According to the statistics carried out and assessed by National Emergency Management on July 20, overall damage from the flood by watershed in regions near the Four Rivers Restoration Project was estimated to be approximately 104 billion KRW (97 million USD as of September 9, 2011). This amount comprised casualties, public and private territorial damage, and other damages all together. Compared to last year’s figure with a typhoon Kompasu, the Four Rivers Restoration Project’s initiative year, as 195billion KRW (182million USD as of September 9, 2011), this year’s figure was about the half. Especially with a typhoon Rusa in 2002, a typhoon MaeMi in 2003, and a typhoon Ewiniar in 2006, this figure is less than one-tenth of the previous damage.
3.5-Folds Rainfalls Increased 3.5-Folds
A research of the National Weather Service reported that Korea’s monsoon season was extended a week longer than the previous year and heavy rain was more frequent. Precipitation rate of more than 30mm an hour was observed across the country 65 times to be 3.5 times that of last year. 10 days of straight rain was record-breaking as the most prolonged raining period.
50% Down Came the Half of Annual Rainfall in Just One Month
Nation’s average precipitation rate for a month from June 22 to July 16 was 642mm 2.5 times of last year. Having an annual average precipitation rate as 1245mm, this year Korea had more than half of the usual rate solely within a month. Combined results from the National Weather Service and National Emergency Management conclude that this year’s June to July precipitation rate has reached nearly 50 percent of the annual rate.
217ha Flood-free Fields and Paddies by Farmland Remodeling
Last July, 217ha of ShinChon District in ChangWon city, KyungNam province was submerged due to 137mm of torrential rainfalls. This June, however, agricultural land was not inundated even with 136mm of the precipitation rate, thanks to elevated land level with the dredged soil. 24ha of Jeungsan District in Buyeo was also submerged in July, 2005. Precipitation rate that year was 129mm. This year between June 22 and 25, the precipitation rate was 253mm which was twice of that in 2005, however, the area was safe. Remodeling effect was indisputably proven. Areas of Oksung-myeon in Gumi city, of Sangju weir in Sangju city, and agricultural land of ChangYeong province and HapCheon province used to be all very prone to floods, but the risk to be submerged in the future is close to zero. For the agricultural land has been raised with dredged soil from bottom of the river, permanent flood control is promising. Korea Rural Community and Corporation and farmers of the area are looking forward to completion of the project.
Artificial Island Construction Site in Old River Channels of YoungSan River, Zone 2 Various aquatic plants are being set out.
3.78m Riverside Flood Stage Lowered by 3.78 Thanks to Dredging Effect
Even with a greater amount of rainfalls than that of last year, flooding near drainage areas was not observed. There was not a single case of immerged areas, damages and collapses from refluxed river situation. Especially in HamAhn district of KyungNam, ChangYeong district, Goryeong district and HapCheon district that were very much prone to floods, dreadful news of inundation were not heard. Experts analyze that it is because the total flood stage has been lowered as much as the bottom of the river lowered by dredging of the Four Rivers Project. According to the Office of National River Restoration, flood stage of NakDong, SangJu areas was lowered by 3.78, Han River (Yeo-Ju) by 2.54m, Geum River (YunGi) by 3.36m, and YeongSan River (NaJu) by 2.13m respectively.
0.5m Lowered Water level of the Main Stream Reduced that of the Tributaries
Anti-Four Rivers Restoration Project group has been objecting to Four Rivers Project with an assertion that tributary river streams require restoration before the main stream as there is more flood damage in tributary area. However, it was proven that dredging main stream before the tributary was the right idea. Lowered water level of the main stream automatically brought down water level of the tributaries. It was estimated that water level was decreased; respectively Sum River (tributary of Han River) by approximately 0.5m, Hwang River (tributary of NakDong River) by approximately 1.3m, MiHo Stream (tributary of Geum River) by approximately 0.5m, and HwangRyeong River (tributary of YeongSan River) by approximately 0.6m. The government’s prediction was proven correct as water lever of the tributaries has been decreased.
