Build the Barrier
Friction between sandbags and the ground holds the dike in place, so remove slippery substances like leaves. If you're going to build your dike more than 3 feet (1 m) high, increase its stability by placing the bottom row of bags in a shallow trench that's about 6 inches (15 cm) deep and 2 feet (61 cm) wide. Stagger the position of bags as you stack them, as if you were laying bricks. As a rule of thumb, the width of the dike at the bottom should be two or three times the overall height.