Groundwater Level Reduction Caused by the Karst Collapse Geological Hazard in Yiyang, Hunan Province

After more than one week of investigation, the cause of the karst collapse in 693 karst collapses in Yuejiaqiao Town, Yiyang City, Hunan Province from January to February 24 was investigated. The Geological Environment Department of the Ministry of Land and Resources of Hunan Province announced the results of the survey recently. Local karst hydrological and geological conditions are important causes of disasters, and the significant reduction in water levels caused by human activities involving drainage of groundwater is the direct cause of induced disasters.

“According to the survey, the dry wells in the town of Yuejiaqiao and the collapsed pits that caused the tributaries of the tributaries of the river were not able to see the groundwater level, indicating that the groundwater level in the area has been significantly reduced, and groundwater in a range of 7.5 square kilometers has been caused. Significantly lower, even lower than the low-emission reference plane in the region, only the effects of drought and no human engineering activities are difficult to form.”

An investigator told the reporter that there are underground water wells, a number of cement limestone mines, and more than a dozen coal mines within 10 kilometers of the town and its surroundings. Although the survey conducted by the investigation team on the dynamics of drainage in some mines shows no corresponding relationship with ground subsidence, it is an objective existence that the groundwater level in the area is significantly reduced by artificially pumping groundwater, and it is also a direct cause of disasters.

The survey report also shows that the occurrence of ground subsidence is clearly and positively related to the recent continuous rainfall. From September to November 2011, the area in the town of Yuejiaqiao suffered from prolonged drought. Since December, the area has continued to rain, and the collapse deformation has gradually increased. Especially in early February of this year, local rainfall increased and ground collapse reached a peak. “Long-term droughts have exacerbated the reduction of groundwater levels, and with the sudden infiltration of large amounts of rainwater into the ground, the potential for latent corrosion has increased and the soil particles in contact with the cavernous gaps have gradually been brought into the caverns, causing ground subsidence and deformation,” the investigators explained. .

The Hunan Provincial Department of Land and Resources issued a warning that the hydrogeological conditions for the formation of karst collapse have not changed at present, and the human activities and sustained rainfall factors that induce ground subsidence still exist and are intensifying, and the groundwater level has not been restored. With the current growth and intensity of rainfall in Hunan, the role of subsurface erosion will continue to increase, and ground subsidence will continue to occur.

According to the reporter’s understanding, as of the beginning of March, the geological disaster occurred in 9 villages in the affected area of ​​the town, causing a total of 193 houses to crack and sink. There are 572 farmland collapses and 17,000 mu farmland cannot be cultivated normally. 150 rivers collapsed and 35 other dams such as reservoirs, ponds, dams and channels were destroyed. In addition, 7 power facilities and 2 communication facilities were damaged, and 42 village roads were damaged. The total number of people affected by the disaster totaled 5,670 households with 18,000 people, but there were no casualties.

The deputy mayor of Yuejiaqiao Town, Zhong Meiliang, told reporters that 10 houses that had been damaged were seriously relocated. The vast majority of evacuees have solved temporary housing problems by renting their own homes and investing in friends and relatives. The town has issued an emergency subsidy of 300 yuan per person to the evacuees. While Yiyang City is currently actively repairing various types of facilities, it is also stepping up the deployment of preventive measures to deal with possible new rounds of disasters.

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