Turkish Water Institute and Istanbul Technical University1, İstanbul Technical University2
The world's population is concentrated in urban areas and urbanization became a dominant demographic trend as well as an important component of global land transformation (United Nations, 1993). On the other hand, in addition to its global reach, growing populations, changing consumption patterns, expansion of built-up areas and current low-qualified living of urban contexts are seen as unsustainable development patterns in the long term (Karr, 1999) with a number of documented effects on urban ecosystems. In particular, riverine systems as one of the most vulnerable components of urban ecology are exposed to the crisis of ecological deterioration with the acceleration of urbanization. In this context, this paper focus on the interactions between riverine systems and urban areas including the role, importance and functions of riverine systems as well as the threats and problems they have been confronting for the last decades. Therefore, the potentials for 'Renaturalization' of buried riverine systems by using 'Stream Daylighting' method is evaluated through several case studies and Ayamama Stream in Istanbul, is analyzed under the context of Co-MISDAL Model developed in this research.
Introduction: Due to increasing anthropogenic activities in urban areas, the functions of urban riverine systems have been gradually weakened; channels were polluted, buried and the riverine characteristics have been lost. All these negative effects on riverine systems emerged the term of 'Urban Stream Syndrome (USS)' (Walsh et al., 2005) which is characterized by geomorphic and hydrologic alterations on riverine systems and decribed the consistently observed ecological degradation of waterways (creeks, streams, rivers) draining in urban areas. The conflict between riverine systems and human interfere with the growing pressure of urban development dynamics urges to investigate for a sustainable solution for a couple of reasons; such as increased flood risk, access to fresh water, climate adaptation, increased socio-cultural needs and so on. On the other hand as a result of the weak interactions of ecological systems in urban areas, this research seeks for better tools and solutions to support healthy riverine systems through a comprehensive rehabilitation method in urban areas. Herein, the notion of 'healty river' requires thinking of a river as an ecological system, not merely a channel that conveys water from one origin to downstream (Changming and Xiaoyan, 2008). The definition considers the system integrity and continuity specially for maintaining ecological processes of aquatic habitats and community of organisms. It also provides a basis for renaturalization of degraded riverine systems. From this point of view, main focus of this paper is determined as 'Assessing Stream Daylighting Approach as a tool for renaturalization and integration of damaged and buried riverine systems into socio-economic and ecological systems of urban areas with a focus on providing mutual benefits and sustainability of natural and built environments'.
Methods/Materials: The methodology of the paper is based on descriptive analyses and conceptual reviews including three components which is formed by literature reviews, conceptual model development and case study application. Literature reviews as the first part of the research process, consists of several research questions, which conducts the organization of data along the whole research. At the second stage, a comprehensive approach is used to develop a sustainable model for the integration of urban and riverine systems. Determination of the problems of selected case studies are used to identify the conceptual model for the reflection to the Ayamama Case Study at the last stage. According to the literature reviews, several scientific databases (e-books, scientific articles, proceedings etc.) are overviewed and ten implemented stream daylighting projects are selected from four different geographical regions with their different social, economic, legal and environmental backgrounds. These cases have been assessed under 8 key themes to clarify the potentials and strengths of 'renaturalization driven stream daylighting' implementations on buried riverine systems in urban areas. The key themes are determined as: Primary goals and scope, drivers; feasibility, public participation, stakeholders and funding, legal background, positive impacts and results. The assessment of case studies under common themes, has provided a wide spectrum and a common background to analyze stream daylighting approach. This assessment process has facilitated the diverse aspects of the subject clarified as well as guided future development policies in regards to urban riverine systems.
Results and Discussion: As a result of the literature reviews and descriptive case study assessments, the 'Conceptual Model of Integrated Stream Daylighting (Co-MISDAL)' is developed. The model can be used as a tool for a better understanding the functioning of riverine systems and serve as a guideline for future studies and practices related to retrieval of lost and damaged systems especially in highly urbanized areas. The model also constitutes a common platform for facilitating the communication among different disciplines and determining key drivers and mechanisms within the main framework including set of indicators, which are essential for a successful implementation. In that sense, Ayamama Stream in Istanbul is selected as a case study area due to its critical location and situation.
Conclusion: Ayamama Stream is identical with many urban riverine systems in Turkey being under the pressure of human activities like industrial, commercial, engineering structures, urban land reclamation etc. In recent years, increased flood problems and damages caused communities to be aware of the existence of riverine systems in urban areas as an entirely living system. From this point of view, the Watershed of Ayamama Stream is analyzed in terms of its physical and social characteristics including land use/land cover patterns and spatial changes under the perspective of problems and potentials of the entire watershed area. Analysis of land use patterns demonstrated the high rates of impervious surfaces in the watershed. This result indicates the significance of the urbanization problem in the watershed and necessitates a comprehensive improvement approach in order to provide the long-term balance between development and stream-bank conservation in the entire watershed in terms of socio-cultural, economic and environmental aspects. Therefore, Ayamama Stream is adapted in to the model development process by assessing the drivers of the current problems of the stream, response of societies including rehabilitation projects and assessment of the watershed configuration for a daylighting implementation under the eight key themes of Co-MISDAL Model. 1. Changming, L. and Xiaoyan, L. (2008) Healthy River: Essence and Indicators, Journal of Geographical Science,63 (7) 683-692.
2. Karr, J. R. (1999) Defining and Measuring River Health, Freshwater Biology 41, 221-234, University of Washington, Seattle, USA.
3. United Nations, (1993). Human Development Report, Oxford University Press, Available at http://hdr.undp.org/en/media/hdr_1993_en_contents.pdf
4. Walsh, C. J., Roy A. H., Feminella, J. W., Cottingham, P. D., Groffman, P .M., and Morgan, R. P., (2005) The Urban Stream Syndrome: Current Knowledge and the Search for a Cure, Cooperative Research Centre for Freshwater Ecology, Water Studies Centre and School of Biological Sciences, Monash University, Victoria, Australia.