Back to the surface – Daylighting urban streams in a Global North–South comparison

Abstract

Many urban streams have vanished from the surface as a collateral effect of urban growth. Often, these buried streams have been forgotten, and only street names remind us of their existence. Reasons for stream burial include the gain of space for road or house construction or the use of stream water to transport wastewater. Today, restoration efforts to bring back fully canalized streams to the surface and to restore their stream bed (so-called daylighting) are being increasingly integrated into urban blue-green space planning, recognizing the high ecological and social value of urban streams, especially to support resilience against climate change impacts in cities. In this paper, we briefly revise the impacts of stream burial, present a series of case studies of daylighting from Europe (France, Switzerland, and Germany), and compare them with case studies from Asia (China, India, Taiwan). We found that high real estate prices, limited buffer riparian zone and resistance by the inhabitants were the greatest obstacles to stream daylighting projects. In contrast, economic gains from separating wastewater from rainwater and revival of cultural linkages with water were the strongest drivers to restore these streams. We then present methods on how to identify buried streams as candidates for daylighting and deliver criteria to select the most promising candidates. Acknowledging that each restoration project requires to be adapted to the local biophysical and local setting, we deliver a preliminary decision support system and a guideline for identifying the best candidate streams for daylighting projects, including the arguments in favor of restoration, the caveats, the social processes of decision-making, and perspectives for the integration of stream daylighting into urban climate change mitigation and adaptation concepts, in a Global North-South comparison.

A Socio-Ecological Approach to Conserve and Manage Riverscapes in Designated Areas: Cases of the Loire River Valley and Dordogne Basin, France

“…However, we are fully aware of the problem that solution approaches can not be copy-pasted from one site to another. The social structure (and thereby, the decision-making process), the biophysical setting (thus, the precise type of the problem(s) to be settled), the political setting (local to transboundary), and the societal "zeitgeist" (corresponding to the interest of the society in the proposed solutions) may differ considerably, as we discussed in the context of urban waterbodies and stream daylighting [52]. A comparison of success stories of projects, taking into account these four "spheres," may help to gain inspirations for innovative problemsolving in specific sites, and represents a beginning of translational, transboundary, and transdisciplinary research, which is urgently needed to speed up the transfer of solutions from one site to others.…”

“…In the case studies, the practical experience of the site managers (resulting from the interviews) was complemented by the results of literature surveys. This mixed approach is an efficient tool to overcome the restrictions of both methods (lacking scientific rigor in the reported experiences and lacking spatio-temporal coverage in the scientific studies) and overcome methodological hurdles in inter-and transdisciplinary studies [40,52]. The content analysis of the interviews with different site managers allowed us to systematically analyze their statements.…”

River culture: How socio‐ecological linkages to the rhythm of the waters develop, how they are lost, and how they can be regained

“…Support for the re‐establishment of the memory of disappeared water bodies may come from sources that are not very common for restoration scientists and engineers, such as ancient street names, interviews with older people, historical maps, or novels. In the context of daylighting (i.e., deculverting) of urban streams, this approach has proven to be very useful to rediscover the original course of the streams (Wantzen et al, under revision; Khirfan et al, 2020) and to re‐establish memory. In analogy to the ‘Stolpersteine’ (stumbling stones, small bronze plaques embedded in the pavements) bringing back the memory of Jewish people that used to live in European cities before the Holocaust (Drozdzewski, 2018), memorials to the physical existence and the ancient cultural linkages to water bodies may help the de‐novo development of a sense of place and become a driver for future restoration projects.…”