What is the best material to use and manner to build flood irrigation berms?
As a general rule berms should be three times as wide as they are tall for them to hold up. A heavy clay soil is usually a great material for the berms. Planting some grass on them helps to prevent erosion as the roots get set into the berms they provide stability. Keep the berms free of leaves and other debris that will cause erosion or failure points, thus leaks!