An Environmental History of the First Attempts to Straighten the River Inn in Tyrol (1745–1792)

Abstract

The first systematic attempts to straighten the River Inn in Tyrol for shipping and land reclamation date back to the middle of the 18th century. A dedicated hydraulic engineering authority—the so-called Main Ark Inspection—was established to realize this challenging task. The one-man authority was unable to straighten the Alpine river through the period of its existence up to 1792. The reasons for this were by no means related to a lack of technical resources and knowledge. On the contrary, a micro- and environmental-historical analysis of the attempts to straighten the River Inn highlights the complexity of the causes, which were mutually reinforcing and multifactorial. In this paper, four key causes are examined in more detail: (1) the social organization of water engineering, (2) social conflicts between riparian communities among themselves and with the hydraulic engineering authority, (3) conflicts between Tyrol and Bavaria at the wet border downstream of Kufstein, and (4) increased bedload discharge into the main river by tributaries. To illustrate the causes mentioned above, historical river maps are analyzed in great detail, drawing on contemporaneous written sources. The approach thereby highlights the overall complexity of pre-modern hydraulic engineering in all its facets, be they social, technical, natural, administrative, or organizational. To conclude, the results of this environmental history research are embedded and discussed in the context of integrated river management in the Anthropocene.

1. Introduction

The River Inn is the most significant river in the eastern Alps, with a total length of 517 km. Its hydrological catchment area extends over 26,068 km², encompassing the source at the Lunghin Pass (2484 m) in the canton of Grisons (Switzerland) to its confluence with the Danube at Passau in Bavaria (Germany) (Figure 1). In the Alpine region, the Inn has a length of 373 km and a catchment area of 20,234 km², making it the longest river in the Alps. The Inn flows through Tyrol from west to east (Figure 2a). Today, it has a free-flowing section of 150 km between Imst and Kirchbichl in Tyrol. As a tributary of the Danube, the River Inn loses its name at Passau, even though it carries a greater volume of water at the confluence with the Danube [1].

In pre-modern times, the raging Alpine River Inn had been extensively used for shipping from Hall in Tyrol to further downstream. Use of the Inn for waterborne transport declined sharply in the first half of the 18th century. Due to strong fluvial dynamics and seasonally fluctuating water levels, the necessary embankments—the so-called “arks”—required costly annual maintenance work and new construction. In Tyrolean dialect, ark (“Arche”) referred to river embankments (Figure 3). The word is derived from the Latin “arca” (box) and refers to the box-like shape of these massive embankments [6] (p. 283). At the same time, each year, floods were destroying more and more farmland in the Inn valley, which was in danger of deteriorating to marshland. To better coordinate hydraulic engineering works on the Inn and straighten the Alpine river, a new Main Ark Inspection authority was established in 1745. The Court Chambers in Vienna and Innsbruck expected that straightening the river would not only significantly reduce the cost of hydraulic engineering, but also improve navigation. In 1745, a boat train from Kufstein to Hall took eightdays, up to 60 horses, and cost 800 guilders in total. Straightening the river meant reducing the journey to five days and the cost to 500 guilders, according to the designated Main Ark Inspector, Engineer-Lieutenant Franz Anton Rangger (1723–1777) [7]. In addition, he estimated that, in total, 450 hectares of so-called “barren ground”, extensive floodplains along the river, could be “conquered” and cultivated. Agricultural land had been scarce in the mountainous Tyrol and the province had always been dependent on food imports. To reclaim this fallow land was therefore seen as an important step towards self-sufficiency.

The research question deals with the failure of the first attempts to straighten the river as intended by the authorities in the 18th century. This question is even more pressing as neither hydraulic engineering resources nor hydraulic engineering knowledge were “insufficient” or imperfect at that time, as is sometimes anachronistically claimed. This can clearly be demonstrated by the successful straightening of meandering river bends or other river sections (see Section 4), as well as by contemporaneous hydraulic engineering treatises on Alpine rivers and their practical relevance [10,11].

The central thesis of this paper is that a monocausal explanation falls far short of adequately addressing the issue, as an environmental-historical reconstruction of the reasons for the failure reveals. Rather, many factors were involved in the Main Ark Inspection authority failing to realize the straightening of the Inn in the second half of the 18th century. All in all, four central causes of this failure can be identified. However, upon closer consideration, it becomes clear that such a systematization quickly reveals itself to be a historiographical construct. This is because, in practice, the causes often overlapped and, in some cases, reinforced each other.

In the first place, it is important to highlight (1) the multi-level administrative structure under the Habsburg Monarchy and its ever-uncertain financial basis. Due to the traditional social organization of hydraulic engineering, in some cases the subjects along the river were obliged to maintain the hydraulic engineering infrastructure. Lacking interest and resources, these communities (2) embanked the river contrary to the approach of the Main Ark Inspector by using so-called “throwing arks”, which were built perpendicular to the river banks. This was the reason for conflicts between individual municipalities and between these municipalities and the hydraulic engineering authority. The same applies (3) to conflicts along the water border between the County of Tyrol and the Electorate of Bavaria below Kufstein. All of these social causes were accompanied and exacerbated by the natural dynamics of an Alpine river, the Inn. To guarantee an integrated approach to river management, environmental historians must consider the entire hydrological catchment area in their river research, as emphasized by Martin Schmid [12]. Taking this into account, (4) another obstacle to straightening the river was the sedimentary load of the tributaries, all of which were highly dynamic Alpine torrents. The sedimentary input resulted in a significant rise in the riverbed, resulting in more frequent and severe flooding. The various causes of failure mentioned above are further analyzed in the four corresponding sections below.

2. State of the Art, Methods, and Historical Sources

The interdisciplinary field of river science is primarily based on natural science disciplines such as geology, hydrology, and geomorphology [13,14,15]. At the same time, the social sciences provide equally important insights into contemporary societal interactions with rivers. However, the results of the discipline of environmental history are also an integral part of river science. “By combining documentary evidence, analysis, and narrative, it reconstructs aspects of past fluvial dynamics that the tools of earth scientists cannot always detect” [16] (p. 29). The role of history in integrated river management is particularly evident in interdisciplinary research settings such as the Institute of Social Ecology in Vienna [17,18,19] or in the new Priority Program 2361 “On the way to the fluvial Anthroposphere” [20]. The numerous publications on the environmental history of rivers in recent years are also striking evidence of this [21,22,23,24,25,26]. With regard to the wide range of topics and studies in environmental-historical river research prior to 2017, two review essays are still highly recommended [27,28].

The methodological approach of this paper is based on environmental and regional history. The concept of “socio-natural sites” (“sozionaturale Schauplätze”) provides a useful framework for environmental history research [29]. In contrast, Patrick Kupper emphasizes the term “socio-natural relations” (“sozionaturale Verhältnisse”). He argues that the term “relations” is more dynamic than “sites” [30] (pp. 23–24). Both concepts focus on analyzing changes in the interactions between natural systems and humans, which underlines their applicability to river history. While this essay owes numerous references to both concepts, this is not the appropriate place for a methodological comparison of the two, and thus their use is deliberately avoided in this article. Small-scale analysis of particular places and regions is well-suited to environmental history [31] (pp. 83–93), because specific environmental conditions have very different effects even at small scales, and social reactions to them also vary both temporally and spatially. These empirical insights ultimately serve as the basis for narratives of global environmental history, which also consist of individual case studies, given that local causes can have global effects [32,33].

The historical source material comes from the Tyrolean Regional Archives in Innsbruck, the Austrian State Archives in Vienna, and the Bavarian Main State Archives in Munich. The extensive archival material allows a micro-historical observation. In line with the methodological approach proposed by the Italian micro-historian Giovanni Levi, the central principle guiding this study is that environmental historians of rivers do not study rivers, they study in and alongside rivers [34] (p. 96). The micro-historical enlargement of the scale, that is, a reduction in the study area [35,36,37,38], makes it possible to reconstruct both the actual shape of and the changes to the riverscape and the hydraulic engineering measures on the River Inn. In this study, historical river maps are used and combined with contemporaneous written sources to highlight the problems perceived by the hydraulic engineering experts on the river [39,40,41,42,43]. The proposed options for resolving these problems and the decision-making process taking place between the Main Ark Inspector, the regional authorities in Innsbruck, and the central authorities in Vienna can be reconstructed as if under a microscope. This provides exciting comparative insights into different problems of scale [44,45,46].

It is only through this sometimes laborious and time-consuming approach that the complexity of pre-modern hydraulic engineering in all its different facets—be they social, technical, natural, administrative, organizational, or religious—can be adequately represented. This approach also makes it possible to highlight the individual logics and interests of the actors and local, regional, and central authorities involved. The primary focus of this study is on the interaction between the river and anthropogenic interventions.

3. Administration, Social Organization, and Financing of Hydraulic Engineering of the River Inn in Tyrol

The social organization of hydraulic engineering included separate administrations responsible for the financing and maintenance of river embankments in Tyrol. On the one hand, the central government in Vienna and the Ark Building Masters, and on the other, the Privy Council in Innsbruck and local communities, were responsible for the financing and maintenance of certain river embankments. According to the state-centered perspective of hydraulic engineering, the local communities were classified as “particulars” and were either monasteries, municipalities, or private individuals. This paper will refer to arks maintained by the government as “sovereign arks” and arks maintained by local communities will be referred to as “particular arks”.

The Main Ark Inspector examined the entire hydraulic engineering infrastructure for the Inn twice a year, in autumn and in spring. The entire organization and all administrative procedures of the Main Ark Inspection authority were precisely aligned with and adapted to the rivers’ seasonally significant fluctuating discharge regime. This administrative adaptation applied to the management of all natural resources [47]. The inspector spent approximately six weeks at the river banks on each occasion. In the case of sovereign arks, an Ark Building Master was present for the inspection and subsequently carried out the construction ordered. The local authorities and local communities were expected to be present at inspections of the particular arks, although they were notoriously absent in relation to their enthusiasm for the office.

While on “visitation”, the Main Ark Inspector checked the damage to the arks caused by floods in summer and autumn. On this basis, he made proposals for repairs and completely new embankments. Some of these proposals are described in detail in the reports. The Inspector regarded all structures as a complex, interconnected system. Therefore, he argued in his reports that certain embankments should only be built if other arks were also being built at the same time, for example, on the other side of the river and/or downstream. These complex hydraulic engineering interrelationships were described in the inspector’s reports. From a hydraulic engineering point of view, it made no difference to him whether an ark was—from an administrative perspective—sovereign or particular. His observation of specific hydraulic problems on the river and his proposed solutions could not conform to this strict separation and had to go beyond it (Figure 4a).

Due to the traditional social organization of hydraulic engineering, separate reports were submitted to different authorities. The central government in Vienna received a report on the inspection of sovereign arks at the end of the year or at the beginning of the next year. At the same time, the Privy Council in Innsbruck received a separate report on the inspection of particular arks. However, unlike the unlike the inspector’s observation, the competent authorities’ and the local communities’ observations of river-related problems did not cover the entire river basin and all arks. They remained largely limited to those arks for which the respective authorities and communities were responsible (Figure 4b).

This led to serious problems because sovereign embankments were often located directly next to particular ones and were thus closely connected in terms of hydraulic engineering (Figure 5). On the map made by Main Ark Inspector Samuel Gottlieb Besser in the year 1778, particular arks are identifiable by the red and black dashed lines, while sovereign arks are depicted by continuous red lines. The map was created to clarify unclear responsibilities for hydraulic infrastructure on the River Inn.

The court chamber in Vienna had to determine the right improvements and new construction to make for the sovereign arks. The central authority usually followed the inspector’s instructions; the only criticism was that the costs were too high. Various Ark Building Masters ultimately carried out the repairs and constructed new embankments from the beginning of February. They had to organize the transport of materials (stone, timber, sticks) to the river in advance and hire workers to carry out the work. During the winter, the large quantities of stone required were transported to the construction sites on sledges from quarries in the surroundings. Timber (mainly spruce and alder) was obtained from the floodplains or from forests in the vicinity.

The Inspector declared the 2nd of February, the Feast of Candlemas, as the start of construction work because at this time, the winter water level was at its lowest [48,49]. The time span for work on and in the river was only limited to about two months and depended on the seasonal fluctuation of water discharge. From mid-April onwards, snow began to melt in the mountains, meaning that the water level in the river increased significantly. As a consequence, effective interventions in the river became more difficult. In spring—around mid-April—the Inspector began his second round of visits to check whether the commissioned work had been completed at low water. Since the financing of the sovereign arks was covered by the Court Chamber and special Ark Building Masters were employed, the complex organization and construction of sovereign arks usually worked well.

The inspector’s perception of the problems on the river was quite different from that of the various local communities and the authorities involved. The former planned an integral river management intervention to straighten the Alpine stream, while the latter focused only on those embankments they needed to maintain. At first glance, hydraulic engineering was institutionalized in the mid-18th century with the establishment of the Main Ark Inspection authority by the authorities in Tyrol. However, despite this institutionalization, the social organization of hydraulic engineering remained unchanged in its old structures, with different rights and duties pertaining to the different actors on the river. This, in turn, had a massive impact on the competencies of the central hydraulic engineering actors, that is, the Main Ark Inspectors and, from a practical point of view, on the straightening of the Inn. The study of hydraulic engineering in environmental history should by no means be limited to purely constructional and technical aspects—although these are of course worthwhile to study—but should also focus on the complex structures of the social organization of hydraulic engineering [50,51,52,53]. This is even more important because it was not always clear and transparent to contemporaries, while being consistently problematic for them.

4. Municipalities, Communities, and “Throwing Arks”

In contrast to sovereign arks, there were frequent problems with particular arks. In many cases, those responsible for maintaining the arks had no interest in following the inspector’s new guidelines for straightening the river. Traditionally, these communities built arks perpendicular to the river banks. With these “throwing arks”, the river was “thrown” to the other bank in order to protect the riparian zone that they used extensively. Martin Stuber analyzes so-called topographic descriptions from Switzerland to describe “the logic of the local exploitation system […], which keeps many rural people from draining their boggy meadows” [54] (p. 174). In Tyrol, the riparians were even able to gain new meadows through the construction of throwing arks. At the same time, this type of construction was harmful to both navigation and downstream neighbors. The question of who had specific responsibility for hydraulic engineering was a matter of negotiation. Thus, this issue was controversial and caused considerable conflict.

The Main Ark Inspector therefore had the challenging task of convincing local people of the benefits of straightening the Inn. These attempts at convincing people to “follow the straight line of direction properly and as much as possible” cost Rangger “much effort and work” [55]. This is a kind way of putting it, considering Rangger’s many complaints about these communities’ motivation to undertake construction work on the river. The map described in this report has been preserved. The accompanying map clearly illustrates that the actual construction of the arks in the municipality of Ambras (No. 32)—next to Innsbruck on the right bank—deviated greatly from the red river direction line and were built perpendicularly to the river bank, like throwing arks (Figure 6). The non-negligible economic importance of the floodplains for local communities in the early modern period can be seen as a factor in the resistance to the straightening. In this sense, the conflicts over the straightening of the Inn can also be interpreted as a defense of the commons against state claims [56,57].

In their deliberations with the local people, the Main Ark Inspectors argued principally on the grounds of hydraulic engineering principles and knowledge. On the one hand, the construction method they proposed was much stronger and more sustainable, saving material and work in the long run. On the other hand, the straightening of the Inn allowed farmers to reclaim extensive alluvial areas along the river, thus gaining agricultural land. Despite attempts at persuasion, various petitions from the local people and reports from the inspectors indicate that the communities saw the promised benefits as being not so much for themselves, but primarily for navigation, and thus solely for central government. Additionally, from their point of view, central government should provide the funding for these works. To some extent, the view of the Main Ark Inspectors coincided with that of the local communities. They complained about the high financial burden and the fact that small communities had to build embankments along large stretches. During the next inspection in spring, the communities proffered various reasons for not building the arks. They argued that their own agricultural work was more important than the proposed construction work. Other reasons given were that they lacked the stone to complete the embankments or the water level of the Inn had risen too early.

To illustrate these conflicts in detail, a map drawn in autumn 1753 by the Main Ark Inspector Franz Anton Rangger is highly instructive (Figure 7). This large format (222 × 55 cm) colored pen drawing depicts a section of the River Inn, approximately seven kilometers long, facing slightly northeast, at a scale of about 1:2.300. The Inn is portrayed at the three villages of Kolsass (bottom left), Terfens (top left), and Weer (bottom center), which are not shown on the map. On the left bank, 16–19 people from the municipality of Terfens were responsible for the embankments. On the right bank, the municipality of Kolsass was responsible up to the entry of the Weerbach torrent (No. 8), and from this tributary onwards, the responsible party was the municipality of Weer.

In the legend at the top right, Rangger describes this section of the Inn as a “very poorly managed area”, which he had already mapped in 1739 and which had “already been inspected several times by high commissions”. However, even though this stretch of the river had attracted the attention of the provincial government in Innsbruck for some time, a systematic plan for hydraulic engineering had never been drawn up. Rangger’s proposed plan for straightening the river, as indicated by the red direction line on the map, aimed to address this unsatisfactory situation. The new map was considered to provide a suitable foundation for planning the straightening of the river bends in this section.

Due to its meandering course, the Inn was particularly wide and extensive in this area. Sandbanks, side arms, and tributaries are evidence of the strong dynamics of the Alpine river system. Extensive wooded floodplains lined both banks. Human intervention in the riverscape is documented on the map in the form of arks and is labeled with numbers. These refer to a detailed written explanation of what is depicted by the Main Ark Inspector, in order to show what is required to straighten the river. Although the map was separated from the written source in the archive during the 19th century, the rudimentary information provided still enables an understanding of the map. However, the central aspects of the configuration of the Inn’s riverscape in the mid-18th century can only be understood through other written sources. This is the only way to reconstruct the interaction between anthropogenic interventions and the actual shaping of the river. The letters and numbers marked at arks or at certain points on the map refer to an external document containing further information on these embankments and the nature of the river which was able to be relocated through extensive research. The Tyrolean Regional Archives contain a total of eleven fascicles, including concept papers, correspondence, orders, and plans of the Main Ark Inspection authority related to hydraulic engineering. These collections are extensive but poorly cataloged. They cover the entire period of the hydraulic engineering authority’s existence from 1745 to 1792. On closer examination, a report in fascicle three has been found to refer to this map [60].

As early as August 1753, Rangger stated that “future tranquility for both neighboring subjects and navigation could never be achieved” in this area unless the Inn was straightened on both banks simultaneously and purposefully [61]. Regardless of his numerous proposals since 1747, this had never happened, because the three municipalities of Kolsass, Weer, and Terfens, which would have had to pay for and also build these embankments, were unable to provide the necessary human, material, and technical resources. At the same time, Rangger warned of an increasing risk of flooding and obstruction of navigation. On 4 September 1753, the Representation and Chamber commissioned the Main Ark Inspector to draw up a map of this section of the river. In a 30-page report dated 21 October 1753, the hydraulic engineering expert finally detailed his plan to straighten the Inn. This report describes the meaning of the 53 figures on the map, as well as the construction profiles and different types of necessary arks.

According to the assessment of the inspector, the meandering of the river in this section was not due to the natural dynamics of the river, but due to human intervention and the construction of throwing arks. The throwing ark (No. 4) “filled in and removed the old course of the river using gravel and sand” [60]. This allowed for the creation of the two pronounced bends of the Inn. Rangger only represented this embankment with a dotted line on the map because it was removed from the Inn in 1750, after its harmful effects had already been pointed out several years beforehand. The throwing ark is situated on the left bank on the left side of the map (Figure 8). The intertwined relationship between fluvial dynamics and human action on the river is impressively emphasized by the effects of this throwing ark. The throwing ark propelled the river to the opposite bank. As there were no embankments on the right bank, the Inn flowed unhinderedly towards the confluence with the mountain torrent. Navigation in this area became more challenging due to the sharp left-hand bend of the river. For this reason, in the spring of 1752, an interim ark (No. 6) was constructed at a cost of 400 guilders, funded by the Hall salt office, just before the confluence of the River Inn and the Weerbach torrent.

In the following decades, the proposed broaching of the two river bends, suggested by the Main Ark Inspector from 1747 onwards, failed not so much due to problems, but rather due to the refusal of the particulars to provide the necessary financial, material, and human resources for this difficult and costly hydraulic engineering project. Although the inhabitants of Terfens were responsible for creating the two bends by building the throwing ark (No. 4), the municipality of Kolsass on the other bank would have had to cut through the first bend of the Inn (Nos. 17–18) over a length of 123 m. It was only to be expected that the villagers would repeatedly refuse to carry out the construction. In the area of the so-called White Wall (Nos. 45–47)—below the compass rose on the right-hand side of the map of 1753 (Figure 7) and appearing on the map of 1778 as “die Weisse Wand” (Figure 9)—the course of the Inn changed significantly in the following years. In the summer of 1756, a ship even capsized there because the thread of the current was directed towards this high, natural cliff [62] (Figure 9).

The Main Ark Inspector’s on-site visits, his reports, and this map provided the government with an accurate depiction of the current situation on the river. However, the integral river management designed by the Main Ark Inspector to straighten the Inn did not achieve the desired result and efforts remained fragmented, especially in the area of particular arks. This was due to the division of responsibilities between the sovereign and their subjects. The social organization of hydraulic engineering significantly hindered the straightening of the Inn in Tyrol. The local people who were put under obligation to build the arks had no interest in straightening the river and consequently declined to build the prescribed arks; this was in part due to the excessive costs and time required for construction. Additionally, they often lacked the technical expertise to construct the material-intensive embankments, even with the assistance of the Main Ark Inspectors. Instead, for river management they frequently relied on traditional throwing arks.

5. The Wet Border between Tyrol and Bavaria

Since the 16th century, the Inn has formed a wet border between Tyrol and Bavaria just below Kufstein, which still exists. In pre-modern times, the wild riverscapes had very limited use as a fixed “natural border” due to their dynamic nature. Therefore, the conflicts between the two territories along the wet border on the river are as old as the border itself. They can be traced to the 16th century in archives in Innsbruck, Munich, and Vienna. The wet border between Tyrol and Bavaria was marked by disputes similar to those between the neighboring municipalities within Tyrol. At the state border, however, the hydraulic engineering conflicts were also territorial in nature and therefore politically complex, gridlocked, relentless, and intractable.

A large colored map by Franz Anton Rangger, dated 16 June 1746 and mounted on canvas, documents these conflicts (Figure 10a). The map measures 213 × 44 cm and the scale is about 1:5000. For practical reasons, it faces west rather than north. The map shows the shared border along the river between Tyrol and Bavaria. While the upper half of the map shows the Bavarian territory of Auerburg, the lower part of the map shows the Tyrolean territory of Kufstein. It was drawn in the course of negotiations between Tyrol and Bavaria to settle the border disputes on the Inn by treaty. In 1746, however, no mutually satisfactory solution could be found. The Bavarian Main State Archives hold a copy of the Bavarian version of this map from 1787 (Figure 10b). It was not until 1760 that a treaty was reached between Tyrol and Bavaria regarding river management construction on the common border of the Inn. Thanks to this contract, two more identical maps of this section of the river from 1760 exist and were obtained by this study (Figure 10c,d).

The legend at the bottom left of the map provides important information about the river’s frequently changing course and the role of human intervention. For example, reference is made to a completely different course of the river from an earlier period. However, this flow of the river was unfavorable for the local communities on both sides. The municipality of Ebbs—for whose representation the map had to be extended at the bottom—lost about 53 hectares as a result of the new course of the Inn. In addition, the risk of flooding for the village increased dramatically due to the river’s changed course. The map also contains suggestions about the project to straighten the river. This can be clearly seen by the direction line drawn in yellow. This line indicates what is assumed to be the ideal course of the river, which corresponds quite precisely with the course of the Inn today.

However, even this map can only be properly interpreted with the help of other written sources. The first fascicle with files from the early days of the authority and Rangger’s activities from 1745 to 1748 contains an extensive, undated report, which on closer inspection turns out to be the description of the map recorded in June 1746 [67]. The 23-page report is divided into two main parts: after a brief introduction, Rangger explains the meaning of the 21 numbers marked on the map. These describe the current state of various structures, but also refer to arks built in the past and their impact on the river. The second part provides an explanation of the letters (A–Y) on the map, which refer to the planned embankments on both the Tyrolean and Bavarian banks, the materials required for their construction, and their costs. They thus depict a new, future river course, which is already anticipated by the “direction line”. Like the previous map of 1753, this map indicates not only the course of the river at the time the map was drawn in June 1746, but also an older course of the river and its future appearance as predicted by Main Ark Inspector Rangger. The map thus contains two additional layers of time, which can only be read through the explanatory report. This allows for a diachronic dynamization of the static map.

According to the report, the constitution of the Inn on the map, but especially the four bends of the river on the left, were mainly determined by human activity on the river. The meandering of the Inn was not due to the river’s natural dynamics, but due to human intervention and the construction of throwing arks. Rangger’s comment on the origins of the river’s meandering course is instructive. The Inn meandered along the wet border—as described in the previous section—mainly due to the construction of throwing arks. To illustrate this, the Main Ark Inspector pointed out a systemic hydraulic engineering context that spans several kilometers of river and covers the past 68 years: “the throwing ark No. 2 built by Bavarians” caused damage of several thousand guilders at Oberndorf and Ebbs [67]. This embankment had also damaged “Bavaria itself and was the first cause of the serpentine course of the river.” Four of these river bends are visible on the left-hand side of the map: two in Tyrolean territory below the yellow direction line, and two above it in Bavarian territory. The first bend on the Tyrolean side is marked by the northward river bend, which is, according to Rangger, significantly intensified by a Bavarian throwing ark (No. 2). A second bend is therefore located on the Bavarian side (No. 5). The third bend—again on the Tyrolean banks—is the arm of the river at Ebbs (Nos. 10–11), which the map shows as almost dry. The fourth and final bend on the Bavarian bank has its turning point at Antenstein (No. 14), at the foot of the so-called Floriani Mountain, a small ridge that runs from west to east towards the Inn and is clearly visible as such on the map due to the shading (Figure 11).

The Bavarian throwing ark (No. 2) directed the Inn towards the Tyrolean Oberndorf. To protect themselves and their fields from the threat of flooding, the Oberndorf villagers had to build equally strong embankments at a cost of several thousand guilders, according to Rangger’s quote. The report does not give an exact date for the construction, but Rangger goes back as far as 1670. The throwing ark located on the Tyrolean bank, just below Oberndorf (No. 9) intensified the formation of another river bend by directing or throwing the water back to the Bavarian side. Rangger stated that the hydraulic engineering problems caused on the Bavarian side could not be attributed to the Tyroleans’ throwing ark. However, their own throwing ark (No. 2) may have caused damage “to the Bavarians themselves”. The Tyrolean throwing ark (No. 9) was demolished in 1718 as part of a treaty settlement. However, the structure’s presence in the Inn forced the people of Auerburg to defend themselves against it; this is evident in the long arks (No. 5) and the transverse structures (No. 6) located in front of the so-called Guggenauer ditches. The River Inn once completely passed by the Guggenauer ditches, but these transverse structures (No. 6) diverted its flow towards the Tyrolean banks. In 1718, these blocked ditches (No. 6–7) on the Bavarian bank should have been removed, as should the Tyrolean ditches (No. 9). As only the latter were removed, the Inn diverted towards Ebbs from 1718, forming the third bend. The fourth and last bend is therefore less due to human intervention, as the Inn had already flowed towards Antenstein previously and the direction of the flow at the end of the Ebbser bend was not directed towards Antenstein by arks.

However, it is instructive to see how the successful straightening of the Inn bend (Nos. 10–11) at Ebbs was achieved. This example demonstrates that the pre-modern technical interventions for straightening rivers were by no means inadequate. Actualization depended primarily on the presence of the appropriate political, financial, and organizational conditions. When Tyrol and Bavaria faced each other as warring parties in the War of the Austrian Succession (1740–1748), the conditions were deemed appropriate and fitting. In 1742, Auerburg was occupied by Tyroleans, who took advantage of the political situation to straighten the river at Ebbs [68]. “On military orders”, they demolished a 115-meter-long ark (No. 8—dotted line) on the Bavarian riverbank, which was described as “illegal” [67]. They used the material to build a massive ark on their own bank. This embankment (No. 13) forced the Inn away from Ebbs “for the sake of future tranquility” and back into the “old riverbed” [67]. The village not only regained a large floodplain in territorial terms but was also protected from future flooding. From the Tyrolean perspective, the treaty of 1718—which the Bavarians had violated with their arks (Nos. 6–8)—was restored.

A brief glance at the sources of the Bavarian Main State Archives reveals a similar pattern regarding the anthropogenic origins of the river bends. Nevertheless, there is a significant contrast when it comes to accountability and causation. It was not Bavarian throwing arks that were said to have caused the “ark differences”, as Rangger claimed. Instead, they were considered to be the result of hydraulic engineering and violations of contractual regulations by Tyroleans, especially in 1742 (Figure 12a,b).

6. Torrents, Sediment, and Floods

The administrative structures and the social conflicts along the river already described were not the only reasons for the Main Ark Inspection authority’s failure to straighten the Inn. According to the extensive source material, there is another key reason: the main river received additional sediment from torrents in the side valleys. This is because various materials (stones, sediments, etc.) carried into the main river narrowed the width of the Inn at the confluence with mountain tributaries. As a result, the river’s reduced speed prevented it from carrying these incredibly large quantities any further, causing a gradual rise in the level of the riverbed. Thus, some of the agricultural land in the Inn valley was at times lower than the river itself. This inevitably led to an increased risk of flooding, as the water could no longer drain away from the lower-lying fields. The agricultural areas of the Inn valley—as well as the Etsch valley in Southern Tyrol—were increasingly threatened with transformation into marshland. The phenomenon of rising riverbeds was also recorded on other, predominantly Alpine rivers in the 18th century such as the Rhône [71], the Linth [72], and the Salzach [73], but also on the Alpine Rhine [74,75] and Upper Rhine [22].

In Tyrol, contemporaries attributed the causes of the supposedly natural dynamic of rising riverbeds in the Inn and Etsch to unregulated massive deforestation of the neighboring steep mountain slopes of the valleys. The mining industry in Hall and Schwaz continuously required large quantities of firewood and timber [76]. During the second half of the 18th century, this valuable resource was even transported from the Lech valley over the Fernpass to Imst and then down the River Inn to Hall. Because a considerable distance and altitude had to be covered by road, this transport option was a much more time-consuming and expensive option compared to waterborne passage on torrents and rivers. The effort put into meeting the demand for wood highlights the reality and severity of the timber shortage, which was a serious problem.

In an essay published in 1999, climate and environmental historians Christian Pfister and Daniel Brändli referred to these connections as the “deforestation paradigm”. They assumed that this interpretation “for the first time” emerged in the Pyrenees at the end of the 18th century [77] (p. 303). However, Stefan Lindl was able to prove in 2014 that this interpretation was popular in Tyrol from the late 1770s by analyzing contemporaneous printed treaties on hydraulic engineering [78]. In contrast to Pfister and Brändli, the focus of his work was less on the causal factors of deforestation and more on the bedload itself, which had become increasingly problematic for hydraulic engineering. He therefore stressed the term “bedload discourse” [78] (p. 95). As Lindl neglected to connect his research to the debate on the “deforestation paradigm”, Pfister’s and Brändli’s statement remains the current state of research [79]. Based on extensive archival material from the Tyrolean Regional Archives on the hydraulic engineering authority, it is now possible to reveal that the Main Ark Inspector had already been familiar with these links in the mid-1740s and had analyzed their complexity. The following argument is based on a comprehensive examination of archival material. It suggests that, at least in Tyrol, deforestation may have played a more significant role for these hydro- and geomorphological processes of rising riverbeds and flooding than previously assumed in academic research.

A map from 1748 illustrates the seriousness of the issue of bedload input and its detrimental effect on the straightening of the Inn (Figure 13). The course of the Inn is shown with arrows from left to right and the confluence of a tributary can be seen in the upper left part of the map. The bridge (No. 25) and Landeck Castle (No. 26) can be seen on the right. On the left bank, arks to protect the road are outlined in red and yellow. During a storm in the summer of 1747, a complete backwater of the Inn, which was 20–25 m wide at this point, occurred at the confluence of the River Inn and the Thialbach tributary. The Thialbach dumped so much material into the Inn that it completely clogged up. As a result, people in “Landeck and the villages below were able to walk through [the Inn, RFN] with dry feet, i.e., people scooped the dead fish out of the water by the bucketful” [80]. In addition to this rather pleasant consequence of the event for the local population, there were also less pleasant side effects. Most of the arks on the left bank (No. 9, Nos. 17–19) and the road (No. 27) were destroyed, forcing commercial traffic heading to Switzerland to use the much more difficult and steeper road above (No. 28). In the years that followed, the Inn was repeatedly dammed up in this area due to the massive influx of material from the torrent. The hydraulic engineer considered deforestation along the Thialbach as a cause. According to Rangger, the angle of the confluence was crucial, as it was 90 degrees. The sediment was pushed perpendicularly into the river and therefore blocked the flow.

Rangger also emphasized in other reports that this was a man-made problem related to deforestation [81]. In doing so, the engineer offered a coherent interpretation of the events and a complex understanding of the bedload problem. The increased input made flooding more likely and thus also had a serious impact on the straightening of the Inn because, “the riverbed […] is raised with useless gravel, which is why the fertile estates /: which are usually lower than the river:/ are overflowed and made barren by the overflowing water” [82].

The bursting of the Thialbach and the resulting backwater of the Inn was not an isolated event. The summer of 1748 was marked by devastating mudslides and floods throughout Tyrol [83]. The village of Grigno, situated in the southern part of Tyrol, was largely destroyed by a mudslide from the torrent of the same name. A map by Rangger, which depicts the planned protective structures, illustrates the extent of the destruction [84]. The Privy Council in Innsbruck therefore issued a circular on 26 August 1748 addressed to all the authorities in the province and to Rangger in order to find out “where these so severe and violent water discharges, mudslides and floods had originated” [85]. Based on the feedback, preventative measures against natural hazards were to be developed and implemented. The decree issued eight months later can be interpreted as the political implementation of the measures demanded by Rangger in various reports. The political decision makers were therefore already aware of the full extent of the bedload problem and its causes at this time. In the decree of 12 April 1749, the horizon of interpretation of the devastating events of the summer of 1748 is clearly focused on the deforestation paradigm or the bedload problem and the lack of, or inadequate, protective measures [86]. Reforestation of deforested mountain slopes was ordered, and a ban on deforestation on still-forested slopes was imposed. Additionally, restrictions were placed on timber drift on torrents and rivers. These measures were intended to reduce erosion both on the mountain slopes and on the river banks, thus preventing the huge load of sediment from entering torrents and rivers.

In the years that followed, however, mudslides became more frequent and caused extensive damage. This was due to the inability to solve the problem in the short term as reforestation would take decades. Furthermore, the required measures were frequently not implemented in practice. After devastating floods occurred throughout Tyrol at the end of August 1757 [87], the engineer Jean-Baptiste Brequin (1712–1785) from Lorraine was sent to Tyrol by imperial order [88].

The southern part of Tyrol with the Eisack, Talfer, and Etsch Rivers was particularly affected. On the latter river, the water between Merano and Rovereto remained stagnant for several days due to flooding, forming a lake that was unable to drain away. Brequin was commissioned to investigate the causes of these extreme events and to develop precautions for future flood protection. In a 40-page report written in French about the causes of the flooding, the engineer analyzed the complex interrelationships between deforestation and sediment transport [89]. These interrelationships had already been identified ten years earlier by the Tyrolean Main Ark Inspector. Brequin’s arguments are consistent and convincing. His diagnosis is both remarkably far-sighted and complex, given that he was not familiar with the hydrological conditions in Tyrol as an external observer. However, the explanations of the engineer, who was sent from Vienna, did not go beyond the interpretative horizon of the Main Ark Inspector. He could certainly draw on the experience of his local companions, although Rangger was not one of them. The resulting interpretation, despite his lack of previous contact with Rangger, is not solely due to the engineer’s abilities. These interpretations were already widespread in Tyrol at the time.

The ex-Jesuit and natural scientist Franz von Zallinger took up the current state of knowledge in the bedload discourse and presented it in his theoretically well-founded “Treatise on Floods in Tyrol” published in 1779 [10,11,78,90]. For example, unlike the practitioners of hydraulic engineering, he advocated bedload retention barriers in the valleys in order to minimize the amount of bedload entering the main rivers. It is precisely such pioneering demands that explain Zallinger’s importance in the hydraulic engineering discourse of the 19th and 20th centuries [78]. In the pre-modern era, hydraulic engineering on Alpine rivers was carried out in very different circumstances from that on rivers in the plains, such as the Danube or the Rhine. The technical means of the time were unable to cope with the steep gradients and incredible dynamics of Alpine torrents [91]. The problem of riverbed elevation due to increased bedload input could not be solved in the course of the 18th century. Although the straightening of the river was regarded as a solution to the problem by the Main Ark Inspection authority, the bedload itself was a major hindrance to the straightening of the Inn.

7. Conclusions or: The Long-Term Transformation of the River Inn

On an abstract level, the failure to straighten the River Inn can also be conceptualized as a tension between “hard” and “fast” infrastructures on the one hand and “soft” and “slow” infrastructures on the other. Tim Soens explains this concept using the example of coastal and river management in a long-term perspective [92]. “Hard” and “fast” infrastructures emerged in the 19th century and have continued into the 20th and 21st centuries. They are based on expert knowledge and strict top-down implementation. In the pre-modern era, “soft” and “slow” infrastructures were widespread. According to Soens, indicators of such an infrastructure include the participation of multiple stakeholders in decision-making processes, which can sometimes be lengthy, and a corresponding bottom-up implementation of measures. In addition, massive embankments on rivers as elements of hard infrastructure were “often only a minor part of flood protection mechanisms, which relied primarily on extensive wetlands able to compensate river flow rates.” [92] (p. 189). This general finding also applies to Alpine rivers, but to a minor extent. The larger volumes of sediment and the steep gradient required more massive embankments than those on rivers in the plains.

The Main Ark Inspection authority was intended to establish a “new socio-technical regime” in Tyrol by inventing an “infrastructural acceleration” [92] (p. 197). The intended construction of many new arks to straighten the River Inn can be regarded as hard infrastructure. This included the “decreasing participation of local stakeholders in the decision-making process”, to quote Soens [92] (p. 197). However, in Tyrol, almost 50% of all arks were left to local communities and municipalities, who preferred to build throwing arks. The state was unwilling to provide full funding for its proposed structures. Furthermore, it was at this point that the establishment of the “new socio-technical regime”, and thus a strict top-down implementation of the straightening of the River Inn, failed in the 18th century. The twice-yearly visits initiated a shift from a reactive to a preventive hydraulic engineering approach. However, as maintenance and financing remained with the communities, no “new socio-technical regime” was able to develop along the Inn. Hydraulic engineering on the Inn remained largely rooted in old structures and therefore “soft” and “slow”, as Tim Soens observed for pre-modern rivers in general [92].

To connect these very environmental–historical results to the wider context of integrated river management, two key points should be emphasized. On the one hand, a long-term perspective on the transformation of the Inn in Tyrol reveals that the present-day formation of the river has been shaped by three infrastructural projects over the last three centuries. In the second half of the 18th century, initial efforts to straighten the Inn were focused on navigation and land reclamation. During the 19th century, hydraulic engineering and the transformation of the riverscape in the Inn valley continued to be driven by land reclamation. However, the main changes were the result of the construction of the railway in the middle of the 19th century. In the 20th century, the riverscape was finally shaped by the construction of the motorway through the Inn valley. Established in the 18th century, the principles of straightening the river and of “conquering” nature to the maximum extent remained influential. It was assumed that the “major river corrections had led to a long-lasting solution to the river engineering problems in the affected stretches” [93] (p. 746). However, for the last 30 years or so, precisely those areas that have been reclaimed from the rivers over the last three centuries have been the focus of current hydraulic engineering measures. In the wake of climate change and biodiversity loss, the loss of the once extensive riverine landscapes weighs all the more heavily today. From an ecological perspective, the consequences of the straightening of the Inn are regrettable, as largely pristine (or near-natural) rivers are hotspots of biodiversity. The river restoration carried out in 2022/23 in the Upper Inn Valley between Stams and Rietz demonstrates that in the 21st century, rivers are still undergoing significant changes, which are often in the opposite direction to the historically long-lasting hydraulic engineering concepts of straightening and utilization of rivers for human purposes. The current measures undertaken to restore rivers are important and demonstrate that the quoted statement about the “long-lasting solution to the river engineering problems” [93] was by no means definitive. However, the potential for restoration of the Inn is very limited due to the intractable conditions and the material design of the “hard” infrastructure of the past three centuries.

On the other hand, it is evident that the results of environmental history research are crucial for the establishment of reference conditions within the framework of river restoration. Only a minor percentage of rivers afford the opportunity to reconstruct such natural conditions from the current state of the river [94], which highlights the great importance of historical maps. As the historical maps can only be contextualized through other written sources and can therefore only be interpreted in the first place, the integration of environmental history research into restoration processes is indispensable. As GIS-based research in this field has been fruitful [39,41,95], future projects on the River Inn could benefit from a combination of the analysis of historical river maps with GIS-based research.