If the fence goes all the way round your veg patch then all you would have to do is net the top of the area with cheap bird netting - if you can't let your chucks into direct contact with your veg then you don't lose anything by netting the top and getting a few ducks too.
They won't be able to...
I used to have a lovely green garden; then I got ducks.
Now I have a lovely brown garden!
Ducks are worse for garden destruction than chucks - and if you have calls, mallards or other flighted breeds then they may well fly over low fences to get at the goodies on the other side; even when...