The statement is correct.
When a flood is giving a time-bonding term, such as the 100-year flood, in this statement, it means that it has been noticed that the floods from the particular river occur on approximately that much of a time span.
If there has been a flood recently, than it most probably means that there isn't going to be a flooding caused by that river for the foreseeable future.
Now, there's always exceptions, as the climate patters are changing constantly, and there's always surprises, but in general, in lot of regions of the world, there has been noticed a certain consistency in some natural occurrences.
Heterogeneous most generally means consisting of different, distinguishable parts or elements. The word is used in a more specific way in the context of chemistry to describe a mixture consisting of two or more different substances or the same substance in different phases of matter (such as ice and liquid water).
The maharaja (local ruler), Hari Singh, initially wanted Kashmir to become independent - but in October 1947 chose to join India, in return for its help against an invasion of tribesmen from Pakistan.
Today, Delhi and Islamabad both claim Kashmir in full, but control only parts of it - territories recognised internationally as "Indian-administered Kashmir" and "Pakistan-administered Kashmir".
Hope this helps!
