Flooding is a common phenomenon in Java’s northern coastal regions. Climate change is to blame to some extent; the floods are due to climate changes such as rising sea levels. However in Jakarta, there is the additional problem of large quantities of groundwater being extracted from the ground and is then used as drinking water. Nature is trying to refill the amount that is extracted although this proces takes a lot of time. However the amount that is being extracted is far higher. As a result, this lowers the soil level, causing the city to sink and increase the flooding.
Drainage systems of Jakarta were built by the Dutch almost a 100 years ago during the Dutch occupation of Indonesia. This system has become outdated and neglected. The drainage system is clogged with waste. which is the cause of its failure.
Three factors are to blame the flooding of Jakarta: firstly, from the sea. As sea levels start to rise, due to global warming, more water is forced to enter the city.’Secondly, water coming from the mainlands of Indonesia that pass through Jakarta’s drainage system. ‘Thirdly, heavy rainfall pushes Jakarta’s capacity to the max to distribute the water. ‘These factors results into huge parts of the city being overwhelmed by the amount of water. The flood leaves its marks in the infrastructure and countless homes, leaving countless families homeless. Also, health problems start to arise due to extremely unhygienic conditions. This is the result of old and congested ‘open’ drainage systems. The drainage system of Jakarta is built on the surface and covered with slabs of concrete. When these drains start to overflow due to congestion, all the build up starts to come out on the streets and enter houses. This however, is a common problem in poor areas of the city. In short, poor areas are prone to floods and experience more problems in comparison with the more rich areas.
Witteveen+Bos organised in Jakarta in 2001 a seminar about reducing water problems. The seminar attracted a lot of interest of representatives of the Indonesian government who attended the seminar. Thus initiating the idea of building a polder. ‘A polder is a low-lying area, in which the water is being controlled artificially and contained by dikes. Also, a water board has been established to consult and oversee the water projects. The board consists of eight people, three local residents, three professors, and two people representing the authorities.”A number of matters must be organised before a polder can be created: besides the technical preparation, there is the institutional aspect. The Netherlands has water boards and district water boards that take care of water management. Indonesia does not have anything similar on a comparable scale. So a water board was established to manage the pilot polder. It is being overseen by the Dutch district water board of Schieland and Krimpenerwaard. The new water board consists of eight people, including three local residents, three professors, and two people representing the authorities. There was a groundbreaking ceremony in April 2010 at which the Mayor of Semarang, the Governor of the Central Java province, and the Secretary General of the Ministry of Public Works signed treaties for transferring powers to the water board ‘ some of which are far-reaching by Indonesian standards. The water board will devise, write, and introduce all rules, procedures, and protocols necessary to ensure the proper working of the polder.
Creation of the polder is now on the eve of the call for tenders. The necessary activities include:
‘ constructing dikes
‘ building pumping stations
‘ dredging rivers to create more drainage capacity
‘ revitalising the drainage system in the city
‘ controlling waste
‘ constructing retention basins
These activities were prepared by Witteveen+Bos in cooperation with the Indonesian parties, from the plan phase and feasibility study all the way through to the design and specifications. We will also oversee the construction work.
Managing the polder will cost money, some of which will have to be provided by local residents. But they will want to see results before they part with any money. Support must be mustered for paying and a payment structure (‘water rates’) must be set up. Once everything is working, the population will be better off financially on balance, because there will be less damage to homes and infrastructure, land prices will go up, the area will be more attractive economically, and there will be less loss of income through damage and illness. However, there must be starting capital first. This is being raised by various parties, partly through donations and subsidies. Witteveen+Bos has also contributed to this effort.
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