Dig a new drainage ditch where he comes through, nice and wide & deep and filled up to the top . or you could get nasty and dig a hole 1 foot deep 1 foot round with a barbed metal spike in the center , he won't want a second dose of that, the Vietcong used sharpened bamboo barbs dipped in sewage to ensure infection, there is also the ankle breaker , instead of spike use a foot of broom handle buried for 6 inches in the hole , the victim drops in the hole and his foot rocks on the broomstick snapping the ankle . But then I'm just a vindictive old sod, nail boards are very effective at deterring unwelcome visitors.