The dam and its flood control basin/reservoir are in the San Gabriel Mountains and within the Angeles National Forest.

As a flood control facility the San Dimas Reservoir is dry for most of the year, only storing water after significant winter storms.

The dam diverts floodwater to Puddingstone Reservoir, protecting the area in and around San Dimas.

As a flood control facility, the San Dimas Reservoir is dry for most of the year, only storing water after significant winter storms.

The dam's main purposes are for irrigation, flood control, and water supply.