I'm busy reading the overview in The Oxford Companion to the Economics of South Africa (written in 2014), and on page 11 it says
The rand is expected to remain volatile and face depreciation risk as the United States institutes Quantitative Easing tapering.
Since StackExchange questions are supposed to show effort from the OP, here is my effort, but please don't be influenced by my ideas:
A US tightening of monetary policy could cause uncertainty of US growth prospects, and the USD is seen as a stable asset. Hence, investors seeking stability will tend to not invest in South Africa (a relatively volatile investment). On the other hand, at the time of the financial crisis in 2009, there was global instability, so the implementation of QE at that time would also have coincided with depreciation of the rand.
It's tiresome to assume any event will cause depreciation of the rand, so I was hoping you could tell me the mechanics.