Visualizing urban hydrology
Visualizing urban hydrology: the design of a wet surface
Carolina González Vives
published at MAScontext. Visibility. fall 2012
Within his research about water supply and sewers, the geographer Mathew Gandy includes the publication, in 1865, of the first images of the recently built Paris sewers (1). The photographs contributed powerfully to transform how the city was seen and understood, discovering a new and amazing world beneath its streets, related to technological achievements and the rationalization of urban space. The imaginary map of the city integrates verticality, including underground spaces. Gandy uses Rosalind Williams words to emphasizes “the poignancy of the vertical axis to our understanding of the cultural appropriation of urban technologies, since the subterranean environment is not only a technological construct, but also ‘a mental landscape, a social terrain, and an ideological map“.(2)
Likewise, the recent publication of the photographic report about Los Angeles’ original subway tunnels, reveals another layer of depth of the complex city’s surface, formed by dwellings, front lawns and freeways. The tunnels are added to oil drillings, quarries and excavations, seismic faults and big scale spreading grounds for local aquifer recharge, developing a wider thickness of urban imagination.(3)
Water flow through infrastructures imposes its necessary geometry and connects body and landscape, domestic interiors and public spaces with distant territories, whose run off is collected for the city. Simultaneously urban rainwater and sewage disappear from the urban space through drains, working as a vector for disposal of waste from urban metabolism. Pipes, dams and reservoirs build invisible links of territorial scale and draw the extension of the city ́s ecological frontier, preserving upstream land from development to assure run off quality, and polluting water bodies that receive the effluent downstream.
Those pipes intertwine with territorial drainage lines to produce a new geography. flow of water integrates the city with its water basin. the continuity of watercourses, streams and dry riverbeds forms a delicate but relevant net of lines that goes through the multiple layer moire that forms the urban thickness.
Among the energy fields that explain water movement in the biosphere, two of them are the most relevant and linked with management: the one related with physical hydraulic power, (measurable according to mass and height over the sea level) and chemical, related to its composition and solution capacity. Vertical movement, due to evaporation by solar radiation, raises the water and removes dissolved substances. All the water states describe a potential energy field, that starts with rain, and descends to the sea, where it reaches its maximum entrophy level. These movements, that go through layers and connect ecosystems, activate an enormous variety of process as they go by.
Cities construction usually works as a landscape desertification process. Ground surface is paved, soils cannot retain rainwater that disappears very quickly from the environment, turning it dry and arid. Local watersheds lose their performance as run-off is managed by invisible underground pipes. Only occasional puddles, the result of system failures, enrich urban space with shine and reflections. However, under this impervious surface, thousands of cubic meters of diverse kinds of waters move through the soil, and interweave infrastructures and living systems to give rise to a particular phreatic, that transform regional scale aquatic dynamics. The underground is the amalgamation of all the externalization of urbanization.
Overlapping cartographies of different periods of a settlement development enables another approach to the understanding of urban hydrology. Urban patterns, street directions and topography acquire significance from the drainage lines previous to the sewers’ construction. Within historical centers, the transformation of the natural features during urban consolidation has been softer, therefore the original topography and soil qualities normally remain. Waterways have defined and conditioned urban fabric, interweaving with it. They have lasted as linear voids until today, sometimes transforming into traffic roads or freeways.
It is interesting to notice how the toponymy has fixed through words different states of the urban nature, in which water was part of the public realm. Names as Ribera de Curtidores, in Madrid, or La Ciénaga Boulevard in Los Angeles, openly refer to hydrology conditions. Blue
Road in Drachten, Holland, depicts at real scale this palimpsest. The blue line marks along 1000 mts the location of an historical channel, where a road can be currently found.
Banyoles is a town located at the shore of the biggest natural lake in the iberian peninsula. Traditionally water channels from the lake went through the town center to irrigate urban orchards and backyard gardens. In the course of time, as orchards have disappeared, the channels were progressively covered and used as sewers, losing the relationship of urban space with its surroundings by means of the water flow. The recently built renovation project recovers pedestrian and water circulation through the center.
Furrows sculpted in the surface of the new stone pavement give form to water glide. The irrigation system is now uncovered intermittently and eventually opened in bigger sections. Children can play as if they were in front of a puddle.
At metropolitan scale, the plan to restore London’s lost waterways pursues the same aim. The project ́s websiteiv shows an amazing interactive map of the local watersheds and the river Thames ́s tributaries that now flow in pipes under the surface. The plan includes multiple strategies within the whole metropolitan area to restore surface drains and waterways, turning them into a continuous system of outdoor public spaces and enabling water to reactive ground and air qualities.
By understanding the possibilities of ground surface morphology, from the layout of local streams, a richer imagination of urban space emerges, pointing out potential transformations to retain and visualize the enormous patrimony of local water and humidity that rain and run- off are. By watching gravity led water movement, we can identify foldings and ways defined by topography, and concavities that produce natural lamination. It also shows where spontaneous green could appear as a new “riparian vegetation”. Furthermore, opening underground pipes also activates vertical movements. Water infiltrates in the soil and nurtures autoctonous vegetation or evaporates into the air.
As David Gissen suggests, this approach can be framed into “a peculiar contemporary moment in which “reconstruction” is the modus operandi for politicized forms of environmentalism” and recovering hydraulic performance of the traditional city “marks an engagement or partial reconstruction of the city’s now-irrecoverable earlier form”. Hydrologic conditions have evolved as a part of the gradual construction of urban environment. Water ́s quality, volume and frequency patterns are different. Water tables have moved away from surfaces and enormous volumes of supplied water move through the underground.
This proposition for public space implies considering rainwater and run off as an asset for the city. Air pollution and pavement dirt (which include all kinds of stuff, result from urban metabolism) are swept by water, very far away from idealistic paradigms of urban nature, yet closer to the magic and syntetic carpet of delirious New York, or the corrupted biotopes of Francoise Roche. Toughness of urban environment requires the design of an optimized and technical nature, according to the water we have. Growing water envisions the transformation of
Chicago city center into a big treatment machine. linear eco-boulevards, integrated into urban grid, operate as a decentralized infrastructure. all the sewage and rainwater is treated as it flows through these lines, to enable its re-use or its return to Michigan lake, from where the city ́s supply starts. These landscape strips go from the water basin border to the lake shore. the treatment is made by microorganisms, plants and fish: hydroponic systems and ecological processes for sewage and wetlands as low energy filters for rainwater.
By integrating urban form and hydrological dynamics, overlapping public space and infrastructure, a project of a continuous net of outdoor spaces with new attributes: visualizing systems that support urban life and recovering “the productive surface” of the city. Mirko Zardini has emphasized the relevance of the asphalt in the transformation of the urban environment, taking away dust, mud and puddles, But this syntetic carpet is capable of much more. To involve the water flow and evaporation in the design of urban surface, would make possible the production of environments and different sensorial conditions. besides energy efficiency, it would intensify somatic experience, and create spatial effects and interferences with the numerous physical, environmental and termodynamic phenomena that take place around us.
1. Gandy, Mathew: “ the Paris sewers and the rationalization of urban space”
2. Williams R H 1990 Notes on the underground: an essay on technology, society and the imagination MIT Press, Cambridge MA
3. Alissa Walker photograph tour of L.A.’s original subway system, at http://www.gelatobaby.com/2012/05/11/las-original-subway/