The pictures of the flooding were shown over here. One scene that struck me was a shot of 3 or 4 police officer walking calmly towards the camera, while 10 metres behind them the coastal road they had just walked across collasped . They seemed tottally oblivious to the danger.
Back to your post. I'm not sure who is to blame for building the houses. In this country you need to get planning permission to build any type of building. The developers would have to get permission off the local authorities. Both would seem equally liable.
Then there is the question of caveat emptor. If I was buying or building a house on a hill side or coastal area it would be in my best interest to get the house and the plot of land surveyed, so I would know it wouldn't be washed away in the first heavy rain of the season.
Seems incredible that it could happen in the first place.