Good question. It's called jet blast. Sorry, BAe146 data not to hand right now. You need the manufacturer's data. Quite possible to get damage at 60m. Depends on the aircraft thrust setting (was it 'stand on brakes and open throttle' OR a more gentle rolling start?).
See this for the 737-800 jet blast envelope:
737-800 jet blast. Possibly the BAe146 blast is 50% of the 737-800. Above 80 kph is when damage occurs.