These functions, which constitute my definition of ecological integrity, take into account the Proper Function Condition. While the presence of all four is necessary for achieving success, some functions can only be achieved one at a time. Although the traditional stream corridor restoration approach (PFC) procedure defines streams without floodplains (when a floodplain would normally be present) as nonfunctional, many streams that lose their floodplains through incision or encroachment still retain ecological functions. The importance of a floodplain needs to be assessed in view of the site-specific aquatic and riparian community. In urban environments, it is likely that all or most of a stream’s flood plain will be lacking. Nevertheless, these ecological functions regroup the most characteristic features of streams and can be applied individually or collectively. While their combined presence greatly contributes to a stream’s ability to remain healthy, improved stream functionality can result the presence of one ecological function. Attention to water quality, for example, can lead to the development of marine life.

Urban Stream Restoration: Differing definitions, objectives, incentives

Urban Stream Restoration is a widely used term to describe numerous approaches to projects that involve work carried out on urban streams. While ideas of re-establishing the natural state of a stream or river are a common objective, many projects are not conceived with this goal in mind. Economic incentives are often the most persuasive in initiating projects. A restored stream is perceived as an infrastructure investment that can often attract new interest in a formerly neglected area, much like an urban renewal project can. In other cases, projects are initiated by triggers; factors that make the current state of the stream disadvantageous to the quality of life in a neighborhood.

Daylighting is a term used to describe projects that deliberately expose some or all of the flow of a previously covered stream. Although project objectives range, the removal of the stream from underground pipes and culverts usually aims to restore some of the form and function of the historic stream. This indicates that it is the most profound form of stream restoration, recreating a surface waterway where nothing exists now. Daylighting projects are carried out for numerous reasons, and often the restoration of ecological functions are not the motivating factor, largely due to economic reasons. Often they can only be achieved if a considerable economic rationale can be used to justify projects. Stream restoration becomes increasingly challenging as the amount of constituents increase. In a dense urban environment, it is not possible to accommodate solely plant and animal habitat, as the stream may also serve as a place for recreation.

The recent daylighting of Providence’s river was carried out as part of a downtown redevelopment district plan, which called for the creation of cultural programs along the stream. Unfortunately, ecological functions were not valued at all in this case, and consequently the city has a new urban amenity that does not fulfill its ecological role as a water body. Throughout the growing season, ashes from WaterFire are repeatedly released into the water, clouding the water and preventing marine life from developing. It could be said that to label such a project as restoration would be inaccurate: uncovering an urban waterway in itself is not a restoration; the accompanying practices that make the waterway resemble a true stream determine this.

While the term "stream restoration" indicates attention to re-establishing a naturalistic form, the details and incentives of each project do not always lead to this approach. Streams are restored for many different reasons, some of which have no ecological intentions. The following statement as issued by the United States Environmental Protection Agency concerning restoration work being done on the Chicago River:

Contrary to this statement, ecological integrity should be the ultimate objective of every urban stream restoration project, even if it is not the first priority the end result. To aim for greater integrity demonstrates commitment to making up for the damage humans have caused. "Restoration practitioners share simultaneously in the good fortune and responsibility of participating in a new endeavor —stepping beyond the current concept of natural resources conservation to a newer concept of restoring the living environment to an ecologically viable condition — to create places that improve rather than degrade over time." As natural systems, streams have this ability which would be beneficial to urban environments where degradation is natural.

Considering the challenges posed by dense urban environments, the following definition presents a realistic vision for urban stream restoration, applicable to any project:

This definition does not insist upon a return to the natural state of the stream, but accounts for the inevitable presence of humans in the environment. Projects striving to embrace this approach can achieve successful restoration within human-dominated environments. A successful urban stream restoration project should restore the ecological functions of the stream and its flood plain within the larger context of the watershed. Successful urban stream restoration should begin with the goal of eradicating the stream of all major human-induced nuisances. Reestablishing at least some of the stream’s ecological functions should be sought: continuous flow as part of a watershed, its hydrological cycle which accounts for the exchange between groundwater and stream flow and enables the stream to support marine life, and its vegetation cover along stream banks which provide erosion control and habitat. The opportunities for ecological enhancement are plentiful.

Assessing Several Projects of Urban Stream Restoration

Cities all over the world are rediscovering water. Since the end of the nineteenth century, economic and social practices directly linked to water have been progressively driven to ignore the ecological functions of urban streams and rivers. Local authorities have learned to manage them in a uniform manner or to cover them pure and simple for reasons of hygiene, protection against flooding, and space availability (urbanization, transportation infrastructure, parking, etc.) Today, certain cities are reconciling with their hydrographic network as recent realizations attest: opening of stream and river banks to the public, embellishment of quays, development of streambeds, and use of rainwater basins for leisure or elements of urban animation. The movement is the product of a general evolution of the politics of water that has had to integrate new concerns beyond the simple satisfaction of priority needs such as a healthy supply of water, protection against flooding or maintenance of public hygiene via evacuation of wastewater. The management of water has had to open itself to new demands and to new uses privileging everyday functions and quality of life (leisure, urban animation, nautical sports, etc.).

Most importantly, cities have had to take into account increasing populations’ demands on already overcharged hydrological systems. Weaknesses in these systems have been assessed while sustainable development practices become more and more common. Such practices focus on smarter use of resources, including the innate water filtration properties of certain plants. The following cases illustrate how ecological integrity has been a guiding force to restore urban streams. In light of the Bièvre’s restoration in Paris, they present two equally ambitious programs for reintroducing long-extinct natural systems into the urban fabric.

The Brook Concept in Zurich, Switzerland

The city of Zurich has historically been crossed by numerous mountain streams fed by snowmelt from the adjacent Alps. Although urban land uses lead to their demise as early as the eighteenth century, the streams originally provided habitat and charged the region’s water table. With the intense population growth of Swiss cities in the second half of the twentieth century, eleven suburbs were added to the city of Zurich alone. Nearly 100 kilometers of streams were diverted into the sewage system to accommodate new streets and provide space for development. As the sealing of ground surface increased, more and more flood disasters occurred as more and more water was diverted into the sewers. Zurich became a sterile city where all elements of nature and recreational areas were restricted to private gardens and public parks. The sewerized streams brought unpolluted rainwater into the purification plants which increased operational costs and diminished the efficiency of the water cleaning process.

The Brook Concept was initiated with a broad approach to daylighting the urban streams. Two different types of restoration approaches were used: recreating naturalized, unsealed channels where space permitted and open-air, sealed and canalized channels where the dense urban fabric prevented stream bank recreation. The latter were often placed in playgrounds and parks where space was available and where links to meadow-type nature were prominent. Conversely, canalized water courses were located in dense residential areas where streets and houses restricted space. These channels were strictly defined, though arranged stones provided habitat for plants and small marine life. These brooks were referred to as "not fast running water streams but natural brooks in a defined channel". Both types of brooks contribute to the specific character of the surrounding residential areas and testify to the concept’s attention to establishing a stream system. Each individual watercourse’s situation was analyzed to achieve a successful planning. Important factors are the amount of circulating pedestrian and vehicular traffic, the existence of pavements on walkways, and the location of trees and vegetation.

Attention to ecological functions is evident throughout this project. Despite the limitation of dense urban development, the brook concept has been successful in creating different spaces for flora and fauna, filtering storm runoff from entering the sewer system, and reconnecting parts of the city to its water table. Locally, a higher air humidity and air circulation was achieved, giving a comfortable temperature and reducing air pollution. In addition, the plants along the streams and the evaporation of water influence the climate in a positive way. "The bigger a city is, the more important it is that not only human beings live in it. Urban brook projects are one part of the efforts for the ecological enrichment in town."

This project represents a highly developed approach to urban stream restoration. The only downsides are that not all streams can assume the meadow format because of space limitations. The canalized form is much less conformant to ecological functions, with no exchange between the stream and the groundwater. Space limitations also prevent this system from being able to accommodate heavy storm runoff or flooding. The city’s traditional sewer system continues to be relied upon in this case.

Uncovering the Cheonggyecheon River in Seoul, South Korea

The Cheonggyecheon River in Seoul, South Korea originates in two mountains at the city’s edge before flowing into Seoul’s major river, the Hangang. As early as 1394, when Seoul became Korea’s capital, the stream’s ecological integrity was disintegrating as the result of human-centered interventions. Over the next six centuries, the stream was repeatedly dredged, straightened, and canalized to facilitate its use a sewer. With the escalation of pollution and flooding problems, the river was covered in the 1920s, used as a road in the 1940s and finally built upon in the 1960s. The elevated Cheonggyecheon Expressway was constructed in 1967 to provide an artery to connect the city to its outskirts. A solution to promote the city’s expansion, it was made possible by the absence of development in the stream corridor.

A plan to dismantle the expressway, which fell into disrepair after only a few decades of use, and uncover the Cheonggyecheon, was created by the city in the late 1990s. The result of a combination of a citywide interest in promoting ecological integrity and the need to do something with the deteriorating expressway, the project’s objectives were unleashed and promoted rapidly. Although the restoration has yet to be completed, the expressway has been disabled and stream partially uncovered.

The restoration calls for the daylighting of the stream’s entire five kilometer urban stretch. With the highway’s destruction, space will be created on either side of the stream for stream banks and recreational space. Plans call for the creation of vegetation alongside the stream and water quality within the stream suitable for marine life. According to the project director, "More important than anything else is the restoration of the ecology that used to be there. Life will be restored and the quality of the water flowing will improve as it will be purified in high quality water treatment systems coming from the Hangang River and underground." According to the project description, the three functions of the Cheonggyecheon can be defined as water-utilization, flood control, and environmental protection.

In addition to environmental objectives, the project aims to incorporate historical elements into the new stream course, such as the conservation of a few pieces of the destroyed highway which are symbolic of the expressway in the modernization of Korea. The project is expected to create a major new tourist destination, as well as a popular recreation area for Seoul residents. Further, it is expected to attract considerable commercial investment at the cost of displacing a portion of the historically disadvantaged population currently residing there.

Despite its intent to establish some form of ecological integrity in the heart of Seoul, the plans and literature describing the project show more attention to creating an urban park and open space than to integrating ecological functions into the city’s infrastructure. The fact that no water remains in the streambed beneath the expressway is the project’s greatest challenge and opportunity, but the plan calls for the diversion and purification of water from another river into the Cheonggyecheon. The clean water is essential if the stream is expected to serve as recreation and habitat which will be added to the stream in the form of fish. With regards to the criteria for successful urban stream restoration, continuous flow as part of a watershed will not be achieved, although the hydrological cycle will be partially fulfilled with some exchange between groundwater and stream flow. Marine and wildlife habitats will be established with water quality control and vegetative stream banks, the latter also serving as erosion control and pollution filtration. Although the Cheonggyecheon Restoration Project does not fully execute all ecological functions, its focus on reestablishing the original state of the stream is noteworthy.

The Vieille Mer in Seine-Saint Denis, France

The Vieille Mer originates in the Oise River Valley northeast of Paris and traverses the low-lying areas of the département of Seine-Saint Denis. Fed by several smaller streams, it ultimately serves a catchment basin of 200km². This area, known as the Plain de France, was originally marshy until the stream was slowly transformed into an open sewer. Artisan, industrial, and urban activities developed though the turn of the twentieth century, occupying the stream’s banks and exploiting the flow of water for energy and waste release. As urbanization continued, the stream became incommodante, or inconvenient, and was covered in the 1960s. It then became an outlet for rain water runoff, transporting water and pollutants along its six kilometer stretch before its confluence with the Seine.

The Vielle Mer of today is covered along 95% of its course. The regulation of its flow has improved over the past few decades with rain water collection in retention basins and the creation of a separate sewer system for runoff and used water. Runoff is no longer released directly into the stream, but treated at a purification plant. With clean water flowing in the covered Vieille Mer since the 1990s, the Regional Council of Seine-Saint Denis has become interested in daylighting the stream. Early feasibility studies showed that the stream was never embanked and built upon, reducing the difficulty of uncovering it and its capacity to support ecological functions.

Preliminary plans for the Vieille Mer involve the uncovering of the stream along its entire stretch with the exception of the infrastructure crossings that will be maintained. As some places are more constrained than others, the stream’s width and treatment will vary from narrow, concrete-sided portions to much wider, naturalized stream beds. This latter treatment will provide the greatest opportunities for plant and wildlife habitat, but the plans also depict plantings within the concrete sections.

With regard to the criteria for successful urban stream restoration, this treatment will accommodate most of the ecological functions. First and foremost, the stream’s continuity will be reestablished between the treatment plant and the Seine. While this will provide a continuous habitat for all marine life, it will not reconnect the Vieille Mer to its entire network of streams. The treatment plant’s location prevents untreated waters from northern communes from joining the Vieille Mer, and thus restricts greater continuity. The project will, however, provide for other aspects of the hydrological cycle, notably the movement of water through air, soil, plants via evaporation-precipitation-absorption. This exchange between groundwater and stream flow is imperative to establishing habitat for fish and wildlife. Lastly, the sanitation system in creation since the early 1990s will provide for pollutant filtration and erosion prevention. Although this is the only aspect of the project to be realized, the proven feasibility of the others and the government’s dedication to them makes this a promising project.

The attention to ecological functions in all of these projects is indicative of successful urban stream restoration projects. While other examples of urban stream restoration exist, very few compare in magnitude to these two projects. The previous state of the streams within very densely settled environments make them comparable to the plan to reestablish the Bièvre in Paris. Discussion of the plans for this project in Chapter Four will reexamine the similarities and differences of these projects. Other cities are also contemplating the daylighting of their urban streams, but no others have reached the implementation phase. Several daylighting projects have been carried out in American cities, such as in Denver, Colorado, but these projects are most often found in suburban or low-density urban environments, where space is available to re-open a stream corridor. The challenge of reintegrating an ecologically functional stream within the extenuating circumstances of an urban environment will be explored in greater detail throughout this thesis.

Ecological Potential for All Urban Streams

This chapter demonstrates that ecological integrity, as defined by the presence of ecological functions, can be achieved in varying degrees within a dense urban context. The aspiration to integrate ecological functions and to think creatively instead of favoring past approaches are crucial to success. Although cities remain equipped to deal with water in the conventional way, this should not preclude change. Developing countries in many ways are fortunate to not have been subjected to twentieth century urbanism. Modern civil engineering may be capable of mastering humans’ desired intervention on the land, but current practices do not aim to create new environments that improve rather than degrade over time. Now is the time for new, ecological approaches to formulate and set precedent for a new, more sustainable urbanism. Streams and rivers can be restored for various reasons such as economic development while still accommodating ecological considerations. Since ecological integrity is not in contrast with the qualities that make a water environment pleasant to humans, its integration is highly feasible. The urban design is challenging, but not unattainable. Preliminary study of exemplary cases indicates that the ecological functions of a stream and the inner workings of an urban environment are not mutually exclusive.

Certain criteria are easier to achieve than others. The most difficult criterion is the reestablishment of a stream’s former continuity. Reconnecting any water course to its tributaries and sources requires land availability that is hard to come by in densely settled urban environments. Some marine habitat can be established with minimal water quality, but most life is contingent upon the provision of a range of species within the same food chain. This may be gradually achieved, however, starting with plant species that can live in the most polluted water. In retention basins, for example, reeds often thrive off of nitrogen-rich water. Their consumption of nutrients that are toxic to other life forms allows other plants and animals to develop.

All urban streams should preliminarily be treated with the same criteria for restoration as non-urban ones. Despite the added difficulty in integrating a naturalized stream corridor, some ecological functions are attainable. Exploiting the beauty of flowing water as solely an aesthetic element without considering its hydrological cycle or habitat potential is not successful stream restoration. Streams have greater purposes to serve than as places of leisure and recreation or as ideal locations for commercial centers. To not take advantage of the ecological functions of a stream is to ignore its true potential. Streams in cities should improve the flow and sanitation of water. Ecological integrity is not often the first priority, but it can become the ultimate goal as the project moves along.

The next few chapters will examine the restoration of the Bièvre stream in Paris, France, and its approach on incorporating ecological functions. Before analyzing the details of recent restoration efforts, it is important to consider the environmental history of the stream. Chapter Two will describe the perpetual exploitation and gradual destruction of the stream’s ecological functions over two millennia.