Flooding in Seoul

The summer monsoon in Korea begun this year later than expected. Until now the rain amount wasn’t high in Seoul. Usually as soon as the monsoon rain begins, news reports about strong winds, traffic accidents and flooding become more frequent. Especially, urban flooding is a serious issues in Korea. This blog post is going to look at Seoul’s countermeasures to urban flooding.

Seoul experienced heavy floods in July 2011. During the monsoon season there have been land slides and flooding in the city. 69 people got killed or went missing. The damages were caputred in pictures of the floods. Focusing on Gangnam, there was 70 mm of rainfall occurred in 1 hour and a total of 400 mm during the whole day in July 2011. The subway stations and streets were flooded. 1,214 shops or homes were affected and 171 billion KRW estimated damages. Seoul reacted with a couple of measures on the local and national level.

 

 

Reasons for Flooding in Seoul

A big issues of cities in general is that everything is covered with built structure. In Seoul around 47% of the total administrative land area is concrete or asphalt. The following map shows the percentage of covered land for each block:

So from this map we can see indirectly the high risk areas regarding heavy rain fall. As it was mentioned earlier, Gangnam area is under risk. Over 90% of the land is covered in concrete there. Then you have areas like Sindorim as well as Eunpyeonggu, Jungryanggu and Junggu (downtown) with a closed concrete surface.

 

 

Seoul Urban Flooding Countermeasures

Korea and especially Seoul are well aware of the problem. They acknowledged that handling floods is an important feature of urban resilience. So Seoul aims to employ diverse measures:

Cleaning of storm drains – The easiest way to deal with rainwater is to let it get down to the gutter and disappear in the sewage system. But many drains are filled with cigarette butts or leaves. Seoul sends out more employees before and during the monsoon season to clean the gutters.

Increase capacity of storm drainage system – Korea’s storm drains can hold a maximum of 75 mm rain per hour. The Korean government made an action plan in 2012. It is called the “Comprehensive Plan on Sewage Maintenance against Urban Flooding”, where 60 areas will be designated as risk sites and undergo capacity increase until 2017. Seoul invests 1.8 trillion KRW to increase the capacity of sewage to 95 mm per hour. Here’s a map of the priority sites in Seoul:

Storm sewers will be constructed in 33 places in the city. Seoul builds big storm water tunnels in the underground. One of them is a 4.5 km long tunnel ending in the Anyang stream:

Green rooftops – A help to the issue are rooftop gardens that save rain water. Already since 2002 Seoul promotes the establishment of green rooftops and there have been 550 garden rooftops in the city in 2012.

Management of mountain rain runoff – A strong rain fall within a short time makes it even difficult for the green spaces, such as mountains, to absorb water. Rainwater then flows as surface runoff down the slopes. Seoul is in the process of constructing rain gutters in order to better control the runoff.

Disaster risk management – In case of a natural hazard Seoul wants to establish a center to coordinate actions, monitor the situation and inform citizens.

 

 

Seoul Urban Flooding

The disaster in 2011 showed that Seoul has to be ready for extreme high amounts of rainfall. This year’s monsoon rain wasn’t yet very strong. As climate change is going to cause severe weather phenomena, we can also expect more flooding in cities. Seoul identified a couple of measures to increase the resilience but the city hasn’t been put under stress of a natural hazard. The next heavy rainfall may show us the effectiveness of Seoul’s urban flooding countermeasures.

 

 

Resources: SBS News | Seoul Landuse | Seoul Presentation