I don't know if you guys get lots of rain in the spring, but in theory here in Texas we do. It hasn't happened yet, but the idea for this came up last year when my boys noticed all the puddles we had after two weeks of solid rain.
Of course I thought of a science experiment to go with this.
Supplies: clear glass or baby food jar for each kid (as with most things it's more effective if they can each do this), dirt, pitcher of water
1. First let your kid add dirt into the jar until it is about halfway full. You want to make sure you still have room for the water to be added in.
Then look at the jar full of dirt, look at how there are little pockets of air that are empty, where water can go into. What is going to happen when we pour the water?
If your kids are like mine there's a 50/50 chance they're going to say "You get mud!" The other chance is they tell you there will be too much water for the dirt.
That's the answer you want.
2. Slowly pour water in. As you do you'll notice that the dirt becomes saturated with the water. Once the dirt is saturated with the water the water starts to float on top of the dirt. Thus forming puddles.
So, to get to the technical answer. One way that you get puddles and flooding is if your ground has become too saturated with water for it to hold anymore water at this time.
Vocabulary word you probably introduced: saturated- to become full of something
Other posts I saw that could help with this idea:
An excellent example of flash flooding that we usually get in Texas
A great demonstration of water cycle- this was just linked up to my Science Sunday post this last week, and I thought it was so cool.
Further expansions or ideas:
Start a study of the water cycle
How does water get to your house (a great book for this is "Drip, Drip, Drop")
What happens after it rains (can transition into plants growing)