The Haihe River Basin Faces Heavy Rains and Flooding: The Importance of Flood Storage and Detention Areas
Recently, the Haihe River Basin in China has been heavily impacted by severe weather conditions, including torrential rains and flooding caused by typhoon “Du Su Rui” and other unfavorable factors. As a result, many areas have been affected, leading to the issuance of red warnings for heavy rain in the Beijing-Tianjin-Hebei region and the closure of scenic spots. However, some individuals have questioned these measures, labeling them as “overkill” and expressing confusion about the opening of flood storage and detention areas. To clarify these actions, it is important to understand that they are scientific risk-avoidance measures implemented after careful research and judgment by experts from meteorological and water conservancy departments.
The heavy rainfall in the Haihe River Basin during this period has necessitated the use of flood storage and detention areas. From July 28 to August 1, the basin experienced an average rainfall of 129 millimeters, with the total precipitation exceeding 40 billion cubic meters. To put this into perspective, the Three Gorges Reservoir in the Yangtze River Basin, which is China’s largest reservoir, has a total storage capacity of 39.3 billion cubic meters. The recent precipitation surpassed even the flood control storage capacity of the Three Gorges Reservoir, emphasizing the severity of the situation.
Although the average annual precipitation in the Haihe River Basin is typically lower than that of the Yangtze River Basin, extreme weather conditions like this cannot be fully mitigated by existing water conservancy measures. This round of rainfall has even broken 140 years of instrumental measurement records in the Beijing area. In response to the flooding, the water conservancy department has taken measures to adjust reservoir operations, effectively reducing downstream flood pressure. All 155 large and medium-sized reservoirs in the Haihe River Basin are currently engaged in flood control efforts.
Reservoirs and flood storage and detention areas play a crucial role in the flood control system. These flood storage areas are temporary zones for storing excess water during floods, typically situated in low-lying areas and lakes outside river embankments that have been historically prone to submersion. When flood levels become too high, the utilization of these areas helps to minimize disaster risks by storing excess water and reducing flood peaks. This scientifically proven method has been implemented in flood control practices worldwide.
China has established a total of 98 national flood storage and detention areas, including 28 in the Haihe River Basin, as stipulated in the Revised List of National Flood Storage and Detention Areas (2010). In response to the recent heavy rain and flooding, eight flood storage and detention areas have been opened in the Haihe River Basin. As of August 3, over 1.2 million people in Hebei Province have been relocated, with more than 850,000 people evacuated from flood storage and detention areas. Analysis of historical data from 1950 to 2021 indicates that 66 out of the 98 national flood storage and detention areas have been utilized, with a cumulative flood storage capacity exceeding 140 billion cubic meters.
It is important to note that the risk of geological disasters persists even after rainfall subsides. Mountainous areas may still experience rockfalls, landslides, and ground subsidence due to soil saturation. The western and northern regions of Beijing, as well as western Hebei, which have experienced substantial rainfall, remain at risk of such geological hazards. As a precautionary measure, the public is advised to avoid entering mountainous areas and steer clear of potentially dangerous sites over the next two to three weeks.
Additionally, the risk of flooding in low-lying areas remains high as water flows from the mountains into the plains. Historical records from August 1963 demonstrate that water levels in downstream rivers and accumulated water in plain depressions can persist for several days or even weeks after heavy rain has ceased. Thus, the use of flood storage and detention areas remains crucial in mitigating flood hazards. Adequate precautions and evacuation efforts are necessary to ensure public safety.
Long-term development in China’s disaster prevention systems and infrastructure can further enhance resilience. The construction of wetland parks that double as flood storage and detention areas and the prohibition of building houses in dry riverbeds are essential considerations. Furthermore, post-disaster reconstruction efforts should prioritize the timely restoration of normalcy in affected areas. The merciless nature of floods underscores the imperative for scientific strategies and collective efforts in disaster prevention and mitigation.
(Source: Economic Daily)