I did take flooding scenario into consideration when building the farms - that's part of the reason that both SinoHash farms are built on top of existing structures of the hydropower stations, as a result, they are more than three meters elevated from the ground - bear in mind these hydropower stations cost millions of dollars so the owners have much more at stake, surfice to say that sufficient measures have been implemented with efficacy proven by the continued existence of the hydropower stations.
The material is so chosen to suit the local climate. Strong wind is extremely rare as the region is surrounded by layer after layer of mountains; since they are built on top of buildings, light weight is appreciated.