A wildland–urban interface refers to the zone of transition between unoccupied land and human development. Communities that are within 0.5 miles (0.80 km) of the zone may also be included. These lands and communities adjacent to and surrounded by wildlands are at risk of wildfires.
Urban development is pushing farther out of cities and into the wilderness for both primary and secondary residences. In the western states alone, 38% of the new development is taking place in the urban interface. As a result, the number of buildings and homes damaged as a result of accidental and natural forest fires has increased drastically. This has resulted in millions of dollars in damages.
One can prepare their property by performing some simple tasks, such as ensuring that the area around a building is free of any fuel (brush, high grasses, shrubs, small trees) that would allow a wildfire to reach that building, ensuring trees are trimmed in a fashion that would prevent them from falling onto the structure and road that would prevent one from evacuating.
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http://www.usfa.fema.gov/downloads/pdf/tfrs/v2i16-508.pdf