Build Your Own Dam

Beaver away with any supplies you can find to create and test your own beaver dam at home (warning: could get messy!)

WARNING: adults please note the use of scissors should be supervised appropriately according to age.

What you will need

Ideally do this outside where water escape doesn’t matter…

  • Water-tight tray for building in, or use a length of tin foil to create a river – stretch out about 1m of tin foil, fold up the sides to about 10cm each leaving a gap in between, then fold up each end so it can contain water.
  • Small bucket or jug of water
  • Selection of materials for dam building. Natural and recyclable is best, but it could also be a good use of old bits and bobs lying around the home; 
    • Paper scraps
    • Cardboard
    • String
    • Wood 
    • Plastic scraps
    • Small stones
    • Moss or grass
    • Basically anything that can be added to pile and wedged together
    • Modelling clay (playdoh/plasticine/clay…) – this is the key to a good dam, acting like mud in real beaver dams
  • A towel or old cloth to mop up, particularly if you’re inside..
  • Optional: some lego/playmobil people to plant downstream


The overall aim here is to have fun experimenting with the science of engineering & water movement, as well as learning what beavers achieve while their beavering away.

Before you start, have a think about what you think the best dam construction materials might be and why? How much water do you think your dam could hold?

Step-by-Step Instructions

Step 1

Head outside or do this in a kitchen/bathroom where water spillage is ok! Then set up your foil river or plastic tray, with a slight slope to it.

Step 2

Pour water slowly in from one end (‘up stream’) and watch it flow down the slope and collect in the other end. 

Step 3

Build your dam across the middle of your ‘river’ or tray; use your creative engineering skills to think how best you can stick it all together and remember, beavers use the natural materials all around them. 

Step 4 (optional)

To make things more realistic, add a few lego or playpeople characters stood on the lower slope of your river/tray, to represent people and things downstream of the dam.

Step 5

Pour water slowly in at the top of your slope, above the dam, and time how long it takes to fill up the other end. Does it get through at all? Can your dam hold water long enough to float a small object in it? Could you add anything else to allow it to filter slowly through? 

Step 6

Can you tweak your design or build your dam differently so that it holds water for longer or withstands the flow of your river better? Time how long it takes for all the water to reach the other side, then add different materials and time it again.

Now have a think about this:

  1. What changes could you make to hold the water back further?
  2. How much effort would you need to maintain a dam in the wild for the next 10 years?
  3. Chat with someone in your family about what our real rivers might look like with beaver dams here and there upstream of flooded towns.

Share your creations!..

As always we would LOVE to see how you get on and share your experiences with the world, so tag us @beavertrust and have fun building…