The differences which have occurred in the amount and severity of precipitation based on the global climate change have caused an increase in high water disasters caused by floods which have been observed frequently in recent years. The protective layer on the slopes of the upright basins of the streams are destroyed within time and such lands are intended to be converted into agricultural lands; as a result of the increasing erosion, the natural stream beds are filled with sediments and high water occurs unavoidably. The massive settlement along streams increases the severity of the floods to occur. The prevention of slope erosion and of any sedimentation movements in the stream beds is realized by stream improvement and flood protection projects.
The global climate change, together with the increasing population and decreasing natural resources has brought out the idea of recycling wastewaters. Wastewater collection and treatment plants have been projected in order to recover wastewaters. There is a trend to construct domestic wastewater facilities at the potable water dam lake and stream basins. The treated waters have been initiated to be used for agricultural irrigation and have been lifted to quality for domestic use.