[The Hwankyung Ilbo] The Ministry of Environment (Minister Han Jung-ae) announced a plan to follow up on the causes of flood at Sejong Government Complex on August 3 for a total of 158 districts, including 78 downstream dam of Seomjingang Dam, 53 downstream of Yongdam Dam, Daecheong Dam, and 27 downstream Namgang Dam.

First, the Korea Water Resources Association (Chairman Bae Deok-hyo) announced the results of its investigation into the causes of flood (December 2020-July 2021).

Last year, the causes of flooding downstream of the dam were mixed with torrential rain, insufficient management of dam operation and related systems, insufficient flood management linked to dams and streams, and lack of preventive investment and maintenance.

Subsequently, Hong Jeong-ki, Vice Minister of Environment, announced the government's follow-up plan. 

Vice Minister Hong also stated: "The government plans to actively support and cooperate in order to expedite the damage relief process under the Environmental Dispute Mediation Act revised in April last year. We will implement the comprehensive measures for wind and flood response jointly established in November last year and prepare port measures and detailed implementation plans."

Poor system maintenance reflected in abnormal weather conditions: 

Heavy rains caused damage in a total of 158 areas last year, including 78 districts downstream of the Seomjingang Dam, 53 districts downstream of Yongdam Dam and Daecheong Dam, and 27 districts downstream of Hapcheon Dam and Namgang Dam.

Looking at the common problems of downstream areas of the three dams from a legal and institutional perspective, efforts have been insufficient to reflect changes in conditions due to abnormal weather, such as maintaining planned discharge volume at the time of completion of the dam.

In particular, the Seomjingang Dam has a flood control capacity of about 40% of the nation's average (17.2%), compared to the total reservoir, and special measures are expected to be taken to secure flood control capacity in the future.

It has also been confirmed that the flood defense plan has remained at the frequency of 100-200 years for national rivers and 50-100 years for local rivers, failing to reflect the increase in precipitation due to climate change.

Flood response in the basin is important for continuity and connection of upstream and downstream rivers, but there are differences in flood defense goals between dams and streams, and there are limitations in efficient operation of dams to reduce flood damage during torrential rains.

The results of evaluation in terms of operation and management of dams also showed insufficient results. 

According to last year's operation level of the dam, it maintained a higher level in the early flood season (June 21) than in previous years, and some dams were not actively responding to the continuous flood wave, such as exceeding the flood limit.

In addition, the dam manager notified the relevant agencies of the dam discharge information within the criteria given in the regulations, but it was partially confirmed that there was a lack of response time due to the delay of the regulations.

In terms of river management, the river maintenance was delayed due to the basic plan of the river due to financial, social, technical constraints, or insufficient river maintenance.

In addition, damage occurred due to the lack of river mooring and levees, the loss of levees around the structure, and the overflow of vulnerable facilities such as bridges and roads installed under the planned flood.

In addition, the installation and maintenance of facilities such as drainage pump stations and drainage doors caused flooding damage due to poor backflow and poor domestic exclusion to low-lying areas such as agricultural land. 

Lack of dam operational skills:  

Looking at the situation downstream of the dam, Yongdam Dam had difficulty in controlling the flood as it exceeded the flood season limit since July 30 due to the prospect of the end of the rainy season and complaints from downstream areas.

As a result, the flood management failed to actively respond to flood management in terms of dam operation, as it was inevitably discharged due to the inflow of flood investigations.

The Seomjingang Dam had already started to suffer damage downstream before the maximum discharge of the dam, but the flood control capacity was structurally insufficient, and the continuous rainfall caused flooding exceeding the dam's design frequency, which limited flood damage downstream by conducting discharges close to planned discharge.

Hapcheon Dam lacked technical completeness in terms of dam operation, such as not fully utilizing the dam's low-flow function and rapidly increasing the discharge volume due to the inflow of continuous flooding.

The Namgang Dam was discharged beyond the planned discharge volume of the dam management regulations, along with the structural problem of flood control, which depends on rainfall forecasting.

In conclusion, flood damage downstream areas of the dam varies by region in August last year, but it was found to have been caused by a combination of factors such as rainfall, structural problems of dams, insufficient dam management, lack of dam-to-river flood management, and lack of government. 

Need to revise manual for climate change:  

Bae Deok-hyo, chairman of the Korea Water Resources Association, pointed out, "In preparation for climate change, the dam management regulations and detailed operation manuals should be revised to improve the dam operation system."

In order to establish a flood volume management system that can reflect the increasing flood volume in accordance with the climate crisis, it is necessary to actively consider expanding flood control capacity, increasing reservoir capacity of dams, and redistribution of dam rights.

It also suggested that flood prediction models that integrate the basin with dam-river should be upgraded to improve the accuracy and speed of dam discharge.

It is said that it should push for dam smart safety management by establishing a real-time safety monitoring system, analyzing 3D images using airborne and underwater drones, and making big data on measuring data.

In terms of river management, it is also pointed out that it is necessary to come up with customized harbor measures for the catchment area to withstand extreme floods.

This is because the government should comprehensively consider increasing rainfall due to climate change, securing catchment underwater functions, expanding flood sites, and linking dam-river flood response.

In particular, in the Seomjingang River basin, active measures should be taken to secure flood control capacity.

It is also necessary to improve vulnerable areas of rivers. It is necessary to investigate all factors unfavorable to the flow of rivers, such as weak facilities such as river joins, stenosis, beams and bridges, and deposition, and to conduct improvement projects.

Major local rivers, such as direct downstream dams, need to be promoted to national rivers, and provincial rivers affected by the water level of the national rivers need to be maintained by the state.

In addition, it is necessary to strengthen the nation's flood management role to increase the capacity of tributary streams by converting local river maintenance projects transferred to local governments into state coffers.

In addition, a levee safety program should be introduced to improve inspection and diagnosis of river embankments centered on structural safety and to conduct repair and reinforcement.

Also, it is pointed out that the flood forecast needs to be upgraded by expanding flood specialist stores, establishing flood forecasting support centers, and establishing cooperative systems between agencies such as the Korea Meteorological Administration, flood control center and water resource corporation. In particular, the Seomjingang River basin should have a separate flood control center to strengthen flood management.

In the meantime, the policy direction has been changed from the existing post-recovery system to preventive measures to cope with natural disasters such as floods, but it is still lacking.

In order to prepare for climate change, it is urgent to prepare follow-up measures so that comprehensive measures can be implemented as soon as possible. 

Chairman Bae Deok-hyo said, "The government proposes to come up with concrete flood measures by considering climate change, securing low-flow functions in the basin, expanding flood sites, sub-maintenance, and linking flood response to dam-river floods." 

Implementation of follow-up measures based on the results of the investigation: 

Deputy Minister Hong Jeong-ki said, "The government offers deep condolences to the flood-damaged residents and will actively pursue follow-up measures based on the results of the flood investigation."

As a result, related support procedures will be quickly promoted so that victims can return to their daily lives as soon as possible.

The Environmental Dispute Adjustment Act was revised in April to relieve damage caused by torrential rains, and flood damage caused by water facilities such as dams was included as a target for environmental dispute adjustment.

Unlike in the past, when people had no choice but to rely on costly and time-consuming lawsuits, flood-related damages could also be quickly saved.

Among the 17 cities and counties currently affected, residents of Hapcheon-gun, Cheongju-si, and Gurye-gun applied for environmental dispute mediation.

Other regions are also preparing to apply, and it is known that they will soon apply.

Based on the results of the flood damage investigation, the government plans to actively support and cooperate with related agencies to ensure that the environmental dispute mediation process is carried out quickly in the future. 

Strengthening flood management against climate crisis: 

Second, the disaster recovery project for flood-damaged areas will also be completed quickly. Temporary restoration of major rivers damaged last year was completed before the flood period, and the restoration project is being carried out, including not only restoration of damaged river structures but also further improvement.

Of the 63 restoration works, 30 have been completed, and 33 will be completed by early next year.

In addition, seven regions, including Gurye, where the damage occurred on a large scale, are not limited to individual facilities, but are also pushing for a "comprehensive regional unit recovery project" that supports river maintenance, drainage pump installation, and land compensation as a catchment unit.

Third, flood management measures against climate crisis will also be strengthened.

In November last year, related ministries jointly established "comprehensive measures for innovation in response to wind and flood damage" and implemented them without a hitch.

In particular, in order to prevent recurrence of flood damage downstream of the dam as last year, the government has established "strengthening safety of dams and rivers" as the first of its five major implementation strategies and is pushing for countermeasures.

The dam management regulations and related guidelines have been revised in consideration of the increasing weather conditions and climate crisis.

The dam flood control communication system was introduced (previous 3 hours → 24 hours) to provide discharge information a day before to prepare local governments and residents in downstream areas for dam discharge, and the dam flood management communication meeting is also held twice in April and June.

In addition, flood forecasting branches are continuously expanding (66 to 69 special branches and 409 to 534 information provision) to provide accurate and rapid flood information. 

Strengthening the cooperation system between weather and hydrological systems: 

Fourth, additional measures will also be implemented to prepare for flood season this year.

The upper limit of each dam is set and operated by lowering the level of the dam so that flooding can be sufficiently controlled even in torrential rains above last year, and it is preparing to prevent damage to downstream areas even if two torrential rains occur in a row as last year.

The vulnerable facilities of the river and the constraints of the operation of the dam were also jointly inspected and taken measures by related agencies, and the river flow was continuously managed to prevent obstacles.

Fifth, the cooperation system between weather and hydrological gate will also be strengthened to prepare for flooding by utilizing accurate weather information.

The Korea Meteorological Administration produces and provides customized weather information for flood forecasting, and in case of heavy rain, it quickly shares accurate and detailed weather information through joint discussions with related agencies.

In addition, additional measures will be prepared that reflect the improvements proposed in this survey in parallel with the implementation of existing measures without disruption.

Deputy Minister Hong Jeong-ki said, "We will prepare port measures and detailed implementation plans by actively reflecting the improvements proposed in the survey, such as improving the dam and river management operation system, maintaining flood vulnerable zones, and upgrading flood forecasts."