Locust Creek begins in a pond in East Cameron Township. It flows east-northeast through a deep, broad valley for several tenths of a mile before entering Mount Carmel Township. The creek flows east-northeast for more than a mile before receiving an unnamed tributary from the and abruptly turning north-northwest. For the next several tenths of a mile, it flows alongside Pennsylvania Route 54 through a water gap. The stream then leaves the water gap, crosses Pennsylvania Route 901, and turns west. A few tenths of a mile further downstream, it reaches its confluence with Shamokin Creek. Locust Creek joins Shamokin Creek upstream of its mouth.
Tributaries
Locust Creek has no named tributaries, but it has one unnamed tributary. This tributary is known as UNT #18656 and of it is an impaired waterbody.
Hydrology
Locust Creek has poor water quality. The entire length of Locust Creek is designated as an impaired waterbody. The cause of the impairment is metals and the source is abandoned mine drainage. The acid mine drainage impacts to the creek are severe. Locust Creek is an intermittent stream, with some ephemeral reaches. It is fed by several mine discharges known collectively as the Locust Gap Mine discharges. The creek also leaks water into underground mines. In three measurements between 1997 and 2000, the discharge of the stream ranged from. In March 2000, the water temperature of the stream was measured to be, while the specific conductance was 299 micro-siemens per centimeter at. As of 1972, the pH of Locust Creek averages 3.6, but can be as low as 3.2. The concentration of acidity averaged, but could be as high as. The average iron concentration was on average, but could be as high as. The concentration of dissolved solids was high enough to cause sanitation problems. However, in March 2000, the concentration of suspended solids was less than. The turbidity of the stream was 1.0 Nephelometric Turbidity Units. The water hardness was. In March 2000, the concentrations of recoverable sodium and potassium in Locust Creek were. The concentrations of recoverable magnesium and calcium were. The concentrations of recoverable manganese and iron were, while the recoverable aluminum concentration was. In March 2000, the concentration of dissolved oxygen in Locust Creek was, but no carbon dioxide was observed. The nitrogen concentration was, while the phosphorus concentration was. The chloride and sulfate concentrations were. The ammonia concentration was less than and the nitrate concentration was less than.
Geography, geology, and watershed
The elevation near the mouth of Locust Creek is above sea level. The elevation of the stream's source is between above sea level. There is a thick coating of iron precipitate on Locust Creek. Locust Gap is in the vicinity of the creek. The watershed is fairly flat, with many slopes being 25 percent or less. The creek cuts a water gap through Locust Mountain, revealing an anticlinal. The watershed of Locust Creek has an area of. The stream is entirely within the United States Geological Survey quadrangle of Mount Carmel. Much of the watershed of Locust Creek is occupied by refuse areas. However, the creek's watershed is mostly on forested land. Explo-Tech Inc. has a permit to discharge some form of waste into Locust Creek.
History and recreation
Locust Creek was entered into the Geographic Names Information System on August 2, 1979. Its identifier in the Geographic NamesInformation System is 1179768. A bridge carrying Pennsylvania Route 901 crosses Locust Creek. This bridge has been slated for preservation as part of the state of Pennsylvania's "Decade of Investment". There are some trails in the vicinity of the creek's headwaters.
Biology
The drainage basin of Locust Creek is designated as a Coldwater Fishery and a Migratory Fishery. Species such as Juncus biflorus and Platanthera ciliaris could potentially inhabit the area near the headwaters of Locust Creek.
