Heavy rain can produce flash floods, mudslides & debris flows over burned areas from wildfires. Water repellent soils are formed when organic material such as trees, scrubs, plants and litter burn at high intensity (high temperatures), causing water repellent compounds to become vaporized which then condense on cooler soil layers below the surface, which prevents the soil from absorbing water after a fire. During heavy rains, water cannot penetrate water repellent soil layers, so it runs off like pavement which causes dangerous flash flooding, debris flows and mudslides.
