine through the
Upper Rhine Plain, which is about 300 km long and up to 40 km wide. The most important tributaries in this area are the
Ill below of Strasbourg, the
Neckar in Mannheim and the
Main across from Mainz. In Mainz, the Rhine leaves the Upper Rhine Valley and flows through the Mainz Basin. , in the
Rhine-Neckar industrial area The southern half of the Upper Rhine forms the
border between France (
Alsace) and Germany (Baden-Württemberg). The northern part forms the border between the German states of
Rhineland-Palatinate in the west on the one hand, and
Baden-Württemberg and
Hesse on the other hand, in the east and north. A curiosity of this border line is that the parts of the city of
Mainz on the right bank of the Rhine were given to Hesse by the occupying forces in 1945. The Upper Rhine was a significant cultural landscape in Central Europe already in
antiquity and during the
Middle Ages. Today, the Upper Rhine area hosts many important manufacturing and service industries, particularly in the centers Basel, Strasbourg and Mannheim-Ludwigshafen. Strasbourg is the seat of the
European Parliament, and so one of the three European capitals is located on the Upper Rhine. The Upper Rhine region was changed significantly by a Rhine straightening program in the 19th century. The rate of flow was increased and the ground water level fell significantly. Dead branches were removed by construction workers and the area around the river was made more habitable for humans on
flood plains as the rate of flooding decreased sharply. On the French side, the
Grand Canal d'Alsace was dug, which carries a significant part of the river water, and all of the traffic. In some places, there are large compensation pools, for example, the huge
Bassin de compensation de Plobsheim in Alsace. The Upper Rhine has undergone significant human change since the 19th century. While it was slightly modified during the Roman occupation, it was not until the emergence of engineers such as
Johann Gottfried Tulla that significant modernization efforts changed the shape of the river. Earlier work under
Frederick the Great surrounded efforts to ease shipping and construct dams to serve
coal transportation. Tulla is considered to have domesticated the Upper Rhine, a domestication that served goals such as reducing stagnant
bogs that fostered waterborne diseases, making regions more habitable for human settlement, and reduce high frequency of floods. Not long before Tulla went to work on widening and straightening the river, heavy floods caused significant loss of life. Four diplomatic treaties were signed among German state governments and French regions dealing with the changes proposed along the Rhine, one was "the Treaty for the Rectification of the Rhine flow from Neuberg to Dettenheim"(1817), which surrounded states such as
Bourbon France and the
Bavarian Palatinate. Loops,
oxbows, branches and islands were removed along the Upper Rhine so that there would be uniformity to the river. The engineering of the Rhine was not without protest, farmers and fishermen had grave concerns about valuable fishing areas and farmland being lost. While some areas lost ground, other areas saw swamps and bogs be drained and turned into arable land. Johann Tulla had the goal of shortening and straightening the Upper Rhine. Early engineering projects the Upper Rhine also had issues, with Tulla's project at one part of the river creating rapids, after the Rhine cut down from erosion to sheer rock. Engineering along the Rhine eased flooding and made transportation along the river less cumbersome. These state projects were part of the advanced and technical progress going on in the country alongside the industrial revolution. For the German state, making the river more predictable was to ensure development projects could easily commence. The section of the Upper Rhine downstream from
Mainz is also known as the "Island Rhine". Here a number of
river islands occur, locally known as "Rheinauen".
Middle Rhine to
Rüdesheim, a 2008 video The Rhine is the longest river in Germany. It is here that the Rhine encounters some more of its main tributaries, such as the
Neckar, the
Main and, later, the
Moselle, which contributes an average discharge of more than . Northeastern France drains to the Rhine via the Moselle; smaller rivers drain the
Vosges and
Jura Mountains uplands. Most of
Luxembourg and a very small part of
Belgium also drain to the Rhine via the Moselle. As it approaches the Dutch border, the Rhine has an annual mean discharge of and an average width of . Between
Bingen am Rhein and
Bonn, the
Middle Rhine flows through the
Rhine Gorge, a formation which was created by
erosion. The rate of erosion equaled the
uplift in the region, such that the river was left at about its original level while the surrounding lands raised. The gorge is quite deep and is the stretch of the river which is 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 and many quaint and lovely country villages. The Mainz Basin ends in
Bingen am Rhein; the Rhine continues as "Middle Rhine" into the
Rhine Gorge in the
Rhenish Slate Mountains. In this sections the river falls from 77.4 m above sea level to 50.4 m. On the left, is located the mountain ranges of
Hunsrück and
Eifel, on the right
Taunus and
Westerwald. According to geologists, the characteristic narrow valley form was created by
erosion by the river while the surrounding landscape was lifted (see
water gap). Major tributaries in this section are the
Lahn and the
Moselle. They join the Rhine near
Koblenz, for the right and left respectively. Almost the entire length of the Middle Rhine runs in the German state of Rhineland-Palatinate. The dominant economic sectors in the Middle Rhine area are
viniculture and tourism. The
Rhine Gorge between
Rüdesheim am Rhein and
Koblenz is listed as a UNESCO
World Heritage Site. Near
Sankt Goarshausen, the Rhine flows around the famous rock
Lorelei. With its outstanding architectural monuments, the slopes full of vines, settlements crowded on the narrow river banks and scores of castles lined up along the top of the steep slopes, the Middle Rhine Valley can be considered the epitome of the Rhine romanticism.
Lower Rhine In
Bonn, where the
Sieg flows into the Rhine, the Rhine enters the
North German Plain and turns into the Lower Rhine. The Lower Rhine falls from 50 m to 12 m. The main tributaries on this stretch are the
Ruhr and the
Lippe. Like the Upper Rhine, the Lower Rhine used to
meander until engineering created a solid river bed. Because the levees are some distance from the river, at high tide the Lower Rhine has more room for widening than the Upper Rhine. The Lower Rhine flows through
North Rhine-Westphalia. Its banks are usually heavily populated and industrialized, in particular the
agglomerations Cologne, Düsseldorf and
Ruhr area. Here the Rhine flows through the largest conurbation in Germany, the
Rhine-Ruhr region. One of the most important cities in this region is
Duisburg with the largest
river port in Europe (Duisport). The region downstream of Duisburg is more agricultural. In Wesel, 30 km downstream of Duisburg, is located the western end of the second east–west shipping route, the Wesel-Datteln Canal, which runs parallel to the Lippe. Between
Emmerich and
Cleves the
Emmerich Rhine Bridge, the longest suspension bridge in Germany, crosses the river. Near
Krefeld, the river crosses the
Uerdingen line, the line which separates the areas where
Low German and
High German are spoken. The Rhine River is crossed by several
ferries, including the one between
Bad Honnef and
Rolandseck, where the
Lohfelderfähre district is situated. 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 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 and functions 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 and
brownfields. The Ruhr currently provides the region with drinking water. It contributes to the Rhine. Other rivers in the
Ruhr Area include the
Emscher.
Delta estuary in 1904: light blue old course, dark blue today's course at
Arnhem The Dutch name for Rhine is "Rijn". The Rhine turns west and enters the
Netherlands, where, together with the rivers
Meuse and
Scheldt, it forms the extensive
Rhine-Meuse-Scheldt delta, with the largest
river delta in Europe. Crossing the border into the Netherlands at
Spijk, close to
Nijmegen and
Arnhem, the Rhine is at its widest, although the river then splits into three main
distributaries: the
Waal,
Nederrijn ("Nether Rhine") and
IJssel. From here, the situation becomes more complicated, as the Dutch name
Rijn no longer coincides with the main flow of water. Two-thirds of the water flow volume of the Rhine flows farther west, through the Waal and then, via the
Merwede and
Nieuwe Merwede (
De Biesbosch), 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 of the water flows through the
Pannerdens Kanaal and redistributes in the IJssel and Nederrijn. The IJssel branch carries one ninth of the water flow of the
Rhine north into the
IJsselmeer (a former bay), while the Nederrijn carries approximately two-ninths of the flow west along a route parallel to the Waal. 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 formed the main river Rhine in
Roman times. Though they retained the name, these streams no longer carry water from the Rhine, 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 ("Bent Rhine") 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
Limes Germanicus 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 Rhine-Meuse Delta, the most important
natural region of the
Netherlands begins near
Millingen aan de Rijn, close to the Dutch-German border with the division of the Rhine into
Waal and
Nederrijn. The region between the Dutch-German border and Rotterdam, where the Waal, Lek, and Meuse run more or less parallel, is colloquially known as the "Great Rivers". Since the Rhine contributes most of the water, the shorter term
Rhine Delta is commonly used. However, this name is also used for the
river delta where the Rhine flows into
Lake Constance, so it is clearer to call the larger one
Rhine-Meuse delta, or even
Rhine–Meuse–Scheldt delta, as the Scheldt ends in the same delta. The shape of the Rhine delta is determined by two
bifurcations: first, at
Millingen aan de Rijn, the Rhine splits into
Waal and
Pannerdens Kanaal, which changes its name to
Nederrijn at
Angeren, and second near
Arnhem, the
IJssel branches off from the Nederrijn. This creates three main flows, two of which change names rather often. The largest and southern main branch begins as Waal and continues as
Boven Merwede ("Upper Merwede"),
Beneden Merwede ("Lower Merwede"),
Noord ("the North"),
Nieuwe Maas ("New Meuse"),
Het Scheur ("the Rip") and
Nieuwe Waterweg ("New Waterway"). The middle flow begins as
Nederrijn, then changes into
Lek, then joins the Noord, thereby forming Nieuwe Maas. The northern flow keeps the name IJssel until it flows into Lake
IJsselmeer. Three more flows carry significant amounts of water: the
Nieuwe Merwede ("New Merwede"), which branches off from the southern branch where it changes from Boven to Beneden Merwede; the
Oude Maas ("Old Meuse"), which branches off from the southern branch where it changes from Beneden Merwede into Noord, and
Dordtse Kil, which branches off from Oude Maas. Before the
St. Elizabeth's flood (1421), the
Meuse flowed just south of today's line Merwede-Oude Maas to the North Sea and formed an
archipelago-like estuary with Waal and Lek. This system of numerous bays, estuary-like extended rivers, many islands and constant changes of the coastline, is hard to imagine today. From 1421 to 1904, the Meuse and Waal merged further upstream at
Gorinchem to form
Merwede. For flood protection reasons, the Meuse was separated from the Waal through a lock and diverted into a new outlet called "
Bergse Maas", then
Amer and then flows into the former bay Hollands Diep. The northwestern part of the estuary (around
Hook of Holland), is still called
Maasmond ("Meuse Mouth"), ignoring the fact that it now carries only water from the Rhine. This might explain the confusing naming of the various branches. The hydrography of the current delta is characterized by the delta's main arms, disconnected arms (
Hollandse IJssel,
Linge,
Vecht, etc.) and smaller rivers and streams. Many rivers have been closed ("dammed") and now serve as drainage channels for the numerous
polders. The construction of
Delta Works changed the Delta in the second half of the 20th century fundamentally. Currently Rhine water runs into the sea, or into former marine bays now separated from the sea, in five places, namely at the mouths of the Nieuwe Merwede, Nieuwe Waterway (Nieuwe Maas), Dordtse Kil,
Spui and IJssel. The Rhine-Meuse Delta is a tidal delta, shaped not only by the
sedimentation of the rivers, but also by tidal currents. This meant that high tide formed a serious risk because strong tidal currents could tear huge areas of land into the sea. Before the construction of the Delta Works, tidal influence was palpable up to Nijmegen, and even today, after the regulatory action of the Delta Works, the
tide acts far inland. At the Waal, the most landward tidal influence can be detected between
Brakel and
Zaltbommel. ==Geologic history==