Sentence:  Floods in northern India, mostly in the small state of Uttarakhand, have wrought disaster on an enormous scale. The early, intense <WSD>onset</WSD> of the monsoon on June 14th swelled rivers, washing away roads, bridges, hotels and even whole villages. Rock-filled torrents smashed vehicles and homes, burying victims under rubble and sludge. 
Meaning of the word marked with <WSD> tags:  A setting about; a beginning.