Searching for the culprit causing severe flooding in Hoang Mai town (Nghe An)

Operation of Vuc Mau Lake

From September 28 to 30, in the areaHoang Mai townThere was heavy to very heavy rain combined with Vuc Mau lake opening 3 spillways and rising tides causing flooding, damage, and loss of many production areas and people's houses.

Of which, 19.4 hectares of summer-autumn rice of Quynh Di ward and Quynh Loc commune were flooded; 479.5 hectares of winter-spring vegetables were flooded and damaged, with over 70% damage; more than 460 hectares of aquaculture area were flooded. In addition, 3,385 households had their houses flooded, 144 households had to be evacuated...

However, many people wonder why this year Vuc Mau Lake also opened 3 spillways, the same as in 2021, but the damage that Hoang Mai town had to bear was heavier than last year?

Accordingly, in 2021, due to the impact of storm No. 6 from September 23 to September 26, in Hoang Mai town and the upstream area of ​​Vuc Mau lake, there was heavy to very heavy rain, the lake water level reached +21.61m, the lake bed in Tan Thang commune (Quynh Luu) had 19 households with water flooding up to their yards.

At that time, Vuc Mau lake opened 3 spillway gates, 188 households were flooded, of which Quynh Vinh commune had 35 households, Quynh Trang 115 households, Mai Hung ward 25 households, Quynh Thien ward 13 households. Of these, 103 households were subject to relocation.

Vuc Mau Lake is a level II irrigation project, located in Quynh Luu district and Hoang Mai town. The lake's basin area is 215km2.², in which the normal water level is 21m and the reinforced water level is 22.72m. This lake was built in 1978 with 3 initial sluice gates, and in 2010, when upgraded and repaired, it was expanded to 5 sluice gates.

According to the Vu Mau reservoir operation log, at 7:03 p.m. on September 23, at this time, storm No. 4 had not yet made landfall, there was rain in the Vu Mau reservoir basin, the lake water level reached +20.05m, exceeding the level of the anti-destruction line, so the operating unit adjusted the opening of spillway No. 5 to 3.42m.

After opening 1 spillway, the lake water level dropped to +19.90m, below the allowable anti-flood line elevation of +19.93m. Since that day, 1 spillway gate has been continuously opened, until 19:20 on September 28, after storm No. 4 made landfall, due to heavy rain in the Vuc Mau lake basin, the lake water level reached +20.44m, exceeding the anti-flood line elevation, so the operating unit continued to open the 2nd gate to discharge flood (gates No. 4 and No. 5).

At 1:28 a.m. on September 30, the water level of the reservoir reached +21.36m, there was very heavy rain in the basin, so Hoang Mai Irrigation Enterprise adjusted to open 1 more spillway gate to discharge flood (opened 3 gates: No. 1, 4, 5). The opening of 3 spillways took place continuously from September 30 to 1:02 a.m. on October 1, due to the decrease in rain in the basin, the operating unit adjusted to gradually close the spillways, until today it continues to operate 1 gate to discharge flood.

Regarding the question of whether the flood in Hoang Mai town was caused by the release of floodwaters by Vuc Mau reservoir, Mr. Vo Sy Thang - Deputy General Director of Bac Nghe An Irrigation One Member Limited Liability Company said: At this time, there was very heavy rain in the area, so blaming Vuc Mau reservoir for releasing floodwaters causing severe flooding is incorrect. Because in 2021, the operating unit also released all 3 gates, but the number of flooded households was only 188 households. In addition, before storm No. 4 made landfall, the unit also proactively released floodwaters, when the water level in the reservoir had not yet reached 21m - the normal water level, or even 22.72m - the flood cut-off level.

Looking for the cause?

Mr. Thang also explained that Vuc Mau Lake was built in 1978 with 3 spillways, and in 2010 was upgraded to 5 spillways. The problem is that the Hoang Mai River from the spillway down to Lach Con has a very large silted bed, but it has rarely been dredged or widened to increase the flow. Not to mention that every year there is always encroachment on the river and some locations where bridges are built across the river do not clear the riverbed, causing blockage of the flow when releasing floodwaters.

Besides, although the flood cut-off level of the reservoir is 22.72m, in reality, the unit never reaches this level when operating, because if it reaches 22.72m before releasing flood, it will cause 512 households in Tan Thang and Quynh Thang communes (Quynh Luu), who cannot be evacuated at this time, to be deeply flooded.

After the historic flood in 2013, Hoang Mai town proposed dredging the Hoang Mai riverbed and investing in building dikes on both sides of the river, from the end of Quynh Trang commune to Lach Con, and relocating 512 households upstream, but to date it has not been implemented.

According to the 2022 disaster response plan report of the Bac Nghe An Irrigation One Member Limited Liability Company, which has been appraised by the Department of Agriculture and Rural Development: Currently, in Hoang Mai town, the North-South expressway is under construction. During the construction of piers and temporary bridges, rocks and soil are scattered into the riverbed, narrowing the cross-section of the Hoang Mai River, affecting flood discharge when Vuc Mau Lake overflows.

Specifically, on June 1, 2022, Hoang Mai Irrigation Enterprise sent a document to Project Management Board 6 - Ministry of Transport; Hoa Hiep Company Limited, Truong Son 185 Joint Stock Company, Trung Chinh Construction Trading Company Limited. This document clearly stated that, through inspection of the Hoang Mai River route, there are two works under the North - South Expressway project under construction on Hoang Mai River at the location of Hamlet 4, Quynh Trang Commune (South) and Hamlet 3, Quynh Vinh Commune (North), which are the material transportation route constructed by Hoa Hiep Company Limited and Truong Son 185 Joint Stock Company; Hoang Mai 2 Bridge constructed by Trung Chinh Construction Trading Company Limited.

The construction of the bridge requires expanding the foundation, abutments and building a road for transporting materials. The construction unit has blocked the river, allowing water to flow only through a 12m wide temporary bridge, which will cause congestion (the Hoang Mai River's aperture at this section is up to 60m), and affect flood and storm prevention work in 2022. When there is a storm, the Vuc Mau reservoir must be discharged, which will increase flooding and block the flow of the Hoang Mai River.

After that, Hoang Mai Irrigation Enterprise continued to send documents to the above units many times with the same content as above. However, the dredging and clearing of the river was still not carried out. After that, the Vuc Mau Lake management unit had to send documents to the Provincial People's Committee, the Department of Agriculture and Rural Development, the Irrigation Sub-Department and related units, because through inspection, at the construction site of Hoang Mai 2 Bridge, the upstream and downstream water levels where the riverbed was filled differed by more than 0.5m.

On September 26, Nghe An Department of Transport presided over and coordinated with relevant departments, agencies and sectors to inspect the scene. On September 27, the Department of Transport sent a document to Project Management Board 6 - Ministry of Transport, directing the contractor to focus on mobilizing vehicles, motorbikes and equipment to urgently clear and clear the flow of Hoang Mai River at the mid-stream and south of Hoang Mai River to ensure drainage, avoid flooding, affecting people's daily life, production, safety of life and property.

However, at 2:00 p.m. on September 27, when storm No. 4 was about to make landfall, there was heavy rain in the area. After checking the scene, Hoang Mai Irrigation Enterprise still did not see the construction unit completely clearing and unblocking the flow.

In particular, by September 28, when storm No. 4 had made landfall, the Northern Irrigation Company Limited had Report No. 839/BC.KT-CT reflecting: "By September 28, 2022, through inspection and reporting by Hoang Mai Irrigation Enterprise, at the construction site of Hoang Mai 2 bridge, the temporary bridge road at the location between the river and the south of Hoang Mai 2 bridge has not been processed and cleared of soil and rock as committed in the working minutes".

On October 5, from National Highway 48D, following the residential road, we arrived at the North bank of the Hoang Mai River, where the Hoang Mai 2 Bridge on the North-South Expressway passes through. At this time, the water gradually receded, and the Hoang Mai River bed revealed land mounds and concrete blocks that the contractor constructing the North-South Expressway had not completely cleared.

In addition to the service road blocking the Hoang Mai River, the area near Lach Con, the section near Quynh Phuong Bridge and the Nha Le Canal section where the coastal road passes, the construction unit also built a service road, affecting the flow.

Mr. Pham Van Hao - Vice Chairman of Hoang Mai Town People's Committee said that Nha Le canal is the drainage area for the area from Quynh Vinh commune, near the end of the canal, the coastal road construction unit had built soil across the canal, so water flooded into the shrimp farming area of ​​the people. It was not until the morning of September 30 when the flood water had risen, inundating many localities in the area, when the town had comments, that the construction unit proceeded to bring in excavators to break the road and clear the flow.

Is it possible that the recent severe flooding in Hoang Mai Town was partly caused by the construction of the two above projects?

Besides, many people believe that after being separated from Quynh Luu district, the drainage system in Hoang Mai town has not been invested in synchronously. While Hoang Mai river is the main river, draining water for Vuc Mau lake, it flows around the town, the lack of dredging and dyke reinforcement has made the risk of flooding in this locality more and more serious.

It is known that in 2020, the Provincial People's Committee issued a decision approving the Feasibility Study Report of Sub-project 3: Improving Hoang Mai urban infrastructure, under the Urban Infrastructure Improvement Project to minimize the impact of climate change for 4 coastal provinces of North Central Vietnam, using loans from the French Development Agency.

Many people hope that when this project is implemented, the wastewater drainage system as well as the drainage system during the rainy season in Hoang Mai town will be somewhat improved.