Olası Marmara depreminde toplanma alanları yer seçim kriterlerinin belirlenmesi: İstanbul Bağcılar örneği
Site location criteria of refuge areas for possible Marmara earthquake: Case study of Istanbul Bagcilar
Yazar: DOĞA DİNEMİS AMAN
Danışman: DOÇ. DR. GÜLŞEN AYTAÇ
İstanbul Teknik Üniversitesi / Fen Bilimleri Enstitüsü / Peyzaj Mimarlığı Ana Bilim Dalı / Peyzaj Mimarlığı Bilim Dalı
Derece: Doktora, 2019
Konu: Peyzaj Mimarlığı = Landscape Architecture
Dizin: Kentsel yeşil alanlar = Urban green areas ; Marmara depremi = Marmara earthquake

Özet:
Günümüzde dünya nüfusunun yarısından fazlası kentlerde yaşamaktadır, bu nüfusun büyük bir çoğunluğu afet riski altındadır ve bu durum afet riskinin azaltılmasında kentsel alanlara odaklanmayı gerekli kılmaktadır. Alp-Himalaya deprem kuşağının içerisinde bulunan Türkiye, özellikle 1999 Marmara Depremi sonrası büyük bir can ve mal kaybı yaşamış, yakın gelecekte İstanbul'un da deprem riski altında olmasının bilimsel verilerle açıklanmasıyla yeni kayıpların yaşanacağı endişesi, rasyonel çözüm yollarının araştırılmasını gerektirmiştir. İstanbul, yaklaşık 15 milyon nüfusuyla dünyanın gelişmekte olan en önemli megakentlerinden biridir ve Türkiye'nin kültürel ve ekonomik anlamda en önemli kentidir. Ancak tarihsel süreçte birçok yıkıcı deprem yaşayan ve yakın gelecekte bir deprem daha beklenmekte olan bu kadar önemli bir kentin, depreme karşı dayanıklılığın artırılması her meslek grubu için göz ardı edilemez bir zorunluluk olmuştur. 
Depremler, yapıların yıkılması veya zarar görmesi nedeniyle insanların evsiz kalmasına neden olmaktadır ve barınma, deprem sonrası dönemde etkilenen insanların öncelikli ihtiyaçlarından biridir. Kentsel açık ve yeşil alanlar, afet anında ve sonrasında kişilerin barınma, toplanma gibi ihtiyaçlarının karşılanmasında önemli görev üstlenirler. Özellikle afet sonrasında altın saatler olarak adlandırılan ilk 72 saat süresinde, bu alanlar toplu tahliye öncesi kişilerin geçici olarak barındığı alanlardır. Deprem sonrası kişilerin toplanma ve barınma olarak kullandıkları açık ve yeşil alanların her geçen gün azalması, büyük bir sorun teşkil etmektedir. Ülke genelinde düzensiz kentleşmenin doğurduğu açık ve yeşil alan sisteminin olmayışı problemi,  deprem ve diğer afetler durumunda büyük risk oluşturmaktadır. Dolayısıyla bu konu afet yönetimi kapsamında ele alınmaya başlanmıştır. 
İstanbul kentinde yakın gelecekte beklenen deprem sonrası ilk toplanma ve daha sonrasında barınma ihtiyacını karşılamaya yönelik yeterli kentsel planlama stratejileri geliştirilmemesi kaynaklı riskler bulunmaktadır. Toplanma alanlarının temel amacı, afet anında insanların güvenliğini sağlamak için riskleri azaltmak veya ortadan kaldırmaktır. Afet anında veya sonrasında bu alanlar daha büyük riskler barındırıyorsa, afetten sığınmaya olanak sağlamak yerine daha büyük tehdit oluştururlar. Dolayısıyla bu alanların depremin yol açağı ikincil tehditlere karşı güvenli olması, planlama ve tasarım aşamasında en önemli meseledir. Tez çalışmasının amacı, afete hazırlık ve zarar azaltmada kentsel açık ve yeşil alanların rolünü anlamak, İstanbul'da depreme hazırlığı ve deprem zarar azaltmayı desteklemek için güvenli açık ve yeşil alan seçim kriterlerini belirlemek ve İstanbul'da kentsel ölçekte deprem toplanma alanlarından oluşan peyzaj altyapısı modelini üretmektir.  Deprem anında ve sonrasında kullanılacak toplanma alanlarının belli kriterler doğrultusunda yerlerinin seçilmesi, bu alanlarda can güvenliğinin sağlanması için gereklidir. 
Çalışmanın ilk aşamasında güvenli toplanma alanlarının yer seçim kriteri, literatür araştırması sonucu elde edilen veriler, örnek alınacak kentlerden elde edilen kriterler ve uzman ve depremzedelerle yapılan yüz yüze görüşmeler sonucu elde edilen kriterlerin değerlendirilmesi sonucu geliştirilmiştir. Çalışmanın ikinci adımında yer seçiminde kullanılacak kriterler belirlenerek karar matrisi oluşturulmuştur ve kriterlerin ağırlıkları hesaplanmıştır. Üçüncü adımda, İstanbul Bağcılar'da seçilen 7 mahallede açık ve yeşil alan analizi yapılarak potansiyel alanlar belirlenmiştir. 7 mahallede toplam 230 potansiyel toplanma alanı belirlenmiştir. Haritalara işlenen potansiyel alanların belirlenen kriterlere göre analiz planları oluşturulmuş, karşılık gelen puanlar karar matrisine işlenmiş ve kriterlerin ağırlıkları ile çarpılarak nihai puanlar elde edilmiştir. Elde edilen puanlara göre potansiyel alanlar en yüksekten düşüğe doğru sıralanmıştır. Yüksek puanlı toplanma alanlarından başlayarak mahalle nüfusuna göre yeterli büyüklükte alan sağlayacak potansiyel alanlar haritada işaretlenmiştir. 7 mahalle için toplam 107 toplanma alanı ve 85 cadde ve sokak tahliye yolu olarak belirlenmiştir. Her mahallede belirlenen toplanma alanları ve bu alanlarda toplanacak insanların can güvenliğinin sağlanması için, kriterlerin risk derecelerini belirten değerlere istinaden alınması gereken önlemler açıklanmıştır. Çalışma kapsamında 7 mahallede belirlenen toplanma alanlarının yeterliliklerinin saptanabilmesi için etki alanı analizi yapılmıştır. Son olarak deprem-güvenli kentsel açık ve yeşil alan kriterleri belirlenmiştir ve toplanma alanlarına yönelik bölgesel senaryo indeksi ve stratejik kesitler oluşturulmuştur. 
Gelecekte hızlı kentleşme, etkili bir şekilde yönetilmediğinde afet riskini artıracak açık bir tehdit oluşturmaktadır. Depreme neden olan tehlikeler tamamen ortadan kaldırılamayacağı için bu tehlikelerin neden olacağı zararların en aza indirgenmesi büyük önem taşımaktadır. Açık ve yeşil alanların deprem riski altında yaşayan toplumlarda toplanma ve geçici barınma alanı olarak planlanması kent ve toplum için sürdürülebilirliği artıracaktır. Afet zararlarını azaltma konusunda plancılar, toplanma ve barınma alanlarının yer seçimini belirleyen sağlam bir metodolojiden önemli ölçüde faydalanabilir. Tez çalışması, acil durum planlamasına, açık alanların uygunluğu ve bir deprem ardından toplanma alanlarının yer seçimine yönelik bir metodoloji geliştirerek katkı sağlamaktadır.

Abstract:
Today, more than half of the world's population lives in cities, the majority of which are under disaster risk, and this requires focusing on urban areas to reduce disaster risk. Turkey is located within the Alpine-Himalayan seismic belt and more than half of Turkey's population is living under the first and second degree disaster hazard. Turkey has spent tens of earthquakes in the past half-century and resulted in the deaths of thousands of people. Istanbul, one of the world's most important emerging megacities with 15 million population, Istanbul is Turkey's most populous province and is the most important city in social, cultural and economic terms. However, the city is situated near the North Anatolian fault line, has suffered many destructive earthquakes in the past and is expecting an earthquake in magnitude 7.4 in the near future. Therefore, increasing the resilience of such an important city has been a necessity for every profession.
Two major studies after the 1999 İzmit Earthquake showed the potential earthquake risk in Istanbul; the study of the Disaster Prevention / Mitigation Basic Plan in Istanbul including Seismic Microzonation by JICA-IBB and the Earthquake Risk Analysis of the Istanbul Metropolitan Area prepared by the Kandilli Observatory and Earthquake Research Institute of Bogazici University. Following these studies and the establishment of the National Earthquake Council and the publication of the National Earthquake Strategy Report in 2002, Istanbul Earthquake Master Plan was prepared in cooperation with four universities. These master plan responsible authorities have been pioneers in the preparation of a plan for disaster risk reduction and management.
Earthquakes cause people to lose houses because of the destruction of buildings and shelter is one of the vital priority needs of people affected by the earthquake. Urban open and green areas take on an important role in meeting the needs of people such as sheltering and gathering during and after the disaster. Especially in the first 72 hours after the disaster, these areas are the places where people are temporarily accommodated before the mass evacuation. It is a big problem that the number of open and green areas that people use for gathering and shelter after the earthquake is decreasing day by day. The problem of the lack of open and green space system, which is caused by irregular urbanization throughout the country, poses a big risk especially in the case of earthquakes and other disasters and has started to be handled within the scope of disaster management.
In the historical process, open and green space planning in urban disaster prevention is an important place in many urban histories. After the Great London Fire, restructuring plans are recommended, instead of irregular London streets, Wren proposed a drastic change in the streets as grand boulevards with gridal system. The first disaster prevention planning with public green space appears during Renaissance period. During the Renaissance period, some cities of countries such as Italy and Portugal, which have been in the earthquake zone, have switched to urban plans that have wider paths and openings than the medieval planes with their organic forms and narrow streets. Many cities such as Catania in Italy and Portugal in Portugal have been built in earthquake zones and in order to prevent and reduce the damage caused by earthquakes; people have changed the city's original order in the reconstruction plan after the earthquake. After the great fire in Chicago in 1871, it was once again the model for the wide boulevards during the rebuilding of the city, and a city park system was created to separate high density residential areas with parks and green roads to prevent the spread of fire and lead the green space system planning model. Other American cities like Minneapolis and Boston took example of the green space planning in disaster prevention.
There are problems due to the lack of adequate urban planning strategies to meet the need for shelter in Istanbul city in the near future for the first meeting after the expected earthquake. The main purpose of the refuge areas is to reduce or eliminate risks to ensure the safety of people during and after a disaster. If these areas present greater risks at the time of disasters or after, they pose a greater threat rather than allowing refuge. Therefore, the safety of these areas against the secondary disasters caused by the earthquake is the most important issue during the planning and design phase. The aim of the thesis study is to understand the role of urban open and green areas in disaster preparedness and loss reduction, to determine safe open and green area selection criteria to support earthquake preparedness and earthquake mitigation and to produce landscape infrastructure model consisting of earthquake refuge areas in Istanbul. The selection of the places to be used during and after the earthquake in accordance with certain criteria is necessary to ensure the safety of life in these areas.
The reason why Istanbul was chosen on the upper scale is the fact that it is located on the North Anatolian Fault, the possible Marmara Earthquake will be realized in the near future and the country will be affected greatly by the possible losses caused by this earthquake. The European Side and the south of Istanbul are under higher earthquake risk due to geological conditions and building stock. Bağcılar is one of the district locating in the European Side of the city and is under great risk. Especially the southern section of Bağcılar, which is close to the fault line, is under higher earthquake risk. Therefore, 7 neighborhoods located in the south of Bağcılar; Bağlar, Hürriyet, Barbaros, Kazımkarabekir, İnönü, Yıldıztepe and Yenigün are identified as the study area. The study aims to determine safe refuge area site selection criteria and to evaluate the potential open and green areas in 7 neighborhoods of Bağcılar district for a safe refuge area system. 
In the first phase of the study, the reason of an integrated method is given to investigate the site selection criteria of the refuge areas. In order to determine the criteria of site selection, literature review based on previous academic studies has been made as the basic prerequisite of the methodology. Afterwards, successful international cities were investigated in order to set an example for the city of Istanbul. The last step in determining criteria was interviews with experts and earthquake victims. The proposed methodology focuses on the selection and weighting of the criteria for site selection for emergency refuge areas. Therefore, the criteria were defined to investigate the suitability of open spaces in urban spaces for emergency gathering and shelter. The determined criteria are explained in detail and the range of points to be used in the evaluation of potential areas is given. 15 criteria were determined in total.
Lessons learned from Tokyo, San Francisco and Athens are used during forming the decision matrix for site selection criteria. Japan is located in Pacific Ring of Fire, the most active earthquake zone in the world. After Great Kanto Earthquake in 1923, Japan understood the importance of open and green areas in the prevention of natural disasters, and decided to separate the busy urban areas with open spaces such as parks and park roads in order to prevent the spread of the fire. With the law, the necessity of having the disaster prevention function of the parks has been established and standards have been set for the planning and management of urban parks. After the Great Kobe Earthquake in 1995, the streets around the building islands were expanded, open and green areas were increased after the earthquake in order to rebuild the affected areas and to respond urgently to future large-scale disasters. San Francisco is located near San Andreas Fault which is similar to North Anatolian Fault Line. After 1906 Great San Francisco Earthquake, people took shelter in tents established in parks. This showed the importance of urban green areas and the city identified potential shelter areas and these are ready to be opened. Athens is located in earthquake hazardous zone and faced several disasters in history, therefore an Emergency evacuation plan in case of possible earthquake is prepared for the city and some site selection criteria are explained. The main objective is to find out the maximum number and size of open spaces that allow the population to remain safe for short periods immediately after the initial shock.
In the second step of the study, the criteria to be used in site selection were determined and a decision matrix was formed, then the weights of the criteria were calculated. The criteria are more or less damaging than the potential risks they contain, so each criterion does not have the same importance in the site selection study. While some criteria carry more fatal risks, some criteria may be less hazardous. In determining the importance of the criteria, the criterion was measured to increase the probability of survivors' survival by protecting the collected disasters against secondary disasters until professional assistance was received. In the third step, open and green area analysis was performed in 7 selected districts in Istanbul Bagcilar and potential areas were determined. A total of 230 potential refuge areas were determined in 7 neighborhoods. In the forth step, analysis plans were prepared according to the determined criteria of the potential refuge areas. In order to create analysis plans, the maps produced in Istanbul European Side South Microzonation Study which was completed in 2007 by the Directorate of Earthquake Risk Management and Urban Improvement Department of Istanbul Metropolitan Municipality were taken as basis. According to the microzonation maps examined, three criteria out of the 15 criteria were found to be no risk in 7 neighborhoods in Bağcılar District, therefore, 3 criteria was excluded from the evaluation process. The corresponding scores were processed in the decision matrix and multiplied by the weight of the criteria and the final scores were obtained. According to the scores obtained, the potential areas are ranked from the highest to the lowest. The high-rated refuge areas are ranked from high to low according to the population of the neighborhood and the potential areas that will provide sufficient space according to the population are marked on the map. 
A total of 107 assembly areas and 85 streets and street evacuation routes were designated for 7 neighborhoods. In order to ensure the safety of the people to be gathered in these areas, the measures to be taken with respect to the values indicating the risk levels of the criteria are explained. In the scope of the study, domain analysis was conducted in order to determine the adequacy of the refuge areas determined in 7 neighborhoods. Finally, the criteria of earthquake-safe urban open and green area were determined and a regional scenario index and strategic sections for refuge areas were established.
In the future, rapid urbanization poses a clear threat to disaster risk if not managed effectively. Since the dangers that cause disasters cannot be completely eliminated, it is of the utmost importance to minimize the damage caused by these hazards. The main purpose of the refuge areas is to reduce or eliminate risks to ensure the safety of people during and after a disaster. If these areas present greater risks at the time of disasters or after disasters, they pose a greater threat rather than allowing refuge from disaster. The planning of the green system as a refuge area in societies under earthquake risk will increase the sustainability for the city and society. Regarding disaster mitigation, planners can greatly benefit from a robust methodology that determines the choice of gathering and sheltering areas. This study contributes to emergency planning by applying a methodology for site selection of potential open and green areas as refuge during and after an earthquake.