The different states of the Rhine
Thanking
All texts and explanations are taken from the beautiful book “RHIN VIVANT, Histoire du fleuve, des poissons et des hommes” written by Roland Carbiener, honorary professor at the University of Strasbourg, Laurent Schmitt, geographer and hydrogeomorphologist, professor at the University of Strasbourg, and Annick Schnitzler, honorary professor at the University of Lorraine. The commune of Schoenau thanks them for their agreement to use part of their work.
The handover to the commune of a rare copy of this "Carte über den Lauf des Rheins" by Mr Reinhold Hämmerle, surveyor and Rhine history enthusiast, together with his French partner Benoît Sittler, on the occasion of a conference organized in Schoenau by CEN Alsace, was the decisive factor in initiating this permanent exhibition. The commune of Schoenau is very grateful to Mr. Hämmerle for this document and thanks him.
Contents
I - The glacial Rhine (20 000 years ago)
V - The Rhine today and tomorrow
With a 185,000 km2 pond and an average discharge at its mouth of 2,200 m3 per second, the Rhine is Western’s Europe’s leading river. The so-called “Upper Rhine” segment flows between Basel and Bingen (Rhineland-Palatinate) through the “Rhine ditch”, a collapse ditch 300 kilometers long and 30-40 kilometers wide.
I - The glacial Rhine (20 000 years ago)
Stemming from the huge alpin ice cap that covered almost all of present-day Switzerland the Rhine spread its water freely across the Rhine ditch during summer, when some of the ice melted. It formed a gigantic braided bed, with countless arms, banks, islands and terraces from the foothills of the Vosges to those of the Black Forest. The power of the floods transported large qualities of alluvium, constantly modifying the river’s shape.
A water table of extraordinary magnitude
The Upper Rhine alluvial water table was gradually built up during the Quaternary, as a result of the sinking of the Rhine ditch. The deposits, made of Rhine alluvium of all sizes, from localized clays to large pebbles, originating from the alpin pond, the Vosges and the Black Forest cans reach a maximum thickness of 250 meters in Alsace, and cover an area of 3,200 square kilometers.
The water table goes into the cracks at a rate of about one meter per day close to the surface. It is one of the Western Europe’s largest drinking water tank (80 billions cubic meter in the whole Rhine ditch, including 35 billion cubic meter in Alsace).
A major factor to consider when managing water is that most of it is fossil water. Therefore, it can be exploited only on a tiny part of its annual renewal (around 1% per year).
This water table is an extraordinary resource, and we have a duty to protect it and at least maintain its current level. The water table has a consistent temperature of around 11°C around the year. This water table is also bacteriologically pure, free of organic matter and well oxygenated at the surface.
It is important to note that the water table is an essential factor for the Rhine plain landscapes, because its roof is located at a lower depth than the topographic surface (between 0.5 and 2 meters), explaining the presence of wet zone in Grand Ried.
II - The wild Rhine
From the end of the last glaze about 12,000 years ago, the Rhine shaped its flood freely into lots of arms, and that until the massive developments at the beginning of the 19th century. As this map shows, from Basel to Lauterbourg, the Rhin’s profile adapted longitudinally as a response to multiple factors (less water and sediment’s flow due to global warming, the formation of alpine lakes which now contain 60% of sediments, various vertical tectonic movements). As a result, the Rhine has progressively incised on the Basel – Breisach / Marckolsheim section (up to 25 meters!) and the Strasbourg – Lauterberg section (up to 2-3 meters), and tend to maintain or even slightly rise on the Breisach/Marckolsheim – Strasbourg section (between 0.5 to 1 meter) particularly around Rhinau.
Longitudinal sectorization of the Rhine and its alluvial plain (based on studies by L.SCHMITT)
The evolution of the river’s profile, its outline according to the study of old maps of the wild Rhine, and the specificities of the alluvial plain led professor Laurent Schmitt to submit a longitudinal sectorization of the Upper Rhine. The first three sections were clearly distinguishable on the map of the still wild Rhine from 1838.
The first section is between Basel and Breisach/Marckolsheim. The river enters the huge Harth gravel alluvial fan, which mostly extends on the left bank (the west bank). With a steep slope, around 1 meter by kilometer, the rivers splits in countless braids. We call it the “braided section”
The second section is between Breisach/Marckolsheim and Strasbourg. The river’s long profiles, due to the ice age and the wild Rhine’s formation nearly stay consistent, with an elevation of 0.5 to 1 meter near Rhinau. The Rhine expands widely (until 7 kilometers!), the slope lowers (around 0.5 meter per kilometer). This second section was defined as the “braids and anastomoses” section because of the amount of anastomoses there (still visible on an infra map). This Upper Rhine section corresponds, on the French alluvial plain, the gigantic wet zone of Alsace’s Grand Ried.
The third section is located between Strasbourg and Lauterbourg. As the slope diminishes (0.3 to 0.4 meter per kilometer or less), the braids disappear, and the anastomoses’ loops are gradually expanding to reach a meander-type course. This section, characterized by deep, calm, wide “Altwasser”-type side arms, represents the “emerging anastomoses and meanders” section.
The fourth section is located downstream from Lauterbourg, beyond the representation of this map. The very gentle slope (less than 0.1 meter per kilometer) favors the meandering, which become dominants, giving its name to that section. This meanders area goes extends as far as the Rhine schist range, where the river, lined with numerous medieval castles, is known today as the “Romantic Rhine”.
In a nutshell, the wild Rhine presents an exceptional hydro-geomorphological diversity of aquatic habitats. The structure of the whole was organized both longitudinally between Basel and Lauterbourg, and laterally with a unique range of side arms. This richness was the result of the free geomorphological dynamics of the river in its wide alluvial plain, to the rhythm of the pulsating floods. Unfortunately, without an efficient dike system, extreme floods caused considerable damages.
Location of the study area in the Alsatian edge of the Rhine Graben, hydrographic network of the Ello-Rhenan alluvial plain and longitudinal sectorization based on the fluvial style of the Rhine and the paleo-dynamic legacies of the river and the Ill (after CARBIENER, 1969, 1983a; SCHMITT et alii, 2007c).
III - The rectified Rhine
The “rectification” of the Rhine is made by the engineer from Baden Johann Gottfried TULLA (1770-1828).
On this still wild Rhine map of 1838 here, stands the corrected minor bed project according to Tulla’s plan. The map shows the many bends of the river that the rectification would intersect. A close examination of this map reveals that by 1838 some work had already begun, including cutting wide channels (often forward thalwegs) by transverse dikes. In Schoenau, this includes the small transverse dike to the south of the village and the flood level upstream of the “Gestregtenarm”.
A project to stabilize the Rhine had been on the drawing board for a long time, particularly since the annexation of Alsace by Louis XIV, but the project of rectification was agreed between France and the Grand Duchy of Baden on April 5th, 1840, based on the work carried out by the Rhine Rectification Commission. The work, gigantic for its time, given the limited technical resources available, was caried out on the Basel-Lauterbourg section between 1842 and 1876.
The main goals of the Rhine rectification
In addition to establishing borders, the main aim of rectification was to protect the population from flooding. The lateral mobility of the river during floods could erode banks, create new channels and swallow up houses and even entire villages. Another main goal of the rectification was to improve navigation conditions, in particular by creating a towpath. Another target is to develop agriculture and forestry by draining channels and wetlands, thus gaining fertile land. The fight against malaria was also an argument put forward at the time, but this scourge disappeared mainly thanks to the general improvement of living conditions and the use of quinine by the end of the 19th century.
The structure of the rectified Rhine
The rectification work intersected lots of meanders and thalweg loops of the wild Rhine, reducing its length by 32 kilometers on the Basel-Lauterbourg stretch, or 14%, which also increased its slope. The new minor bed was stabilized by two 200 meters long parallel dikes, submersible, paved and reinforced with large rubble stones and fascines. These structures can still be seen on the Schoenau bank in the nature reserve. It is easy to imagine the heavy work required to create this rectified minor bed and the manual maintenance of these structures. During floods, the water flowed over the overflow dike at a rate of around 2,000 cubic meters per second. The Rhine then flooded a large part of its former major bed, on either side of the rectified minor bed, right up to the high-water dikes.
The delimitation of the major bed between high-water dikes
To protect the populations from flooding, Tulla planned a system of unsinkable “high-water dikes”, delimiting a flood expansion field with width varying from 1 to 2 kilometers. During floods, the dense alluvial forest was submerged by flowing silty water, which could rise as high as the rest of the high-water dike. The surveillance services were then on alert, ready to fill any gaps with fascines and stones stored at regular intervals along the dike in shelters. From the top of the dike, in June and July, during the “Cherry Rhine” floods, residents were familiar with the sight of the forest traversed by water laden with silt and fine calcareous sand. For the many fishermen, it was also the promise of abundant and varied future fishing when the waters receded, concentrating the fish in the network of permanent arms.
These dikes are still functional on the German side. On the French side, the 20 kilometers stretch between Sundhouse and Artzenheim is well preserved. Many other dike sections disappeared when the Thine was canalized.
Hydro-geomorphological impacts of rectification
The rectification deeply modified how the Upper Rhine works. Upstream of Breisach/Marckolsheim, an exceptional incision of the rectified minor bed, reaching 7 meters in some places, made the former major bed and lateral branching unreachable to flooding. This incision of the Rhine caused the Istein rock bar to outcrop, making navigation to Basel impossible from 1900 onwards. As the water table deepened with the incision of the minor bed, all the side arms dried up, leading to a drastic decline in fish population and the ruin of several fishermen villages.
Downstream Breisach/Marckolsheim, the minor bed only incised by one meter and the setup of the rectified Rhine guaranteed the maintain of the floodings until the high-water dikes.
Regulation to overcome unexpected impacts of rectification on navigation
After the minor bed rectification, the movement of pebbles and gravel, greatly amplified by incision upstream Breisach/Marckolsheim, made the thalweg very mobile and locally shallow, with large gravel banks. These shoals made navigation increasingly difficult. It was decided to reduce the navigate channel to a minimum width of 75 meters by installing fields of groynes from the banks. These fields of groynes, 2 kilometers long and alternately on either side of the Rhine, created deep trenches where powerful waves were located. In Schoenau, the good swimmers of the time were aware of this danger while crossing the river and experienced some major scares. The groynes technique was designed to allow the river to be self-cleaning, creating a single navigation channel at least 2 meters deep. This work began downstream in 1906 and was completed in 1939. However, the maintenance of these groynes lasted until the pipeline was built, with the installation of 8 to 10 meters by 0.9 meters gabions or “sausages”, made from sturdy wire mesh filled with rocks and pebbles, one on top of the other. Here too swimmers avoided ending up in the groynes and climbing back up to the bank, because the gabion mesh was rusting and presented high risk of injuries.
All the rectification and regulation work created numerous jobs in the near Rhine villages. In Schoenau too, several families were living of those Rhine trade, handled by the navigation and Rhine service (maintenance of the river banks, the high-water dikes, the groynes, the bridges).
IV - The canalised Rhine
Goals, structure, and hydro-geomorphological impacts of canalization
With the regulation, the navigation’s conditions widely increased, despite the Istein bar appearing. As a result, Switzerland lost its waterway access to the North Sea, limiting its industrial development. At the beginning of the 20th century, the solution of a local bypass around Kembs, then to Strasbourg via the Grand Canal d’Alsace was emerging. The industrials from Mulhouse, leaded by René Koechlon, would add to it a new hydroelectric goal. All these measures were included in the provisions of the 1919 Treaty of Versailles, awarding all hydroelectric power of the Upper Rhine to France.
160 kilometers of pipeline and 10 hydroelectric factories
The Grand Canal d’Alsace was to include eight hydroelectric factories along the 120-kilometer length between Kembs and Strasbourg, along with pairs of locks. The first factory, at Kembs (1932), was the only one built before the Second World War. At the upstream end of the scheme, a diversion dam has been built on the old Rhine, diverting most of the flow into the Grand Canal d’Alsace, up to a technical threshold of 1,400 cubic meters per second. It is only during floods that the flow if the Old Rhine increases.
The next factories, also located on the Grand Canal d’Alsace, downstream Kembs, were Ottmarsheim (1956) and Volgelgrun (1959). Factory chutes are 12 to 14 meters high. The Old Rhine is one of the longest sections of short-circuited major rivers in the world. Since 1965, the downstream end of the river has been equipped with an “agricultural dam”, the Breisach dam, with a head of 5.5 meters to raise the water table.
For prevent sinking of the water table, but also to give Germany access to the access to the waterway, the downstream continuation of the pipeline was downstream using the "festons" principle. Each feston, from 5 to 12 km long, includes a hydroelectric factory (Marckolsheim in 1960, Rhinau in 1964, Gerstheim in 1967 and Strasbourg in 1971), a diversion dam, as at Schoenau, a headrace reach and a tailrace reach, both canalized, and between which are placed the hydroelectric factory, the pair of locks, as well as a "short" section of short-circuited Old Rhine. The height of the factory falls is around 13m. Between each festoon is a few kilometers of channelized Rhine bed, as between Marckolsheim and the Schoenau dam, allowing the water table to be raised and giving the right bank access to the waterway. The spaces between the canalised riverbed and the Old Rhine are new artificial islands in the Rhine, with varying degrees of flooding. This is the case for the national nature reserve between Schoenau and Rhinau. Agricultural" weirs also dam the Old Rhine to compensate for the lowering of the water table (3 weirs between Schoenau and Rhinau). However, these developments have greatly disrupted the alluvial function of the river, and siltation in front of these weirs is significant.
Downstream of Strasbourg, the continuation of the pipeline was hardly motivated by the production of additional electricity, as the reduction in gradient made it less profitable. However, it was decided to continue with the canalisation in order to stop the river sinking due to bottom erosion, which resumed downstream of the Strasbourg feston, as it had done in the past after the construction of each new factory. Furthermore, as Franco-German relations improved, the principle of festons was abandoned, and France and Germany agreed to build the Gambsheim factory in 1974, and the Iffezheim factory in 1977, in the riverbed itself, whose banks were not concreted along this stretch. The falls are around 12 m high.
The ten hydroelectric factories along the Franco-German line produce an average of 8.7 billion kWh/year, or around two-thirds of Alsace's electricity needs. In terms of navigation, the locks enable 25 million tonnes of goods to be transported by water each year in Strasbourg, compared with around 11 million tonnes in Basel.
Impact of river functioning
The canalized reaches, whose banks were concreted over and whose bottoms are essentially composed of pebbles and gravel, except locally in the region of factories and locks, cover a total area of around 4,500 ha, including dykes and roads. Nearly 450 ha of the Schoenau municipal area was affected (dikes, canalization and Rhine island).
Along the 160 km of canalised waterway, the long profile of the water line is like a staircase, with the steps corresponding to the water reservoirs upstream of the dams and hydroelectric plants, which act as risers. Artificially maintained water levels are no longer correlated with flow. Speeds are relatively slow, at less than 1 meter per second, excluding floods. Unfortunately, the dykes also make the river inaccessible to the public eye, which helps to break the many links with the river.
The pipeline has interrupted the transit of rough sediments (rough sands, gravels, pebbles), which are transported to the bottom of riverbeds. The small inflows from tributaries are deposited upstream of hydroelectric factories and diversion dams, such as the Schoenau dam. The finer elements (medium and fine sands, silts and clays) can no longer fertilize the alluvial forest, which can no longer be flooded. These fine sediments settle to the bottom of the river and, unfortunately, act as pollutant fixers and accumulators.
All these modifications have had a major impact on the aquatic environment, with fish populations declining sharply. In hydrological terms, the major impact of the pipeline is the amputation of 130km² of flood-prone areas. As these areas were previously used for temporary flood storage, the pipeline increased the risk of flooding by shifting it downstream.
V - The Rhine today and tomorrow
Correcting hydrological errors in the pipeline
A Franco-German agreement was signed in 1982 to eliminate the negative hydrological effects of the pipeline and, in particular, to restore flood control capacity. The aim of this agreement is to reinforce the safety of riverside populations downstream of the canalized Rhine against the largest floods (200 years), as was the case prior to the canalization.
Several Franco-German measures were taken:
- On the left bank: cessation of turbines at the EDF plants between Basel and Strasbourg in order to transfer water from the canalised Rhine to the sections of the Old Rhine, creation of the Erstein and Moder polders.
- On the right bank: adaptation of the Strasbourg-Kehl and Breisach agricultural dams to store more water during flood periods, development of 16 polders, including those at Burkheim and Wyhl-Weisweil, and lowering of the alluvial plain on the right bank along 43 km of the Old Rhine upstream of Breisach. All these works should be completed by 2038.
The French and German polders also have an ecological restoration vocation, as do the German riverbank embankments, although flood protection objectives predominate.
Half a century of protection and restoration
A wide range of regulatory tools have been put in place at international level, and actions between states are discussed and steered at the level of the International Commission for the Protection of the Rhine (ICPR). The current "Rhine 2040" program focuses in particular on:
- To re-establish longitudinal fish continuity on the Rhine and its tributaries so that migratory fish can reach the natural waterfalls of the Rhine at Schaffhausen and the Swiss tributaries. Construction of the various fish passes at the hydroelectric factories is underway.
- Increase the surface area of the major riverbed by 200 km², reconnect 100 side arms and diversify the morphology of 400 km of riverbanks.
- Improve water quality, particularly with regard to micro-pollutants
- And to strengthen adaptation to climate change.
The main protection measures implemented along the Rhine since the 1970s are:
- The creation of 8 national nature reserves between 1982 and 2020
- The emergence of a plan to protect the Rhine Forest, the classification of wooded areas as protection forests, following the Marckolsheim agreements in 1990.
- Numerous Natura 2000 sites have been listed, two biotope protection decrees have been issued, and three biological reserves have been created.
Alongside the Petite Camargue Alsacienne and the City of Strasbourg, the “Conservatoire d'Espaces Naturels d'Alsace” (CEN Alsace) manages the largest number of reserves (four).
The "Ill-Nappe-Rhin" water development and management plan approved in 2004 aims to "guarantee the quality of groundwater, restore the quality of watercourses by sustainably satisfying uses, ensure overall consistency between the objectives of flood protection and the preservation of wetlands" and restore the arms of the Rhine.
On December 5, 2019, the French managers of the Rhine drew up and signed an ambitious action program: the "Rhin Vivant" plan. This 10-year program is supported by the French government, the Grand Est region, the Rhine-Meuse Water Agency and the French Biodiversity Office. The ambition is to restore the functionality, biodiversity, and landscapes of Rhine environments, with associated ecosystem services such as bio climatization during heatwaves, to strengthen the adaptation of environments to climate change, and to re-establish social links between the population and the river". It is in this context that the study for the restoration of the forest and alluvial massif from Marckolsheim to Schoenau was launched.