The river, watching and waiting

Yesterday Jeremy Iron's read Eliot's Four Quartets on Radio 4.  There are parts that I don't understand at all, but then others leap into life.  After the floods the beginning of The Dry Salvages sounds like a prophecy fulfilled:-

I do not know much about gods; but I think that the river
Is a strong brown god - sullen, untamed and intractable
Patient to some degree, at first recognised as a frontier;
Useful, untrustworthy, as a conveyor of commerce;
The only a problem confronting the builder of bridges
The problem once solved, the brown god is almost forgotten
By the dwellers in cities - ever, however, implacable
Keeping his seasons, and rages, destroyer, reminder
Of what men choose to forget. Unhonoured, unpropitiated
By worshippers of the machine, but waiting, watching and waiting