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Reclaiming Ecological Sustainability of Urban Streams by Use of Green Infrastructure Techniques
Urban water systems play an important role in the ecology by linking neighbour natural areas while they support a high density and diversity of riparian vegetation. However they are suffered from human activities such as urbanization and high concentration of population. Throughout the history, people have always chosen the places that are close to water. Easy transportation route for trade, good defence for enemies, fertile soil, moderate climate, navigation, social interactions can be considered as some of reasons. After settlements of people in these areas and urbanization, the natural section of urban streams started to change gradually. Natural habitats near to urban water systems were replaced by impervious surfaces. The destruction of river ecosystems by land transformation resulted in hydrologic changes and habitat changes. Land uses for retail, residential, commercial and recreational purposes in removed riparian vegetation had major impacts on landscape functions. After they have been seen as a flood threat because of uncontrolled runoff, municipalities and developers targeted watercourses and riparian communities and many creeks in urban areas faced to channelization and alteration and from functioning to prevent damage from flooding and to reduce pollutants carried into water and waste products. Since degradation of urban water systems have become an important problem for cities, restoration efforts of these water systems have been initiated in the world.
In general rehabilitation efforts for urban rivers has been implemented with the context of only river itself. Green infrastructure is seen as ecological framework needed for environmental, social and economic sustainability and it provides flood control, improved water quality, vegetation that controls erosion and stabilizes the soil on steep slopes. In this study, rehabilitation of urban rivers within a broader context by using green infrastructure techniques are explored. Principles of restoration and green infrastructure techniques, some of wrong implementations on watercourses, the best practices around the world, a case study from Izmir and the integration of stream restoration and green infrastructure will be discussed in this paper.
1.1. PROBLEM DEFINITION
It is generally agreed today that climate changes is caused by the interactions of atmosphere’s components. These components such as soil, water, wind, can be affected by interventions of human activities. As one of these components is damaged or affected, the others will be also affected in time because of being the ring of the same chain . People have not noticed these changes in climate so much until last 50 years since they were living closely to nature. Urbanization is considered as one of main reason of these changes. Abnormal increase in urbanization has caused climate changes and damaged ecosystems by human and consequently increased the number of floods. As a result of urbanization and concretization, surface flows are increasing, infiltration and underground levels are decreasing. Increased stormwater runoff overloads pipes and sewer systems and urban flows change irregularly and that damage water quality. These changes affect the flow of urban streams and flooding problems occur while pollutants, which are carried into the waters from a variety of sources including rivers, lakes and see, are increasing.
Impervious surfaces in cities, such as concrete or asphalt roadways or other paved areas, became one of main problems as a result of urbanization. Natural ecosystems are being replaced and destroyed by impervious surfaces. These surfaces are not able to absorb stormwater and that results in further degradation such as excessive erosion, loss of wildlife and pollution. When rainfall reaches to surface of cities, it evaporates, infiltrates into the soil or runs over the surface. If water cannot be infiltrated or evaporated, it is conveyed to large drainage systems such as creek, streams, rivers in the cities. After the reduction in the amount of natural pervious ground, it started a problem to convey easily. During heavy rains, accumulation of water on impervious surfaces makes the flow of water faster and this unnatural flow also damages the environment.
Furthermore, replaced impervious surfaces have also increased the distance between people and natural spaces. The competition for land use also resulted in a patchwork pattern. The isolation between patches leads to fragmented habitats. After all, most cities worldwide has initiated to revitalize their urban areas including urban water systems.
1.2. STUDY OBJECTIVE
- To assess the literature on understanding green infrastructure and urban river restoration
- To identify methods of utilizing green infrastructure in urban river restoration process
- To explore the integration of green infrastructure techniques and urban river rehabilitation process in an attempt to unify
- To examine the currents restoration systems in Turkey and to determine the success or failure of the system.
- To learn from mistakes made in past projects and to ensure administrative frameworks
- To provide information to municipal staff, planners, designers and decision makers.
- To develop guidelines based on case examples and a design framework at local level that can be used by planners, designers and decision makers
- To determine and analyse vegetative land use, land use changes, population changes, precipitation rates and water quality in the case study and to determine the correlations among them
- To minimize land fragmentation in the case study with the incorporation of green infrastructure techniques
1.3 RESEARCH QUESTIONS
- How green infrastructure techniques can be applied in the process of urban stream reclamation?
- What are the problems with urban streams and stream reclamation?
- What are the elements of green infrastructure and stream reclamation?
- Can a framework be established as a tool to for river restoration?
1.4. RESEARCH DESIGN
First part is the establishment of theoretical frameworks that includes definition of problems, assumptions, literature review on river restoration and green infrastructure. Second part is the definitions of terms and linkage of restoration and green infrastructure. Third part includes the best practices on river restoration and green infrastructure from all over the world. Fourth part consists of a case study from Izmir in Turkey. In this part, the site will be examined, the problems will be discussed and green infrastructure techniques will be implemented to rehabilitate the creek and its surrounding area. In the last part discussions and solutions will be presented.
1.5. RESEARCH METHOD
Grounded theory can be used in data collection for case study while making comparisons, asking questions, taking samples. It is an applicable research method for a design approach. Built upon grounded theory, a review of recent and relevant literature review on green infrastructure and river restoration will be done. Limitation of the study will be identified lastly in discussions part.