when it rains alot

One time a Dam man went to drink the Dam water. He was all out of Dam water so he went and got his Dam bucket to fill it up with Dam water from the Dam well. His Dam well was empty, so he went to another Dam man to get Dam water. He asked the Dam man," Can I have some Dam water, Please?" The Dam man Replied, "Get your own Dam water!"

The volume of water going over the dam and

the distance the water falls

The beavers had built an impressive dam over the river, effectively blocking most water traffic.

Yes, they can. If a dam is placed across the river, falling water over the dam can drive turbines which produce electricity.