We are happy to hear that you know snakes are an important part of the ecosystem and should be left alone. Most of them are harmless and actually quite shy, in that if they hear you coming they will retreat. (I guess they don't want to see us any more than we want to see them!)
Several types of snake repellents have been used in the past, but
none has been consistently effective, so we generally don't recommend them. If you choose to, always apply 
according to label directions. 

There are other ways to deter snakes from being in areas where you don't want them. Moving brush piles and locating wood stacks further from the house or play areas is recommended. Snakes do not usually travel very far. Most have specific habitat
and range preferences. In general, snakes like cool, damp, dark
areas where they can hide out during the hottest time of day.
During the early part of the day they may move into a sunny
spot to warm up. Snakes are most active at dusk and early in the
morning. 

During new construction, natural habitats are disturbed
and snakes are forced to move into new areas. Snakes are
especially attracted to fire wood stacked directly on the ground,
old lumber piles, junk piles, flower beds with excessive mulch,
weedy gardens and boards or other items lying on the ground.
To discourage snakes from coming close to a building or house,
remove these hiding places from the property. While this will
not eliminate snakes, they will not be able to find comfortable
habitats close to buildings.

Here is our page on snakes: https://extension.umd.edu/hgic/topics/snakes

Christine