River morphologies, large and small

7Environmental historians aim to tell the stories of riverine landscapes as combined natural and human histories.11 They investigate ways of living with or attempts to conquer natural dynamics, study human interventions into ecosystems and the resulting long term changes, in particular unwanted consequences of interventions and human reactions to them. Their work focuses on natural changes in the context of changes in human society and vice versa. They need to take nature’s role in history seriously12 and consider whole river systems rather than just a section of one river. Rivers, Castonguay and Evenden write, “unite a spatially extensive network of hydrological flows, reaching back to a height of land forming the outer limits of a basin, but are also characterized by a hierarchy of streams and tributaries. […] It matters where a city is located along a river, of what size, undergoing what dynamic seasonal and historical changes.”13 But to date, only few studies are based on a comprehensive understanding of the distinct characteristics of urban waters and the resulting unique socio-natural sites.

8Natural sciences conceive of rivers as systems of connected river channels in a drainage basin or catchment area, the area that contributes water and sediment to the river. Catchments are separated by topography. They are composed of channel segments with distinctive geometric properties and size that differ in length, slope, drainage area and bifurcations and follow morphometric laws. A hypothetical ideal river system consists of a mountain belt that delimits steep valleys and narrow floodplains, where river channels cut into bed-rock and coarse-grained alluvium and an alluvial fan, where the main channel enters the plain and branches into several arms that convene further downstream. The following section exhibits a broad valley and floodplain where tributaries discharge into the main channel, and finally a delta where this channel, often fanning out, flows into a lake or the sea.14 Hydrologists use the concept of “stream order” to summarize basic characteristics of different sized stream segments. The Wien River catchment is shown in Figure 1 as an example.

9River systems are fed by precipitation in the catchment area. Some of it returns to the atmosphere by evaporation and evapo-transpiration, but the rest reaches the river under the influence of gravity over the surface as runoff or through the ground as groundwater. Water supply varies over space and time depending on climate, seasonal weather variability, snowmelt and cosmic constellations (via tides). Varying flow conditions over a period of time make up a river’s distinct “flow regime” that depends on latitude, geological properties of the underground and morphology. Vegetation, land use and the geometry of the drainage system also contribute to the flood regime.15 The rapidity of the flood wave and thus peak discharge volume resulting from heavy rainfall depend on ground permeability and water saturation. Vegetation, soil, subsoil and ground water act as regulators that attenuate climate and weather variations and delay effects on the discharge. Human interventions in the catchment’s soil cover therefore strongly affect the flow regime.

10Sediment amount and composition depend as well on geology, on the geometry in the catchment area (e.g. slope) and on climate. Sediment supply to rivers varies in conjunction with water supply and a wide range of human practices connected to agriculture and forestry, construction and mining. Sediment eroded in the headwaters may accumulate in floodplains,16 but gravel and sand transported downstream into a city were welcome building material. Transported nutrients and sediments can also become fertile soil downstream. Also, rivers connect ecosystems along their course, allowing for the movement of fauna and flora.17

11Temporal and spatial variability are fundamental for river systems. Drainage and channel patterns are dynamic and change over time; human interventions into rivers and catchments are one factor contributing to these changes. The “basic elements” of hydropower—the volume of flow and the amount of fall—are a product of many and varied meteorological, geological, physiographic and hydrologic conditions.18 The relative location also matters. While slope and sediment erosion usually diminish, the volume of flow and sediment deposition increase from spring to mouth and from rivulet to main stream. These parameters alone result in situations widely different between locations (fig. 1 and tabl. 1).

Fig. 1. The catchment of the Wien River around 1825

12At all times people wanting to use rivers and floodplains had to “understand [them] in order to deal with problems such as floods, water supply, design and construction of artificial channels, river-bank erosion, sedimentation in reservoirs and navigated waterways, restoration of freshwater habitats, and remediation of polluted surface water and groundwater”.19 To understand riverine processes, long-term records and knowledge of antecedent conditions are indispensable.20 River system characteristics are hence as fundamental to the environmental history of pre-industrial riverine energy use as the social organisation of city administration, feudal politics, property or water rights.

Energy from Rivers

13Before the spread of fossil fuels and, later, electric energy, people relied on three types of energy to provide movement: human and animal muscle (who in turn need biomass for food and feed to maintain their strength), wind, and flowing water. All were used to overcome distance or exert motive force, and all had limits. Rolf Peter Sieferle pointed out that the amount of food needed to carry freight limits transport distance.21 Wind and water can move greater masses than humans and animals but are subject to “geographical limitation”22—they are not available everywhere and at all times.

14Sailing boats are a very efficient means of transport but mainly operate on larger waters. Because they can haul goods fast and over great distances, seaport-hinterland interactions are very distinctive and decisive for the energy metabolism of a city.23 Major rivers were equally important for the provisioning of cities. Downstream transport, enabled by gravity, is very efficient, but energy was needed, if boats were to be brought back upstream.24 A model of hinterland sizes for various urban centre sizes showed that transportation was the main constraint to urban growth under pre-industrial conditions.25 Access to transport by boat could extend the urban hinterland along the waterborne supply routes and allowed medieval harbour cities to grow much more populous than inland cities.26

15Floating of timber and fuelwood from mountainous forest areas to cities downstream was decisive to provide urbanites with building material and fuel.27 This practice led to thorough alterations of small streams and larger rivers in peripheral regions.28 As one horse can pull about 1 ton of goods on the street, but move a boat of 30 tons on a waterway,29 artificial canals to connect rivers and even oceans such as the Canal du Midi (built 1667-1681) were established.

16Watermills provided another way of using gravitational energy. As water flows downward, its potential energy is converted into kinetic energy that can drive a waterwheel. The motive power of the wheel is then transferred to the machinery, either directly as rotary power or via transmission to provide reciprocating movement. Although this power could neither be stored nor transmitted over a large distance, innumerable adaptations of machinery made it useful for a wide range of production processes, from the grinding of grain to crushing, sawing, hammering, sharpening, boring, pumping and pulling of diverse materials.30 Mills were indispensable for the urban metabolism, e.g. for flour, oil and barley for beer.31 US engineers in charge of censuses on potential hydropower use aptly described most suitable topographies and flow regimes for milling in the 19th century.32 Riverine characteristics were, as becomes clear from this source, of importance also for the mill as a stationary technological system.

17Flowing water also helps to dispose of sewage, wastewater and solid waste. As modern energy statistics focus on technical energy, they exclude the energy embodied in biomass. Rivers are habitat for fish and other riverine animals, including migratory fish species that travel long distances, delivering nutrition to urbanites.33 Landscapes and habitats depend on the fluvial dynamics of rivers. Frequent and extraordinary floods facilitate pioneer ecosystems which are among the most productive. Floodplain forests with their fast-growing pioneer trees have been used as sources for wood. Meadows were used for grazing and as hunting grounds. Vegetables and fruit were cultivated on the nutrient-rich floodplains.

18Using parts of river systems consisting of several channels offered more possibilities to make use of these various riverine resources, enabled to avoid conflicts to some extent and increased options. To create certain river types, urbanites built artificial or partly artificial tributaries or distributaries such as canals or mill creeks that supported more uses than their names suggest. In the following section we build on two projects that allowed to analyse the mutual history of Vienna and its waters in detail.34 We try to cover the whole variety of waters in the river system and the distribution of energetic water uses in the early modern city to show how distinct socio-natural sites complemented each other to satisfy urban demands.

Transport

24The Danube was the only navigable river in Vienna and shipping was the river’s most important function.40 Apart from raft- and ship-based transport, Vienna’s supply relied on highly inefficient transport by cart. The Danube and its large mountainous tributaries connected the city to Bavaria, Upper and Lower Austria for the provision of food, fuel and construction wood and other commercial goods. Ships arrived to the city on the Wiener Arm/Donaukanal. Stabilizing the river arm against the Danube’s dynamic to relocate further north and providing a minimum flow for shipping had been a main goal of regulation projects from the beginning of the 16th century.41 Food and other goods were sold directly on the riverbanks or brought to nearby markets. Around 1835, annually about 250.000 metric tons of goods were transported to Vienna via the Danube.42 As navigation was so important on the Donaukanal, all other potentially interfering river uses were either forbidden or had to subordinate (cp. Fig. 3).

Fig. 2. Vienna’s waterscape. Geomorphological zones and aquatic networks around 1780.

25In 1794 a group of landowners proposed to connect Vienna to its south-eastern hinterland by a shipping canal. Once built, Wiener Neustädter Shipping Canal, a roughly 65 km long artificial waterbody, played an important role for provisioning of the city until it was replaced by several railway lines between 1848 and 1879.43 The canal consisted of 46 basins with almost horizontal ground separated by sluices to overcome the height difference (circa 100 m). With narrow boats operating on the canal, one horse could pull 30 to 50 tons—about 25 to 30 times more than by transport over land.44 The history of planning and maintaining the canal reveals various intermingled state and private investment interests. Chief engineer Sebastian von Maillard used energy saving as an important argument to convince Emperor Franz II. (I.) of the project. Draft horses would be available for military purposes; feed and meadows could be saved for cattle.45 Up to 70 boats operated on the canal between April and September, resulting in a yearly average of 5.500 freights, comprising of 70.000 m³ of wood, 6,5 million bricks, 12.000 tons of coal, 19.000 tons of gravel and other building material and 185 tons of other goods in the 1830s and 40s.46

26Wien River was the only natural tributary used for transport. Wood was floated from the Viennese Woods in the 17th and 18th century. This ended in 1754 after a logging dam had burst during a flood in 1741, causing severe damage.47 Other sources suggest that log driving was practiced until the depletion of the surrounding forest at the end of the 18th century.48

27When the first Austrian Danube Steamship Company was founded in 1829, the Danube was used also as an upstream route from south-eastern cities and regions. Donaukanal was still used to approach the city, but all passing ships utilized the main riverbed. Although several railway lines were established in the following decades, river transport increased in importance. In the late 1860s, about 600.000 tons of various goods reached Vienna via the Danube annually. Between 1835 and 1865, the share of cereals transported by ship and consumed in the city increased from 10 % to over 80 %.49 Rearranging the river as a waterway with a homogenous riverbed suitable for steam ships was one of the major aims of the Danube regulation. Transport was the dominant river function at the expense of others such as mills and fishing—until the construction of power plants after World War II.

Mills

28Suitable locations for using the water’s kinetic energy with mills were astonishingly scarce (see Table 1 for the possibility of operating mills on the different waters). The number of watermills within today’s city limits remained relatively stable at about 80 locations throughout the 17th and 18th century. Stationary mills at the Wien and Liesing River and boat mills on the Danube each contributed about half the mill sites. At the Wien and Liesing, mills were located in river sections with stream order 3 to 5 that provided appropriate conditions with respect to discharge and channel slope. By the end of the 17th century almost all suitable locations were in use. Because of the low channel slope of 0,4 ‰ and the unsteady river arms, no millstreams and stationary mills could be built in the riparian zone of the Danube. The smaller tributaries with stream order 1 or 2 provided higher slopes but very limited discharge and often fell dry in summer. Although they had been used for milling since the late Middle Ages until the Ottoman sieges of the 16th and 17th century, only a few small mill workshops remained until the 19th century.50

29All Viennese millers faced fluctuating flows—destructive floods and paralysing periods of drought—and reduced operability in winter due to freezing. Boat mills found relatively stable working conditions between March and December as they could accommodate varying water levels, could be removed from the river in case of danger or relocated to more suitable anchorage grounds after changes in the riparian landscape.51 But boat millers had to subordinate to transport and land use requirements in the riparian woods.

30Because they impeded shipping, boat mills were forbidden in the Donaukanal.52 Although they obstructed river navigation, their number on the main Danube arm increased significantly in the 19th century. After the ice jam flood of February 1830, a sustained concave riverbank had formed. A combination of favourable flow conditions at this riverbank and easy access for riverine and railway transport encouraged boat mills. Their number almost doubled to 68 locations between the 1790s and the 1870s.53

31Boat mills can only drive basic machinery such as grinding stones. For other, more complex tasks, stationary mills were necessary, but suitable locations were rare. Therefore, slopes at the shipping locks of Wiener Neustädter Shipping Canal piqued the interest of craftsmen and canal administration. Continuous flow conditions and freedom from floods, ice jams and droughts at the canal were used in advertising for the auction of mill sites. Buyers could use the energy to their liking, as long as shipping remained undisturbed.54 Between 1806 and 1930 up to eight businesses operated at the seven locks located within today’s city borders.55

32More than 80 % of all mills in Vienna and the immediate surroundings were dedicated fully or at least partly to grinding grain. Population-growth-driven increase in demand could not be matched despite new milling capacity on new locations on the Danube and Wiener Neustädter Shipping Canal and efficiency gains due to technical innovations—let alone compensate for the sites that were closed down by city administration on the smaller tributaries and the Wien River due to sanitation and flood protection in the densely settled suburbs. Steam was the only solution. The first steam powered mill opened in 1842, but flour import with steamships and trains from Lower Austria and Budapest was even more important, especially for wheat. Almost all rye was brought to Vienna from northern Lower Austria, Slovakia, and Hungary, and processed on the boat mills. In 1869, shortly before the “Great Danube Regulation’, 60 boat mills grinded about 30.000 metric tons of rye, 110 tons per day.56

Fig. 3. Conflicts between different types of energetic river uses on different types of waters

33Mills had to give way solely to transport on navigable rivers, because they were essential for feeding the city (cp. Fig. 3).57 On Wien and Liesing River the subtraction of process water was strictly limited to not interfere with milling.58 Demands of a wider public, such as the dilution of sewage and wastewater, had to cope with the reduced instream flow—until sanitation became a problem that could no longer be ignored.

Fish59

34Fish could contribute significantly to the diet of urbanites. But the Viennese did not eat large quantities, only about 1 kg per year and person, predominantly during lent periods. Among the Viennese rivers, only the Danube provided a significant amount of fish suitable for nourishment. Ottakringer Bach however, was known for the abundance of crayfish.

35The “Great Danube Regulation” in Vienna—but subsequently regulation projects on the whole Austrian Danube—yielded changes in fish population. 57 fish species and two lampreys are considered domestic in the Austrian Danube and the habitat it provides. Only two of them disappeared, but the frequency of occurrence changed markedly. The regulation reduced surface area of water bodies including smaller branches and side arms significantly. Dams and bank stabilisations separated fish from their habitats, especially from areas with lower stream velocity, and prevented migration. Waves caused by passing steam ships were lethal for young fish. Other factors that impacted fish populations were the inadequate protection of young fish in fishing regulations, overexploitation due to unsustainable fishing practices and local pollution by sewage and industrial wastewater disposal. Contemporary fishers observed and discussed all these problems, but the complex ecological interrelations that determined whether a species would prosper or perish were not fully known before the 20th century. Their observations are supported by a quantitative analysis of the amount and kind of species sold on the Viennese fish market. While fresh-water fish from the Austrian Danube and from fishponds dominated the market before 1899, the amount of marine fishes from the Adriatic and North Sea increased significantly thereafter and exceeded freshwater fish by 1900. The decrease of fish in the Austrian Danube coupled with the availability of fast transport possibilities and cooling technology, both a consequence of fossil fuels, explain this development.

Other energetic uses

36Riverine energy was also needed for discharge of sewage, waste water and waste into all streams and rivers, small and large. Only with sufficient flow and slope could wastes be flushed away from their source. The interruption of flow, e.g. through dams, or the abstraction of water for other uses interfered with the disposal function of urban waters and increased sanitary problems and hygienic risks—a situation exacerbated with population growth in the 19th century. Wien River60 and many other small streams suffered from pollution61. Water from the two Alpine Pipelines (Hochquellenwasserleitungen), which tapped springs some 100 km south of Vienna, opened in 1873 and 1901 respectively made additional water available and so allowed to operate a water-borne sewage system that incorporated the small Viennese streams into its network of canals.62 On Wien River’s urban stretch the building authority (Stadtbauamt) closed down seven mills between 1847 and 1856 due to flood risk and sanitary concerns which arose due to the Cholera epidemic of 1855.63

37The importance of resources from the Viennese riparian landscapes—pasture, hunting of deer and birds, timber for fortification and regulation works and fuelwood from trees with short rotation such as willow, alder and hazel—is reflected in severe conflicts between different user groups and manorial lords. It is not usually calculated as energy but was important for the urban metabolism.64