These last few weeks our 8th grade students have been working with a stream table designed to simulate and teach basic river principles, including: how river channels form and change over time and how sediment is transported and deposited within river systems.
The modeling media inside the stream table is manufactered thermoset plastic from Composition Materials Company (http://www.compomat.com/) in Milford, CT. It is sold by them as 'Stream Table Mix' and consists of various sizes and densities that do an exceptional job of modeling on sediment is transported and deposited in natural river systems. We use anywhere between 50-80 pounds of plastic within the stream table for student use.
The idea of using a large stream table came from seeing an example created by the folks at Little River Research & Design (http://www.emriver.com/).