The Yeoju Retention Area played a meaningful role in preventing the Han River from being flooded. The retention site (Daesin-myeon, Yeoju-gun, Gyeonggi-do) is a huge water tank transformed from an ex-farmland area after being dug up to 7 meter depth. It was designed to accommodate a 30-year precipitation. So, when it arises more than 36.37 meters above sea level, inundated water is to flow inside the retention area. This huge retention area’s scale is as large as 259 football fields (1.85 million m²), and can hold 15.3 million tons of water. Jangma (Korean rainy season) of this year proved the reason why the existence for this retention site. An example would be the fact that it blocked the inundation of the Goksu Stream, a tributary of the Namhan River.
That stream has 80 meter width with 7 to 8 meter high banks alongside it. Therefore, it had been flooded almost every summer rainy season to make environs agricultural area waterlogged. With only 100 mm rainfall easily made this area sunken because it is low level, hard to be drained and even with frequent counterflow of the Goksu Stream. But, this year showed difference. Thanks to the newly created retention area between Namhan River and Goksu Stream, the water from the Goksu Stream and rice paddies of Namdang-ri could be drained directly to the retention area and the village could be safe from inundation. In the Yeoju area, there was average 153.2 mm rainfall for just one day, and some spots had record of 199.5 mm. In Chungju area, the upstream, it rained 876 mm. That was a triple than usual amount of other years and 2.5 times larger than even the recent top record of year 2006. However, as the water level came to be stabilized, there was no flood damage in the Namhan River area. Level of river has retained less than 30 meter near the Ipo Weir. It is also far from the limiting line of flood level of the Ipo Weir (36.24 m).
