Expert warns of possible flooding, landslides after Gangwon fire

A forest in Gangneung, Gangwon Province, burns down in this April 7 photo. A wildfire devastated over 2,000 hectares of mountainous terrain in five regions of the province, raising concerns over possible flooding and landslides in the upcoming summer rainy season. /Korea Times file

By Kim Jae-heun

Experts are warning about possible floods and landslides during the rainy season in Gangwon Province, where a massive blaze burned over 1,757 hectares of mountainous terrain in early April.

“Without a doubt, the province will see another natural disaster such as a flood because all the trees in the affected mountainous region were burned down,” Han Moo-young, a professor of the Department of Civil & Environment Engineering at Seoul National University, said during an interview with The Korea Times, Tuesday.

“Trees play the role of a natural dam by preserving rainwater during the monsoon. If there are areas that do not suffer a flood after a wildfire, that is because it didn't rain at all or didn't rain much.”

Han is a water expert who has been researching rainwater management for 30 years. He is currently a fellow at the International Water Association where he is chairman of Rainwater Harvesting and Management Special Group.

According to Han the ratio of total rainfall that goes unabsorbed in a forest records a level of 0.3 in normal conditions. However, the level can increase to nearly 0.8 after a wildfire and the amount of rainwater reaching flatlands from mountains can double as a result.

“It takes almost 30 years for a forest to be restored to its original condition when a huge fire damages the area. Until then, the area is exposed to disasters such as flooding, landslides and soil runoff,” the professor said.

Han strongly recommends building retention structures on the mountains to minimize possible flood damage if heavy rain falls in the region this year.

“It doesn't cost much to build retention structures as they have a big reservoir area which is very effective in storing water and preventing floods. In a recent experiment at Hongje Stream in Seoul, I witnessed retention structures reduce the chance of runoff by 72 percent,” he said.

“We cannot expect the same results with the system in any place at any time. But it is a cost-effective and efficient measure. Plus, the structures can also help prevent the spread of another wildfire.”

Last week, the Korean Geotechnical Society also urged the government to take measures to prevent possible landslides on damaged mountains in Gangwon Province as wildfires and resultant damage may have weakened ground stability.

The government estimates that the forest fire from April 4 to 6 burned down more than 2,000 hectares of land, mostly in mountainous regions in Goseong, Inje, Donghae, Sokcho and Gangneung, as well as damaging houses and facilities, and leaving 959 people homeless.

On Wednesday, the government and the ruling Democratic Party of Korea dedicated 185.3 billion won for recovery work and support for people in the affected region.