Dams are made for a variety of reasons. You may want to utilize a nearby stream to irrigate your property, create a small pool to swim in or just add a little vivacity to a languid stream. Building your dam with rocks in a creek is quite simple; however, it is a little harder to make the dam so that it won't crumble in a matter of weeks. It's all about using your materials wisely with proper placement and a proper order.
Isolate the area you wish to make your dam. This means diverting or slowing the rush of water traveling through the area you intend to work. Make a temporary dam about six feet upstream from this area by using the largest rocks you are able to move and aligning them across the creek. Fill in the cracks with branches and leaves. This will decrease the depth of the water you will have to work in and allow you to make your real dam more effective.
Start with the largest rocks you can move once again. Align these across the creek placing them directly in front of where you would like your dam to be. You are going to build your dam upward and upstream. These large rocks will act as your foundation pushing against the current of the river.
Place a layer of branches and leaves against the back layer of your large rocks. Make this layer as thick as possible making sure to fill in all the cracks left between the large rocks.
Create the back layer of your dam with small- to medium-sized rocks. Build this layer up and over your layer of branches and also your layer of large rocks. The water pressure from the stream will push these smaller rocks and branches tightly into the cracks between the larger rocks, further sealing your dam.
Remove your temporary dam slowly one rock at a time. This will ease the flow of the creek onto your new dam.