A model dam can be made from a few items normally already found in the kitchen. Use a Tupperware of similar plastic container, some sand, rocks and water to create a model of a structure that retains water.
To make a model dam, PBS Kids recommends placing sand in the plastic container and digging a trench in the sand that resembles the shape of a flowing river. Pick a point along the trench to build the dam. Place small rocks on it and enclose them with Popsicle sticks that stand upright. Pour a little water down the trench to start the river to see if the dam is constructed well enough to withstand the flow but still allow some water to enter the structure.
Dams are sometimes associated with levees or floodgates. Both are used to control water flow. But levees are designed to prevent water from flowing into regions. The purpose of a dam is to retain water that may also be transferred to other locations. In addition to water retention, dams can help generate electricity with the help of hydro power.
Natural causes and wildlife such as beavers help form dams. Dams can also be man-made. Man-made dams are classified by several factors, including size, height, structure and purpose.