It appears though that there's very little new in this documentary. I first came across the idea of the plagues being some sort of chain reaction over ten years ago. There might be some new information in this (perhaps that they were triggered by a sudden prolonged dry spell) but the core of the theory (including the possibility that a volcano was responsible, go a long way back.
Personally, while I used to be attracted to such theories, I find them a little too neat these days. It seems reasonable to me that a series of events may have lain behind the Exodus, but whther there were exactly ten plagues which occurred exactly as the final text of Exodus records seems a little unlikely / unimportant to me, particularly given the different sources behind the plagues seem to recall fewer in each instance (as far as I recall).There are also a number of other National Geographic documentaries showing through April from their "Mysteries of the Bible" series, including The Birth of Jesus, Jesus the Man, Jesus: the Healer and Jesus the Preacher which all air on Good Friday (2nd April), and one on Revelation that airs on Easter Monday (5th). Parts of these seem to be available to view online (even in the UK) though most of them seem to be repeats.