Awareness Of Typhoon Risks In Mekong
By Dr. Le Tuan Anh, Dr. Hiroshi Takagi 20 October, 2020
Vietnam is vulnerable to typhoons yet awareness & preparedness are insufficient. Dr Anh & Dr Tagaki unpack why
Vietnam is frequently hit or affected by typhoons that 80% of disasters in the country are typhoon related (induced). There were approximately 786 typhoons that approached or affected Vietnam during the twentieth century. These storms generally hit the mainland, especially coastal provinces in the north and the center of Vietnam, while the Southern part is relatively less affected by typhoons.
80% of disasters in Vietnam are typhoon related…
…climate change will bring more & at stronger intensities
Recently, the Ministry of Natural Resources and Environment of Vietnam (MONRE) announced that there will be an increase in the number of high-intensity typhoons affecting Vietnam due to climate change. Normally, the typhoon season spans from June to November and the peak occurrence of typhoon landfalls varies across regions (October for the central part & November for the southern part). Yet, it is predicted that typhoon tracks will move southward and typhoon seasons will stretch longer.
This change of patterns will substantially increase the vulnerability of local communities to storm surges, which is already high before as the coastal area in Mekong Delta has an average elevation of only about 1m above Mean Sea Level, making them vulnerable to even relatively small surge heights.
According to the statistic from MONRE, 2003, 2009 that summarised from a number of Vietnamese reports and articles, the higher number of typhoons in the context of climate change could lead to growing concerns over the threat posed by typhoons, especially in the Southern part of Vietnam, Mekong Delta.
People’s perception on typhoon disasters from field surveys in the Mekong Delta
For a successful evacuation plan to take place, in addition to a warning system, the local population must be aware of the dangers posed by the disaster and understand what measures to take when it strikes.
To assess the perception of the Vietnamese people, a series of field surveys using questionnaires were conducted in many small towns along the coastline of the Mekong Delta and the remote Con Dao island (right figure). Selected locations have been directly affected by the previous typhoon and the majority of them are undeveloped rural areas except for Can Tho city.
The purpose of the survey was twofold: (1) identifying the damage caused by past typhoons and (2) understanding disaster awareness of the inhabitants. The field surveys revealed the perception of local citizens in Southern Vietnam on typhoon and provided the information in terms of how they prepare to cope with such disasters (below figure).
How do local people think about the risks?
The field survey showed that the local population has a high degree of awareness of the dangers posed by those events. Typhoon Linda (1997), which caused catastrophic damages, is the most unforgettable event that significantly affected local people’s perception of typhoons.
Typhoon Linda (1997) significantly increased local people’s awareness…
Linda is considered to be the worst storm to have hit the southern part of Vietnam in the past several decades and killed more than 3,000 people. However, part of the respondents did not recall Typhoon Linda. This phenomenon is especially significant amount young respondents who were born after the event and those who had only migrated recently from other areas that were not present when typhoon Linda struck.
The overall level of disaster awareness still insufficient
Despite the relatively high awareness towards storm surges, the preparedness in Mekong Delta and Con Dao island seems to be inadequate to cope with the potential risks.
…but preparedness levels in the vulnerable Mekong Delta are is inadequate
Even though several evacuation drills are conducted annually, only a small group of people took part in these drills in the last 5 years. It is noticeable that as participation was not mandatory, the majority of attendants were still limited to local governments and a small group of local residents.
The fact that many respondents admitting that they do not know how to evacuate in case of disasters is a strong evidence that the local people are very vulnerable to future typhoons.
Typhoon Linda 1997 and its severe damage revealed through numerical simulation
Although Linda was more than 20 years ago, few studies have examined the extent of damages caused in Vietnam. In particular, the physical impacts of storm surges and high waves have yet to be scientifically investigated. Limited availability of information of Linda may also be due to the limited mobility of international researchers at the time; specifically, the internet environment was insufficient to promptly conduct post-disaster surveys abroad.
Impacts from typhoons have yet to be scientifically investigated
In this situation, numerical simulation could be the solution to understand how severe were damages caused by Linda. The coupled storm surge – wave simulation using Delft3D model is implemented in the case of Typhoon Linda (1997) in Southern Vietnam in order to reveal the extensive damages. The results showed that the wind-generated waves off Con Dao island—which served as a shelter for fishermen—were estimated at 8m high during Linda’s passage (below left figure).
According to interviews with local residents, many fishermen were still out at the sea when Linda approached the East Sea. Fishermen did not seriously consider any risk that they might encounter because such a natural disaster rarely occurs in this region. As a result, many wooden boats might have been caught by Linda at sea, despite attempting to escape from the typhoon’s path. Meanwhile, the abnormal water level reached 1-2 m in the Mekong Delta (above right figure).
Lessons from typhoon Linda
It is well known that communities in low-lying areas in the Mekong Delta is particularly vulnerable to any type of flooding events, whether it is from the river (overflowing due to the combination of high tide and heavy rainfall) or from a typhoon-induced storm surges.
Also, the insufficient structural strength of houses means that many roofs were blown away during typhoons, which is the most common type of damage in the Mekong Delta. Strong wind combining with heavy rain will also cause flooding in places adjacent to the riverbank while there is no noticeable damage recorded in higher areas and further inland.
According to the questionnaires, the majority of respondents confirmed that they started to become aware of the risk from typhoon disasters only after experiencing typhoon Linda. Overall, the level of disaster awareness in Vietnam is not stable although this could be reinforced by recent events and will probably change over time.
Another strong typhoon Tembin (2017) with a sustained wind speed of up to 70 knots (according to Japan Meteorological Agency) approached the East Sea with a similar track as Linda’s and it could be the strongest typhoon since Linda struck in 1997 (below figure). Fortunately, local people paid more attention this time and better prepared for this event even though it eventually did not land in Vietnam.
Due to such low frequency of typhoon occurrence in the Southern part of Vietnam, the awareness of disaster probably fades over time
Due to such low frequency of typhoon occurrence (around 20 years) in the Southern part of Vietnam, the awareness of disaster probably gradually fades over time. This could however be improved if appropriate educational efforts are made. The preparedness against coastal disasters, especially in terms of disaster drills, as well as the coastal disaster education for fishermen and younger generation, needs to be improved.
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