Below are suggestions to keep cats off of your property, it is illegal to harm them.
Eliminate food sources: Ensure that all household trash and leftover food are placed in trash bins with secured lids.
Block off access: Cats seek out dry, warm shelter away from the elements. Block off access to the places in which you don’t want cats (making sure no cats are inside before doing so). The Animal Services Division receives many calls for female cats with kittens living in a window well. Window well covers can be purchased at local hardware stores for as little as $20. They can also keep out leaves and debris, prevent water from entering basement windows, and provide extra security and energy savings while still allowing people inside the home to safely exit in an emergency.
Smells that repel cats: To keep cats out of yards or gardens, plant the herb rue or sprinkle dried rue. Citrus or lemon scents, garlic, ammonia,vinegar, coffee grinds, pipe tobacco, mustard, citronella, or eucalyptus all deter cats as well. The scents diminish over time, so re-applying is necessary.
Deterrents for digging: Push chopsticks into small potted plants. Use pinecones, lava rocks, concrete pavers or stones as mulch to prevent cats from digging. Place upside-down carpet runners in landscape beds.
Commercial Deterrents (available online):
ScareCrow: This motion-activated sprinkler has an infrared sensor that releases a three-second blast of water. The sprinkler “fires” 1,000 times on one nine-volt battery and covers an area 45 by 35 feet long.
CatStop: This motion-activated, ultrasonic alarm emits a high-pitched sound that repels cats, but can’t be heard by humans. A nine-volt battery can operate up to nine months, depending on usage.
CatScat: These harmless mats or carpet runners are made of flexible plastic spikes. Place on the ground with spike side up to discourage cats from digging.