Posted: 15/09/2017 at 07:56
First you need to clear the area and sort out underlying problems. Is the flooding a long standing problem? ie is there a ditch there or has one been filled in? Ivy in a hedge does not usually kill it. I have Ivy in a hawthorn and holly hedge. Holly and hawthorn can be clipped hard and will come back from neglect in a year or two. If there is too much Ivy, cut it off at floor level, and let it die off before pulling out.
If it is all dead, then clear out all the roots, add soil conditioner such as compost and some bonemeal and replant with young plants about a foot apart. If it is a long hedge, then match in with what you have got. If it is all of the hedge, you can choose something different. Maybe variegated holly plants, again a foot apart, wtll knit together to form a dense hedge.