Not: Figürlerin, Tabloların ve Formüllerin daha yüksek çözünürlüklü görüntüleri için görsele sağ tıklayıp “resmi yeni sekmede aç” seçeneğini seçiniz
Ahmet Samsunlu, Aysegul Tanik & Veysel Eroglu
ITU, Istanbul Technical University, Faculty of Civil Engineering, Dpt. of Environmental Eng’g, 80626, Maslak- Istanbul /TURKEY
Within the framework of this paper, first the urban impacts on the existing infrastructure of a megacity, Istanbul is mentioned. Rapid population increase, illegal settlements and illegal urbanisation cause the existing infrastructure to be insufficient. However, great efforts are continuing on completing the infrastructure. Secondly, the probable effects of earthquakes on the existing infrastructure is emphasised based on the extensive experience gained in the last earthquake occurred at Kocaeli. Urgent precautions concerning infrastructure are listed.
KEYWORDS: Earthquakes, infrastructure, Istanbul, megacity, urban impacts.
Between 1990-2025, the number of people who live in urban areas is expected to double too more than 5 billion people. Almost all of this growth will occur in the countries of the developing world, (World Resources, 1996-1997). As centres of population and human activities, cities consume water resources from both near and distant sources. They also generate wastewater that is disposed of both inside and outside the city. In the process, urban areas generate environmental problems over a range of spatial scales: the household and workplace, the neighbourhood, the city, the wider region and the globe, (Linares et.al. 1993).
Urban environmental problems also create a range of social impacts. They may impair human health, cause economic and other welfare losses, or damage the ecosystems on which both urban and rural areas depend. Most urban environmental problems entail all three of these impacts, either directly or indirectly. In general, the healthiness and well being of a city basically depends on the status of its infrastructure. This most common and frequently observed urban environmental problem of the 20th century is faced in the metropolitan areas of the developing countries such as Cairo, New Delhi, Karachi, San Paulo, Mexico City, Beijing and Istanbul. The higher level of environmental pollution due to insufficient and improperly functioning infrastructure caused in these megacities is basically due to rapid population increase through migration from the other parts of the countries and thus to illegal housing and urbanisation. The basic reason of migration is expectation of humans to live in better situations in megacities by earning better compared to the conditions prevailing in rural areas. For example, within the past 30 years, the average population increase in Turkey was varying between 2.5% – 1.6%, whereas in Istanbul this increase varied between 7% – 4.6%. This paper will in particular emphasise on the impacts of urbanisation, followed by the probable effects of continuous earthquakes occurring in the nearby regions of Istanbul on the existing infrastructure.
URBAN IMPACTS ON INFRASTRUCTURE
Urban areas affect the environment through three major routes: the conversion of land to urban uses, the extraction and depletion of natural resources, and the disposal of urban wastes.
As cities expand, especially agricultural land such as forests and wetlands are transformed into land for housing, roads, and industry. Domestic and economic activities in cities require resources far in excess of what the local area can supply, so cities must draw their essential supplies of food, fuel, and water from distant places. The concentration of wastes in cities is much higher than that living in the countryside, living in a relatively small area and their greater levels of consumption.
Healthy Environmental Development of Megacities
Healthy development of cities depend on preparing and actualisation of country based planning, regional urban planning and on environmental arrangement planning as well as on the obedience of these planning schemes in all activities including economic facilities. If this planning approach and its obedience is satisfied, there will be no possibility of establishing of such megacities as the population, population density and industrialisation will be distributed equally all around the country. In Germany – which is a developed country with a total population of 80 million – the total population of its first three large cities, Berlin, Hamburg and Munchen is approximately 6 million. On the other hand, Turkey – which is a developing country with an overall population of 63 million – has a total population of around 20 million in the first three large cities, namely Istanbul, Ankara and Izmir. This reality indicates that approximately 40% of the urbanised population live in these three metropolitan areas. In countries where population density varies significantly, the main problem is the slowness of preparing the municipal plan controlling development and construction within a city and city plan for regulating the city’s development. Even if such planning activities are fulfilled in time, the over migrating population makes the job quite difficult to arrange vacant land for settlement. The economic weakness of the migrating population, their wish to continue their rural standard of living in the urban areas have led them to construct their houses in public land (in land not belonging to them), in a random and illegal manner especially in the suburbs of a city. These random settlements and such suburban areas are usually at the outskirts of the city where all types of urban infrastructure services are difficult to handle.
In developed countries, the development of cities is not performed in the prescribed manner. The urbanisation is realised according to the prepared city and municipal plans. Required land is spared for new housing and settlements where all infrastructure services including sewage collectors, drinking water supply systems, electricity and communication connections, solid waste collection and disposal services are fulfilled prior to settlement. In developed cities the population increase is not that much significant as faced in developing countries. The insufficient infrastructure services usually lead to serious public health problems. In 1958, a survey on public health was performed in Hannover and Istanbul. The result was quite amazing. Cholera and typhoid diseases were observed in both cities, where their comparison indicated the ratios of 1: 12 and 1: 20, respectively.
Saturation population of Berlin City was calculated as 6 million. However, its present population is approximately 3.5 million. All the water resources were arranged according to the needs of saturation population. On the other hand, environmental awareness among the inhabitants led to lower water consumption compared to old days. The current consumption is around 100 Lt/cap. /day whereas it was around 160 Lt/cap. /day previously. The infiltration losses in piping systems also decreased significantly (presently, it is around 3% in Berlin; World Standard is given as 5 – 15%; Turkey’s overall loss is around 65% and of Istanbul it decreased up to 35% from 50%) leading to even lower water requirement. Therefore, there is an excess of water supply to the city. The authorities are now on the way to sell their excess water to gain money. Another environmental problem of this city depends on the water supply again. After the World War II, due to the economic constraints of the country, basement foundation of the houses were not sensitively isolated thus, from time to time the basement floors of some houses are flooded.
Major Environmental problems in Istanbul
Istanbul is the 24th largest city in the world with a total population over 10 million, (World Urbanisation Prospects, 1994). In USA, 100 cities have been selected to evaluate them according to various urbanisation factors. Sydney and Seattle shared the winning prize with 86 points, where Istanbul was at the 65th city with 37 points. However, the capital of Turkey, which is at the same time, the second largest city of the country was at the 43rd place. Istanbul faces various environmental problems due to rapid population increase, illegal housing and industrialisation. In years when migration from the other parts of the country started, the investigation of its infrastructure pointed out that, drinking water supply to the city was quite insufficient and that only a minority of the city (20%) utilised safe drinking water. From then onwards, the population continued to increase significantly each year, however, land availability to migrating population could not be satisfied with ease. Each year, the megacity widened in population of somewhat like a city of Eskisehir or Samsun. The city plans could not be completed in time, and infrastructure planning and application facilities were not maintained in parallel to this population increase. Even the existing residential areas could not receive sufficient infrastructure services. The condition of Istanbul in terms of drinking water supply can be investigated by considering three main regions of urbanisation;
- The historical part of the city, the old town between Besiktas – Kadikoy -Golden Horn- receiving sufficient drinking water,
- The surrounding area of the old town established between years 1950 – 1960, such as Gaziosmanpasa, Umraniye, Bagcilar receiving drinking water intermittently,
- New settlement areas such as Sultanbeyli, Esenyurt, Altinsehir where drinking water is supplied through transportation vehicles.
The water supply to the city was maximum 500,000 m3/year within the arid years of 1993-1994. Nowadays, this supply value increased up to 1 billion m3 / year during rainy seasons. Istanbul supplies 95% its drinking water demands from surface water through constructed reservoirs. Table 1 shows the present status of water supply reservoirs of the city.
Table 1. Currently Available Water Resources of Istanbul (Eroglu & Sarikaya, 1998)
Considering the water losses and industrial needs, the actual domestic water requirement is around 50-100 Lt/cap. /day rather than the calculated value of 250 Lt/cap. /day. However, the existing quality of the reservoirs should be considered. They highly need treatment prior to consumption. The water treatment processes applied for surface water treatment are pre- oxidation (chlorinating or ozonation), coagulation, flocculation, sedimentation, filtration and post disinfection.
Wastewater collection, treatment and discharge duties have accelerated during 1980’s. The prepared projects started to be applied. The first of these projects was the “Southern Golden Horn Collector, Yenikapi Pre-treatment Plant and Ahirkapi Sea Discharge Project”. The wastewater are collected, pre-treated and discharged to sea. It is the first marine discharge application. The collected wastewater passed through a preliminary treatment plant consisting of screens and grit chamber and the marine discharge system consisted of piping of 1100 m. length and depth 60 m given from Ahirkapi where two layers flow was detected. The system was completed in 1988. The following projects were similar to the one of Prof. Kehr, prepared in the years 1959-1966, and Damoc Projects prepared between 1966-1970 constituting the basis of the present day applications where the main opinion was the application of preliminary treatment followed by marine discharge system as the best available technology to be applied to the Sea of Marmara. In future it is determined to apply biological treatment to these systems especially in regions where the currents are less significant and where the sea depth is limited.
Within the past years, the preliminary treatment and marine disposal systems of Uskudar, Baltalimani, Adalar have been completed. The biological treatment plants of Tuzla and Buyuk Cekmece have started operation. Thus, within the previous 10 years, the treated wastewater percentage increased from 3% to 60%. The target is to reach a value of 95% by the end of year 2000. Figure 1 shows the present situation of wastewater management studies in Greater Metropolis Istanbul.
PROBABLE EFFECTS OF EARTHQUAKES ON INFRASTRUCTURE
The continuously occurring earthquakes in the neighbourhood provinces and districts of Istanbul for almost more than three months increased the probability of earthquakes to be felt seriously in Istanbul in the near future. Thus, every citizen must share the experience of the Kocaeli and Duzce earthquakes and necessary precautions must be taken to prevent significant damages. One of the most important probable effect of earthquakes in a megacity like Istanbul is the damage of infrastructure features such as water transmission lines, sewer lines, water treatment plants, wastewater treatment plants, sea outfall systems, electricity transmission lines, communication lines, highways, roads and natural gas pipelines. In the major earthquake of August 17, 1999 at Kocaeli put forth these realities. For example, the water supply systems of Adapazari were highly damaged, (Eroglu, 1999). The authorities were not very active in solving these problems with the effect of significant damages, deaths and injure. They were also not well equipped technically. Lack of proper organisation and co-ordination between various rescue groups continued for a few days. In particular, support and assistance from the central government, city governors and from all the related official and private associations were needed. Previous struggles experienced in the past earthquakes of Dinar (1995), Adana- Ceyhan (1998) were utilised in the struggles of this Kocaeli earthquake, 7.4 on the Richter scale. Istanbul also felt this earthquake and parts of the megacity were damaged.
As it was summer season and as very sensitive instruments were installed at the highly sensitive lines, no damage was inspected at natural gas pipelines. In particular, IGDAS (Istanbul Gas Distribution Company) must also take the necessary precautions for the winter season. We have learned the death of many people because of fires at the previous Kobe earthquake.
Generally electricity cuts are experienced just after the occurrence of earthquakes. In a megacity like Istanbul these sudden cuts lead the sewage and drinking water supply systems to be out of operation. One of the important needs of such cities is generators of various capacities to continue the required distribution. Even though the centre of Kocaeli was kilometres away from Istanbul, the infrastructure services were cut just after the earthquake and the services of electricity, water supply and natural gas were again in service at 14.30 of that day. This was almost a delay of services for 12 hours. The water pipes of the damaged buildings were immediately cut to prevent water filling in wreckage. After the occurrence of earthquakes, the vital things needed at the region are drinking water transferred in tankers, disinfectants like chlorine, chlorinating equipment, mobile generators, mobile toilets solid waste collectors like garbage bags concerning infrastructure services. In general, chlorine consumption increases under such circumstances. This fact was also observed in Kocaeli earthquake, however, no problem had been arisen in terms of chlorine supply as the production of it continued without any breakdown at Izmir Petkim Aliaga Plants. Thus, in future planning the urgent need of chlorine must be considered.
As in the experience of Kocaeli earthquake, Water Works and Sewerage Administration of Greater Istanbul (ISKI) was involved in repairing the lines and pipes at the earthquake region as well as supporting them with trained personnel and equipment. Water distribution started again in Kocaeli, Darica, and Cayirova regions at 14.30 of that day. There was a significant drinking water deficit in the area, and ISKI overtook the responsibility and sent water from Bostanci Water Filling Station to Yalova and Golcuk through sea tankers, (Eroglu, 1999). The other needs were lime to be used for preventing the activity of infectious diseases, mobile and/or ready toilets, pipes, pipe fittings, etc, for mobile water treatment units or repairing the water transmission lines and sewage collection systems. ISKI searched for any damages in the existing water supply systems at the region, Gokcedere dam, Yalova Water Treatment Plant, Altinova Pumping Station and the other water storage tanks and water transmission lines. All the systems were almost firm and strong except 11 refraction along the lines. The transmission troubles were overcome and water was again supplied to the consumers in a shorter period of time. In Adapazari province, drinking water is supplied from Lake Sapanca. The water transfer pumps at the entrance to the city were transmitted to water treatment plants and than directly to the consumers. The two piping lines between the lake and the treatment plant of diameter 700 mm and 1200 mm were both out of operation after the earthquake. These transmission lines were immediately repaired and put on service again. The two-undamaged districts of the city and the State hospital were supplied with water. Also, 7 water filling stations were installed to receive water transported through tankers. ISKI stopped all the tankers on their way to these filling stations and chlorinated them. Water distribution was permitted after chlorinating. The region between Yalova and Golcuk, a distance of approximately 60 kilometres was highly effected during the Kocaeli earthquake. Almost 60% of the inhabitants migrated to other parts of the country or moved to live in tents as their houses were highly damaged. No water through the water supply systems was distributed due to defects at various points on the water transmission lines, which are made of steel of various diameters, 400 – 1000 mm. till August 27,1999. Three days later at August 30, 1999 water is started to be given to almost 60% of the water transmission system and the next day, at 31 August this percentile increased up to 75%. In particular, it has been observed that 25% – 30% of the infrastructure was suffering from damage at the area. That was the main reason of not supplying water to the consumers in a shorter period of time.
Water is surely a vital element, but it is also necessary for washing dishes and clothes, and for bathing. Human health can be kept at good condition unless clean water is supplied for various needs of inhabitants. Therefore, in cities like Istanbul, keeping in mind its geologic transformations and high probability of facing earthquakes, urgent precautions should be taken towards prevailing the existing and future projected infrastructure against probable damage.
The priorities of urbanisation in most of the developing countries are prevention of migration, prevention of population increase, thus instead of megacities forming highly urbanised all around the countries. Thus, like in developed countries, the population increase in the cities will remain within acceptable values. Therefore, the local authorities will be able to perform proper infrastructure services. The residential areas will maintain satisfactory standard of living for the inhabitants. If satisfactory and proper infrastructure services are supplied like water supply, wastewater treatment and disposal, the surface water supplies will no longer be polluted and they will be converted to places where people will like to walk around and swim and utilise them for recreational purposes. Also the missing species will start to appear again and ecological balance will again be achieved. Thus, in developing countries, the cities suffering from high population, illegal housing and rapid urbanisation may become healthy environments if certain mentioned precautions are considered. This fact is of utmost importance in considering the probable effects of earthquakes on the existing infrastructure. As Istanbul is located at a very strategic geological structure, special care must be considered in keeping all the infrastructure features in satisfactory condition. This will be accomplished by proper re-planning, management, training and financing based on technical knowledge and extensive experience gained after the Kocaeli and Duzce earthquakes. Another point that is quite important to be considered is that just after the occurrence of earthquakes emphasis is given to superstructure, however, it is of utmost importance to consider infrastructure as well at the same time for the sake, safeties and healthiness of the inhabitants.
- Eroglu, V. And Sarikaya, H.Z. (1998). Achievements Towards Better Water Supply and Wastewater Disposal in Istanbul, International Symposium on Water Supply and Treatment, Proceedings, Istanbul Water and Sewerage Administration, ITU and Water Trusty, 25-26 May 1998, pp. 1-19.
- Eroglu, V. (1999). Precautions to be taken during and After Earthquakes, ISKI, Istanbul Water and Sewerage Administration, Istanbul.
- ISKI. (1998). Istanbul Water and Sewerage Administration, Annual Report, Istanbul Metropolitan Municipality.
- Linares, C.A., Seligman, D.A., Tunstall, D.B. (1993). Developing Urban Environmental Indicators in Third World Cities, Report presented to US Agency for International Development, World Resources Institute, Washington, D. C., and p.5.
- World Resources. (1996-1997). A Guide to the Global Environment, The Urban Environment, An Official Publication of Habitat II, The United Nations Conference on Human Settlements, June 1996.
- World Urbanisation Prospects. (1994). United Nations Population Division, 1994 Revision, pp.143-150.