In this FACTivity, you will build an insloping road to test your own model of erosion. Materials: Two large cardboard boxes with lid flaps removed (around 30 inches square and at least 12 inches high) Plastic (to line the boxes) Soil (to fill the boxes) Plastic straws Grass plugs or other small pieces of vegetation (with soil and roots attached) Watering can or hose and source of water Topics: Engineering and Forest Products, Water, Erosion, Hands-on, Indoor Activity, Modeling, Outdoor Activity, Rainfall.