Yes, it will overflow and drain off somewhere as rainwater usually does!!!

Not really.You get quite of lot of precipitation.That is water condenses when it warms up.It will take a lot of rain for your pond to overflow.

I've installed a few outdoor ponds, and I've never seen anything other than the pre-fabricated mold types overflow, and only rarely at that. Just make sure you keep the water level about 6 inches below the edge of the mold/liner, and use rocks, plants, or whatever else appeals to you to cover the unsightly black plastic. Shouldn't have any problems with overflowing then. ^_^

For the most part it will overflow and yes you will have to drain it just like a swimming pool when it rains too much.

sometimes it will overflow, especially after torrential downpours
no worry, this is normal, won't hurt anything, after the sun comes out excess water will evaporate or you can drain it if you want to

whell you dont fill it to the top but about 1 inch or 2 from the top to avoid that problem. it would take quite a bit of rain before it oveflows, but the sun will eventually evaporate the water bringing the water level back to normal

Yes, it can overflow.

Location is critical for placing an outdoor pond. It's very important that rainwater and yard-watering runoff does not flow into your pond. This runoff can contain pesticides, herbicides, and toxins that can hurt your pond. Backwash from a neighbor's yard killed all my fish last year. The backwash had herbicide in it.

Look at the way rainwater flows in the place you're planning to put the pond. Make sure water won't run into it and make sure there won't be any backwash into it. Most outdoor pond liners have a slight "lip" that will help prevent this.

Important things about a pond:

1. Ponds need about 6 hours of sun daily. This helps fight algae.
2. Ponds need plants. Water hyacinths, water lilies. This helps fight algae and helps shade the water.
3. Ponds with fish have less algae.
4. Ponds with aeration (bubbler, sprayer, waterfalls) have less algae.
5. Ponds maintained with enzymes (such as beneficial bacteria tablets) have less sludge and enzyme. You can buy beneficial bacteria at home improvement stores like Lowe's.

As you see, algae and sludge are your enemies. Most ponds turn green quickly without most of the above steps.

A pond is a small ecosystem and must be balanced. It sounds daunting and complicated at first, but it really isn't. My own pond has lots of algae on the sides for the fish to eat, but the water is clear.