National Forests in southern California contain fire prone ecosystems and significant watersheds that are susceptible to post-fire erosion. Using the 2,348 ha Kinneloa fire near Pasadena, CA and associated debris basins as a case study, we found that a long time-interval wildfire resulted in $2.5 million of sediment management and watershed rehabilitation costs for several city, county, state, and federal agencies. The wildfire suppression costs were $7 million. There was also $.26 million in lost recreation due to the closure of the area to visitors. The total cost from the Kinneloa fire was $9.721 million. A multiple regression analysis of fire interval and resulting sediment yield indicated that reducing the fire interval from the current average 22 years to a prescribed fire interval of 5 years would reduce sediment yield by 2 million cubic meters in the 86.2 square kilometer watershed adjacent to and including the Angeles National Forest. Cost savings take the form of reduced sediment removal in debris basins reduced need for emergency infrastructure protection structures. Other savings include the lost recreation visitor days due to emergency fire closures of watershed recreation facilities. Direct cost savings to Los Angeles County Public Works in terms of reduced debris basin clean out would be $24 million. The ecological effects of a prescribed fire interval of 5 years were not included in this analysis.