The lake was created by damming Rock Creek in 1965 with the goal of providing flood control and reducing soil erosion.

[2][3] Lake Needwood also protects the water quality of the creek by functioning as a retention basin to trap sediment from storm-water runoff.

Other park features include a visitors center and snack bar, hiking and biking trails, playgrounds, an archery range and Needwood Golf Course.

It is made of a 65-foot (20 m) high earthen dam built on a fractured rock foundation formed at the junction of the Boulder Gneiss and Upper Pelitic Schist geological formations.

[6] At the time of construction, only the right portion of the dam bottom was treated with grout, likely predisposing the structure to generate a concentrated seepage of water from the left abutment during the 2006 Mid-Atlantic United States Flood.

[10] There have been several evacuations of downstream residents during periods of heavy rain, due to concerns about the structural integrity of the earthen dam constructed in 1965.

The evacuees lived in 500 apartments at the Rock Creek Terrace complex on Veirs Mill Road in Rockville and in 700 single family homes in that area.

In residential areas, the nutrients are generated by excessive fertilizer use and associated urban runoff, which cause harmful algal blooms (HABs) in water bodies.