CCTV News (Reporter/Kan Chunyu Yao Shuting): Affected by Typhoon "Du Surui", the recent heavy rainfall in North China has been fierce, wide and intense, and some rivers have experienced varying degrees of water rise. The Beijing-Tianjin-Hebei region has used flood storage and detention areas to orderly divide river floods. Up to now, Hebei Province has successively opened 7 flood storage and detention areas, and completed the transfer of 84,74 people.
Flood storage and detention areas are an important part of China's river basin flood prevention and disaster reduction system, which has played an irreplaceable role in the defense of major floods in the river basin, and basically guaranteed the safety of important cities and important flood control areas in the middle and lower reaches of rivers. According to statistics, from 1950 to 2021, 98 of the 66 national flood storage and detention areas were opened a total of 424 times, with a cumulative flood storage and detention capacity of more than 1400 billion cubic meters. The flood storage and detention areas that were successively used in Hebei were also used during the floods in the Haihe River Basin in 1963 and 1996.
Cheng Xiaotao, deputy chief engineer of China Institute of Water Resources and Hydropower Research, said that flood storage and detention areas are an important part of the flood control system, which are low-lying areas and lakes that temporarily store floods outside river embankments, most of which are places where rivers flooded in history. When floods are too large, timely storage of floodwaters and reduction of flood peaks can minimize disaster losses.
News+: What is a flood storage area?
Cheng Xiaotao: Flood storage and detention areas are an important part of the flood control system. Floodwaters can be temporarily stored in low-lying areas on both sides of rivers, or in wetlands and lakes.
The banks of the river are not all highlands, and there are also low-lying areas that used to be prone to flooding whenever the water rose. As populations grow and dikes are built along rivers, these lower-lying areas are less likely to be flooded. Gradually, some low-lying land was reclaimed into farmland, inhabited, and gradually formed villages.
In the event of a mega-flood, to reduce the pressure on downstream cities, it is necessary to reduce the peak flow of the river. As a result, some sub-flood storage areas are set up, and when the flood peak passes through the flood storage area, the flood water is diverted into the area outside these levees by opening the gates or peeling off the embankments.
Historically, these flood diversion processes may have been natural, and these areas were flooded during previous major floods, but now they are flood storage and detention areas.
However, the existing dikes and pumping stations effectively reduce the probability of flooding in these areas. An additional embankment is usually built to prevent water flowing into the reservoir area from spreading everywhere after flooding. Floodwaters are stored in the reservoir area, and when the river peak has passed and the water level has decreased, the water in the reservoir area is discharged back into the channel.
News+: Why are flood storage and detention areas designated?
Cheng Xiaotao: Different rivers have different sections of size, depth and depth, so the ability of rivers to carry floods is also different. When the amount of floodwater exceeds the capacity of the river, the river is likely to flood.
In order to improve the flood carrying capacity of the river, we built embankments along the river, which is equivalent to expanding the section of the flood flow. But the levees are so long that we can't guarantee flooding in every place. In order to avoid flooding, we have to carry out a full line of defense and set up flood storage and detention areas, so that we can clearly divide the flood areas and reduce the flood control pressure of key protected areas. Such planned flooded areas are called flood storage and detention areas, which is essentially a measure to relieve flood control pressure along the entire river channel and divide flood protection priorities.
Floodwater flowing into the reservoir area returns to the same path after the water level in the main channel drops, a process called "receding". Some flood storage and detention areas have a flood gate upstream and a receding gate downstream, which can retreat the water, and the flood in these areas is a temporary stay.
"News+" reporter: How do you view the statement that "Hebei and Tianjin flood discharge is to protect Beijing"?
Cheng Xiaotao: I don't think it's a very accurate statement. The application of flood storage and detention area is considered at the scale of the river basin, generally speaking, the effectiveness of flood storage and detention area is for the downstream, not for the upstream, so the application of the flood storage and detention area is for Tianjin. The lowering of the water level in Tianjin does not mean that Beijing will not be flooded.
News+: After the flood release, how to restore the living order of residents in flood storage and detention areas?
Cheng Xiaotao: Flood storage and detention areas are not only an important part of the flood control system, but also the home for the survival of ordinary people in flood storage and detention areas. The ordinary people in the flood storage areas are also citizens of the People's Republic of China, and they also have the right to development, not that they should be sacrificed.
Therefore, when the Flood Prevention Law of the People's Republic of China was enacted in 1997, it was clear that the state would compensate if it used flood storage and detention areas. The Interim Measures for Compensation for the Use of Flood Storage and Detention Areas, promulgated in 2000, also provides a detailed explanation of the compensation standards.