LOS ANGELES — Southern California’s huge wildfire has turned nearly a quarter of the 1,000-square-mile Angeles National Forest into a moonscape of barren mountains looming above thousands of homes that now face the threat of flash floods and mudslides.

Experts are already evaluating the extent of risk to lives and property as well as the impacts of the wildfire on a forest ecosystem that in some areas may not have burned in at least a century.

Sprawled across the San Gabriel Mountains, the Angeles is both a playground for millions in greater Los Angeles and a true wilderness ranging from arid desert to alpine forests and peaks topping 10,000 feet. Skiers dare its steeps in winter and bears wander out of its chaparral cloak in summer for dips in suburban pools.

The chief concern is the impact the 246-square-mile Station Fire is having on the watershed. Countless canyons, ravines and gullies funnel watercourses toward communities at the forest’s edge.

The Los Angeles County Department of Public Works maintains a legendary flood-control system including 14 major dams, 500 miles of open storm channel and a nearly 3,000-mile network of underground storm drains capable of carrying storm water and debris through the metropolitan region to the ocean.

The system also includes basins — 30 to 40 in the area impacted by the fire — that intercept debris-laden flows from the canyons and trap mud and vegetation before the water continues on.

“Our concerns are that we will have a larger quantity of debris than normal being captured by our flood control system and, primarily, that individual property owners may be impacted by mudslides or mudflows to their properties,” said Mark Pestrella, public works deputy director.