Flooding is commonplace in Java's northern coastal regions. To some extent, the floods are due to climate changes like increased precipitation and rising sea levels. But in the urban areas, there is the additional problem of large quantities of groundwater being extracted from the soil for use as drinking water. This lowers the soil level and increases flooding. The result is immediately visible: there is water in the streets much of the day as the tide pushes the groundwater up to the surface. Some houses are now permanently under water.
Floods threaten urban coastal regions in two ways: from the sea and from the hinterland through the drainage of rainwater via rivers and canals. Major floods damage houses and infrastructure, but also cause unhygienic conditions. This is because most of the towns have open sewers, so when floods occur, the contents of the sewers flow into the town. The poorest urban districts generally experience most inconvenience, as poor people are unable to take the required measures or to move house.
The only short-term solution to this water problem appears to be the construction of a polder. A polder is a low-lying area, surrounded by dikes, in which the water level is controlled artificially. Most people are unable to move to higher areas, so the problem has to be tackled locally. At the same time, soil subsidence will continue unabated until implementation of an alternative to extracting groundwater. For the time being, the only answer is to control the water level.