What is the cause of heavy flooding in Vinh city when it rains?

Inadequate and poor infrastructure

According to statistics from the North Central Hydrometeorological Station, in 2 days (September 18 and 19), the total rainfall measured in Vinh City was 460 mm. Compared to previous periods, the rain was predicted in advance so it did not surprise many people. Even for some drainage works under construction, this was a test to check the flood resistance capacity.Flooding of Vinh City. However, the answer is cruel and nothing has changed: Vinh City is once again submerged in water. According to our observations, in addition to the 15-17 long-standing flooded spots, this time, the number of flooded spots has increased even more than before.

Although the drainage system of Lenin Avenue from Duy Tan Street to the North Canal has been invested in and built, after only one heavy rain on the afternoon of September 18, this road section was still heavily flooded. Even until the morning of September 19, the water on Lenin Avenue had not completely receded. Photo courtesy of Quang An

Heavy rain for 2 days (September 18 and 19) in Vinh Citycausing 220 hectares of rice and 107 hectares of vegetables to be flooded from 30% to over 70%. Traffic routes and residential areas from the beginning of the city such as Hung Dong, Quan Bau, Nghi Phu, Ha Huy Tap to Quang Trung, Hong Son, Vinh Tan were all flooded. In particular, many residential areas in Truong Thi, Trung Do, Ben Thuy... were flooded from 20 - 40 cm, many areas were flooded over 50 cm deep, typically blocks 13, 14, 15, Ben Thuy ward; block 2, Truong Thi ward, Vinaconex 9 villa area, Ha Huy Tap ward had 110 households flooded nearly 1 meter deep. The total estimated damage was 6.34 billion VND.

(Excerpt from the report of the Flood and Storm Prevention and Control Committee of Vinh City)

This widespread flooding is not only directly caused by the heavy rainfall in a short period of time, about 200 mm of rain in 2-3 hours, but also by the influence of the storm. Before the rain, there was strong wind causing leaves on many streets to fall, when it rained, it blocked the mouth of the sump pit, causing the flow to be blocked.

During the flood, many of us reporters were at the scene so we clearly saw this phenomenon when many streets such as Duy Tan, Dinh Le, Nguyen Van Cu, Nguyen Thai Hoc, Le Hong Phong... the road surface above was flooded but the drainage below had little water and weak flow, we had to scoop up the trash above the mouth of the collection pit so that the water could flow down. The problem was that while heavy rain caused severe flooding, the Cua Nam Pumping Station had no water to pump because the water in the regulating lake was too little, so we had to pump sparingly.

Nguyen Van Cu Street near the intersection with Le Hong Phong Street continues to be a major flooding point every time it rains heavily. Photo: PV

From actual observations, we have found that although the drainage system has been upgraded, it is still inadequate and weak, so it has not met the requirements of flood prevention and control in the new context. Specifically, the drainage system atNai bridgeThe drainage ditch on Thong bridge to Vinh Tan regulating lake is too small; the drainage ditch on Le Nin Avenue, from the Provincial General Hospital to Bac canal is too far and small, leading to very slow drainage...

A car stalled on Nguyen Tai Street (near Nai Bridge culvert) on the night of September 18. Photo courtesy of HC

"In addition, although they have been maintained and repaired, once again, when operating, Ben Thuy and Cau Den Pumping Stations encountered a problem with a power outage for more than 30 minutes and because there was no backup generator, the amount of rainwater rose quickly. Fortunately, the rain stopped quickly afterwards, otherwise if it had rained for a few more hours, Vinh Tan, Hong Son areas and especially Vinh market would have been flooded as badly as in 2019 and the damage would have been huge" - a representative of Vinh Urban Management Department added.

Regularly dredging sumps will help limit flooding during heavy rains. Photo: PV

Previously, Vinh City People's Committee established 2 working groups to review, inspect and remind the Flood and Storm Prevention and Control Command Boards of key wards to strengthen their responsibility for urging; at the same time, review and urge the People's Committees of wards and communes to speed up the progress of construction works before the rainy and stormy season, including drainage items. As for Vinh Urban Infrastructure Management and Development Joint Stock Company, according to the plan, they organized dredging of collection pits and some drainage ditches before the storm arrived. Although there was a flood and storm prevention plan quite early, when heavy rain occurred, many streets were flooded and the main reason was that the mouths of the collection pits were full of garbage, fallen leaves were blocked and after working hours plus it rained at night so it was not possible to mobilize human resources to handle...

More fundamental solutions are needed.

Mr. Nguyen Ngoc Phong - Deputy Director of Vinh City Construction Investment Project Management Board shared: Due to the impact of climate change, weather conditions are increasingly unusual and to limit the riskfloodAlong with urgent investment solutions, there needs to be a long-term and fundamental solution for the city.

Construction of drainage ditch on Le Viet Luong street connecting to drainage ditch on Le Hong Phong street in Hung Binh ward. Photo: Nguyen Hai

Currently, Vinh city has 3 large capacity pumping stations, each station consists of 6 units located in 3 areas: Cua Nam, Ben Thuy and Vinh Tan, of which Cua Nam regulating lake pumping station has a total pump capacity of 18,660 m³/h; Black Bridge Pumping Station, South at Vinh Tan regulating lake, pump capacity is 56,000 m³/h and Southeast Pumping Station at regulating lake No. 3, Tri bridge, Ben Thuy with capacity of 20,000 m³/h. Although regularly inspected and maintained, because the pumps are too old, the actual pumping capacity does not meet the design and when there is a flood, the operation process continuously encounters power problems.

Construction of Thanh Thai road in Hung Phuc area is still unfinished, so heavy rain causing flooding will be very dangerous for people. Photo: NH

Statistics from the Vinh City Flood Control Steering Committee show that: In the 2017 flood, the pumping station in Cua Nam Lake was connected to the Hung Nguyen power system. When it rained and flooded, Hung Nguyen lost power, causing the station to lose power and not be able to pump. In October 2019, during the historic flood, Ben Thuy pumping station was too low and flooded, so it could not operate. In 2020, although it was repaired, during the first flood control operation, 2/3 of the pumping stations lost power for more than 30-60 minutes without a backup generator. The above reality shows that the pumping stations really need a generator to backup in case of a power outage. The company has made many recommendations, but due to the large capacity generator and high cost, there has been no investment source.

Mr. Dinh Tien Dung - Director of Vinh Urban Infrastructure Management and Development Joint Stock Company

In addition to the above solution, to prevent flooding and handle the phenomenon of slow drainage, based on the survey of the drainage system from Le Nin Avenue, the section from the Provincial General Hospital to the North Canal is too long (over 5 km) and some other routes, Vinh city is proposing that the province invest in upgrading the drainage system from the Provincial General Hospital to the North Canal because the previous drainage system had a small aperture (radius of about 1m) so the drainage was slow; especially the section adjacent to the irrigation canal from Hung Dong commune to Nghi Duc commune, the drainage canal must be siphoned, curving down below the irrigation canal, so every time it rains heavily, it causes congestion and very slow drainage. In the recent rain, while in other areas, the water receded after 1-2 hours, the area of ​​Le Nin Avenue, in front of the Provincial General Hospital to Vinh airport was still flooded until the afternoon of September 19.

Workers construct the drainage ditch west of Duy Tan Street connecting to the drainage ditch on Le Nin Avenue. Photo: PV