you are right. However, because of Global Warming as well as the residents are being loosed their mainland for living and irrigation . Thus, floating house can apply not only for Mekong river'resident also for other flooding areas.
In my opinion, this housing style should be applied in some places like the middle areas of Vietnam which frequently occurs floods, and maybe Mekong river also likes that. If you can address its problems, you can plan this housing style become the floating city ( ex: this kind of city was in China). following the change of water level, the floating houses can be separated or connect into group.
If I have more information I'll continue to discuss with you.
thanks for your answer.your idea is helpful for me. But there is one thing may wrong that is floating house cannot apply in the middle of Vietnam.Because this area has complex topography, so river flow is faster and stronger than Mekong Delta.