I would like to write about a different aspect of the flood - how the people died. As with the cause of the flood, I can only speculate, but I base my opinion on how the flood in Jirisan at the end of July, 1998 caused so many deaths.
First, the six Koreans (South Koreans, from the Herald article, I see a child presumed to be North Korean has also been found) were camping by the river.
The problem is, what does "by the river" mean? For the deaths caused by the Jirisan floods it meant actually on dry sections of the riverbed itself. I was unable to find much online about the 1998 flood but Kushibo linked to a Sally Ann article. People had even parked their cars on the riverbed. I had hiked along the river at some time before the flood and know that signs existed warning people not to camp "by the river".
If the victims of the recent flood also camped on exposed portions of the riverbed, I don't want to directly compare them to the Jirisan victims. The flood in Jirisan was caused by a fairly major typhoon and the campers should have put a little thought into their choice of campsite considering the heavy rain. There was no such warning at Imjin: from the above-linked Herald article: Speculation rose over what was behind the unusual discharge which came without notice when the area saw almost no rainfall recently.