[Letters] Reducing the risk of urban floodsIt’s been over a year since Seoul suffered the urban flood that resulted in the collapse of Umyeon Mountain, paralysis in the subway system and water damage on modern structures. The city of Seoul and the National Emergency Management Agency are busy preparing and implementing flood control plans, including a large rainwater retaining facility.
If you look at the causes of the flood, you can tell that the climate change is more responsible than the physical capacity of flood control facilities around the city. In 2011, Seoul had 2,039 mm (80 inches) of rain, 590 mm more than the average of the past 30 years. Moreover, 30 to 50 percent of the surface areas in a metropolitan city are impermeable layers. Therefore, the rainfall flows down the surface rather than permeating into the ground, causing a flood in the lower areas. The inundation of Gwanghwamun, paralysis of the metro system and the flooded Gangnam area prove that we need more fundamental solutions.
Flood control is one of the most important national tasks, next to national defense. Therefore, the central government and legislatures need to act more aggressively and seek fundamental solutions to help local cities implement systematic water control programs through technical, administrative and legal supports.
The most urgent task is to make a law on urban flood prevention to control the rainfall runoff. Rainfall runoff penalties should be imposed on violation. The water control law should be made as a higher law than the existing building and construction-related laws. The decentralized rainwater control and the low impact development (LID) technology used in Germany as flood prevention should be adapted and widely implemented. When a daily rainfall of 40 mm is processed using the decentralized control of permeation, collection and evapotranspiration, the drain pipe load and the risk of urban flood can be reduced by one third.
* Heo Woo-young, director of the LID Solution /Rainwater Life Science Convergence and Integration Institute.
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