Water
Nature has its own way of maintaining equilibrium. It is the same with water. Water in the atmosphere falls, or precipitates, from the clouds in the form of rain, and it becomes surface runoff and flow into oceans. At last, the water will evaporate into the atmosphere and this process repeats, thus forming the water cycle.
When developing a new city, the soil is slowly covered by asphalt, cement, and other surface structures for road construction. There is less and less ground that water can infiltrate through and reach the soil. Therefore, cities need to build a drainage system that guides water into the river. This means the city has unwittingly changed the naturally occurring water cycle in the environment. As a result, we need to alter our approach to water management.
In general, there are two primary concerns when it comes to water management, the external water and the internal water:
First, external water is defined by water that is blocked by an embankment from entering the city’s drainage system. It is crucial to regulate external water in order to prevent flooding; this can be done by managing bypasses or building and reinforcing embankments. For example, the embankment along the Tamsui River in Taipei was built to last for 200 years. Therefore, under proper management and maintenance of the embankment, external water should not flood the city.
Second, internal water - water within the city limits - needs to be discharged into the river using the city’s drainage system. During times of typhoons or heavy rainfall, the level of external water in rivers may rise up, and floodgates would be closed at this time to prevent external water from gushing into the city. Then, pumping stations would pump the internal water out of the city. In certain cases when the level of rainfall exceeds the pumping station’s capacity, internal water cannot be discharged quickly enough, resulting in floods in the city.
Therefore, the strategy for water management in recent years is to build a “permeable city” that allows internal water to infiltrate into the soil and return to the natural water cycle. The first step in achieving this goal is the revolutionary invention of permeable pavements.
Reference：
1. Chen, Shen-Hsien. (December, 2014).
New strategy for urban water management—permeable/sponge city
2. Shen Hsien-Chen Interview
By Gordan Huang