Transformation of streams in Istanbul and the impact of landuse

Green spaces are among the important indicators of urban quality of life worldwide. In addition to the recreational opportunities that they provide for the urban inhabitants they help to preserve the hydrological systems, the watersheds while also providing corridors and greenways to link habitats. In Istanbul the natural structure of streams is being changed and lost as stream beds are treated as cheap residential land. It is overlooked that green space with "water" is a valuable asset. Land use decisions and their applications usually do not prioritize nature. In most contemporary cities around the world, the natural structure of the streams is protected or if their structures have been damaged, they are reintegrated into the city life by putting them into their original form and thus providing a balance between ecology and economy. Cities have been refreshed, the life of the city dwellers have been restored while the streams have been included back into the citylife with their various natural, physical and aesthetic features. Streams have become important components since they provide for the existence of natural life, they meet recreation needs of city dwellers, they form the biological chain, they form the physical green band of cities, they are borders between places and they are aestetical components. A stream is a whole system with its valley bed(with flowing water and dry stream branches),its basin its skyline (which is formed with the combination of the top levels of the valley) and natural habitats such as flora and fauna. When this fact is forgotten and streams are considered seperately, its branches, its source and watershed change and disappear through various interventions. Stream basins, which are natural ecological corridors, are left outside planning considerations. They have been ignored under the pretext that there are no large river systems in Istanbul. These facts and approaches against the protection of streams (such as stream improvement techniques which are performed with concrete or stone materials and covered and/or uncovered systems) show that the importance of streams is not understood at all. This thesis aims analyse and demonstrate the dynamic structure of the streams in Istanbul with the purpose of providing planning tools to preserve and restore them with their natural structure, to make them part of the city life. The research examines the transformation of the physical structure of streams with various interventions to find out the size and extent of the damage caused in their natural environment. In this research, first the historical interaction between the urban macroform of Istanbul and its streams which are located outside the drinking water drainage basins of the City has been summarized. Then the relationship between the change of physical structure of streams and landuse has been analysed, the problems have been identified and the results have been evaluated. Results of the analyses at macro scale A stream basin is a dynamic open system a section of land drained by a stream and its branches. The streams outside the Drinking Water Drainage Basins in Istanbul have been analysed as "stream systems".The relationship between the basin bed, its ridgeline and its highest point form a basin system. Streambasins that are attached with common watersheds form "a system of stream basins" that are called as "Upper Level Stream Basins"(ULSB). According to the analyses performed at 168 stream basins, it has been discovered that the streams outside drinking water drainage basins in Istanbul are part of 23 upper level stream basins with a common summit. On the European side there are 13 upper level stream basins (%57) (Çilingöz, Kuzulu, Düzdere, Terkos, Karadeniz Avrupa, Baltalimanı, Kuzey Haliç, Güney Haliç, Ataköy, Küçükçekmece, Ambarlı, Silivri, Büyükçekmece upper level stream basins). There are 10 upper level stream basins on the Asian side (İsaköy, Kabakoz, Darlık, Riva, Ömerli-Paşaköy, Paşabahçe, Elmalı-Göksu-Küçüksu, Kadıköy, Tugay, Tuzla). It has also been discovered that streams form 5 United Upper Level Stream Basin (UULSB) being gathered in the sea, lake, bay and strait according to the feature of their mouths. They are the 1)Black Sea,2) the Bosphorous, 3) the Sea of Marmara, 4) the Golden Horn and 5) Lakes Büyükçekmece and Küçükçekmece (UULSB). • Stream basin system consists of a stream basin, its upper level stream basin and the united upper level stream basins. • A stream basin is a whole system with its valley bed with flowing water and dry stream branches, a drainage system working with its watershed and an ecological corridor. • The relationship between the united upper level stream basins and the upper level stream basins is a complete basin system with reciprocal transactions from one to the other. This relationship enriches the topography, the skyline, the shape and the landscape of the area greatly. The number of upper level stream basins and the number of united upper level stream basins constitutes the morphology of the basins of the area, their natural landscape and their original ecosystem. This formation presents various opportunities such as microclimate, habitat richness, natural view. These features are identifying criteria for the landuse. • The basins attached to each other constitute the ridgelines of the streams and the common summit identifies the united upper level stream basins. This relationship defines the natural and physical structure of stream basins. The system of stream planning works according to perpendicular planning levels from micro scale to macro scale or(vice versa) from macro scale to micro scale. • A stream and its basin, which are the smallest components, constitute the inner ecosystem with its own microclimate and natural structure and the united upper systems become components of larger ecological systems and biyom. The transformation of streams at microscale The analysis of the impact of landuse decisions on the transformation of streams has shown that 21%(703.428 m.) of the total length of the streams outside the Drinking Water Drainage Basins in Istanbul(3.344.417 m.) flows through the urban area and 79% of it (2.640.935 m.) flows through the countryside(forests, agricultural area and green areas). According to the results: • Landuse has influenced the transformation of streams directly. • Transformation of streams differs in urban and rural areas. • Transformation of streams changes through the developments of landuse decisions and residential density. • The determinations according to the 2007 plans showed that 33 streams (20%) out of 168 streams are outside the residential areas. These are 10 streams on the European Side; Muşmula, Karaman, Dere 1, 2, 3, 4, Taşlıbayır, Darboğaz, Sipahi Streams which flows into the sea of Marmara and 23 streams on the Asian Side; Beykoz MA 1,2, Boyraz, Çamaşır 1,2, Poyraz, Büyük Çakal, Küçük Çakal, Yağ, Büyük Kum, Küçük Kum, Çan, Adaklar, Partal, Kabafındık Ağırın, Köprücek, İsmail, Çoturpınar, Çukurtarla, Soğanlık, Haydarlı, Pelitli. • Stream typeologies consist of 1) natural, 2) covered, 3)uncovered and their various combinations. The impact of land use at the longitudinal section varies these combinations. These are natural, covered, natural+covered+uncovered, covered+uncovered, natural+covered, natural+uncovered combinations. • 36% out of 168 streams that have been examined are natural streams; 16 % of them are covered, 5% of them are natural+uncovered flowing streams, 10% of them are natural+covered flowing streams, 9% of them are covered+uncovered flowing streams; 24% of them are natural+covered+uncovered flowing streams. That means there are six different types of streams. These are natural, covered, natural+uncovered, natural+covered, covered, covered+uncovered, natural+covered+uncovered systems. • Uncovered flowing streamsystems are not seperate systems since they are the combination of natural and covered systems. They make different combination of natural and covered systems. They make different combinations with other systems. Uncovered system has not been determined from source to mouth. • 48% of physical structure of Istanbul streams has a combination system which consists of all three forms. There are natural, covered and uncovered systems at the longitudinal section. • 60 streams(about 36%) of 168 main streams in Istanbul have preserved their natural structure from source to the mouth. • 64% of the streams in Istanbul have lost their natural structure because of various land use applications. To conclude, streams are the smallest components of the whole system of stream basins, upper level stream basins and united upper level stream basins. Upper level stream basins which are next to each other shape the silhouette of the coastline and united upper level stream basins which consist of these basins constitute the whole system. This system of streams is further combined with the upper level ecosystems of the regional, continental and intercontinental levels. The determinations have shown that streams are also used as borders(e.g.private property bordaries, administrative boundaries). Stream line and its neighbourhood has been more attractive than the other parts of the basin while locating residential areas. This situation has caused the transformation of land along and around the streamline. At the longitudinal section the confusion of authourity and various landuse decisions have transformed the stream lines into mainly residential areas. This situation has demonstrated that neither the longitudinal section nor the transversal section of streams should be used as borderlines. The ridgelines of the streams should be used as borders. This also provides protection of the ecological corridors and the natural silhouette. A basin protection zone border is essential to protect and maintain the stream corridors. This second border is upper level stream basin border to observe ecological corridors and habitats. It has been determined that stream protection line has not been understood and identified in practice. The connection between streams and green spaces in the residential areas (all of the covered streams), the relationship between the streams and the city or the standard setback distance in the regulations have not been considered sufficiently in practice. It has been determined that each stream is in relationship with its basin and at the same time each stream is in relationship with its upper level stream basin and united upper stream basins. It has also been discovered that each stream has its own transversal section of flood plain, its special topographical and ecological features. The flood levels and precautions against flood risks of each stream(dry streams included), which are identified by the topography and natural structure of the stream itself, are different. This stream protection line must be developed as green areas which have been identified in quality and quantity in the lejands of the plans. The determinations at the macroscale affect the transformation of streams at micro scale. Streams can be evaluated in three different stages when they are examined according to the plan scales; a-The scale of streams and stream basins is 1/1000. It consists of the design, application, suppervision and management of watersheds and biological corridors. b- The scale of Upper Level Stream Basins is 1/5.000. Landscape planning starts at this stage and the silhoutte plan, life corridors and construction setback zones are combined at this scale. c- The scale of United Upper Level Stream Basins is 1/25.000. This is the upper scale level that transfers main corridors to 1/100.000 scale and at the same time it includes administrative and technical regulations. The results of the research have shown that streams are not independent components and that legal regulations about streams must be evaluated within the context of their basins. The relationship between stream basin systems and planning must must be understood clearly so that the ecology-finance balance can be provided to protect the natural structure of streams from urbanization pressure and reconnect the city and its citizens.