First of all, there is no reason to be very scared. You have lived there for 16 years and haven't had an issue with a venomous snake prior to this time. The venomous snakes have been there all of those 16 years and haven't caused a problem.

If you have to deal with a venomous snake once over 16 years or so, I think you can feel pretty safe. Just because you have seen one now doesn't change anything.

Snakes go wherever their basic biological needs are going to be met, just like butterflies do. The snake was obviously in the kennel because there was either food, or water, or shelter there. Remove those sources of shelter and food and the snake won't be back.

Rats or mice living in or under the kennel? Seeking shelter under the kennel? Clean up any attractants for rodents and fill in any holes under the structure and any paving and you should make it unattractive to both rodents and snakes.

Rattlesnakes are good ratters - maybe a bit difficult to deal with mentally, but I've been on a couple of ranches that had rattlers living under their feed sheds. The rattlers were well-fed, the feed was safe from vermin and the ranch hands stepped cautiously around the snakes when they were sunning themselves on the steps.

I almost had a heart attack when I stepped out and realized what kind of snake I had just stepped over. I was accustomed to seeing various snakes around feed sheds, usually "bull snakes", so I barely glanced at them.