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Sometimes forest fires have caused serious damage to both private and public property. They destroy many houses and cause deaths, particularly when they have reached villages which are close to the forests. It is more dangerous if a destructive fire burns away plants and trees that prevent erosion. If heavy rains occur after such a fire, landslides, ash flows, and flash floods can occur. This can result in property damage in the immediate fire area, and can affect the water quality of streams, rivers and lakes. Wind sometimes makes contributions to forest fires. In southern California, under the influence of Santa Ana winds, fires could move at tremendous speeds, up to 40 miles (60 km) in a single day, consuming up to 1,000 acres (4 km²) per hour.