A storm drain is the thick, metal grating you see along the side of the road that is approximately 1 foot wide by 1 foot deep. Storm drains are maintained by your town or city municipality to deal with rainwater but not waste. While the storm drain system in your area may seem basic in its function, there are several advantages and disadvantages to these drains.
A storm drain's primary purpose is to give the rainwater a place to go as opposed to collecting in the streets and, potentially, flooding your home. By removing the run-off water, the storm drains take it off the road, making it safer to travel on. Storm drains also help reduce the amount of ice on the roads by giving run-off water a place to go during midwinter thaws.
Rainwater that does not have a storm drain to flow into will continue to build up until it finds a place to go. An advantage of storm drains is that they give the water a place to flow out of your driveway and your yard so it doesn't build up and flow into your home.
The water that runs into a storm drain does not go to a water treatment plant. Storm drain water is directed to the nearest water source to reduce the water level in the streets and around homes. This sounds ideal until you realise that lawn chemicals used to kill weeds and bugs run off your lawn, onto the street, down the storm drain and back into your local water supply. The same thing happens when people dump chemicals into the storm drain because it looks like a disposal area.
While storm drains offer a way for rainwater to escape from city streets and front yards, they are still just metal grates in the street. Debris from the run-off water can easily clog storm drains and render them useless. Unless there is someone out there constantly cleaning off the storm drain grate during a storm, the grate may reach the point where it is not a help but rather a cause of water build-up.