In the same situation Neighbour has 10 cats moved in few months ago the cat used backyard as a kitty litter , u have to make it as unpleasant and a inconvenience to come in definately try getting close enough to hose them (I can't since they r mainly feral n take off when the c me) , 1st I boarded up all the holes in the fence if ther is allot of dirt in back yard cover with chicken wire until grass grows since they like to poop in soil n dirt, if u hav friends with citrus trees(lemon lime orange ect) grab hole bunch put it blender rinds and all and sprinkle it over ground round fence line and dirt patches(cats hate the smell) n they might go elsewhere nicer any leftover stick in fridge or freezer for next time , also I use cheap water crystals n soak them in citronella or citrus oils n sprinkle them round too (cheaper then get off my garden) doesn't last as long but u get 10 times as much out of it also with the windows put vasoline with powdered pepper mixed in on the outside sills when cat comes through it gets it on his feet then when he cleans them he gets awful taste n remembers where he got it frm and won't want to go back there . All these things are harmless n worth a try before u trap it . They seem to b working for me ATM good luck