The pH of the creek is slightly acidic and the concentration of water hardness is 12 milligrams per liter.

Metals such as magnesium, calcium, chromium, manganese, iron, nickel, copper, zinc, cadmium, aluminum, lead, and arsenic have been observed in the creek's waters in various amounts.

Additionally, the creek has a high level of macroinvertebrate diversity, including a number of pollution-intolerant taxa.

It flows southwest for approximately a mile before turning south-southwest and then west-southwest, exiting the valley.

At this point, the creek receives an unnamed tributary from the left and flows in a west-northwesterly direction for a few tenths of a mile.

It then flows in a west-southwesterly direction for a few tenths of a mile and receives an unnamed tributary from the right as it passes through Forest City Station.

[1] Clarks Creek joins the Lackawanna River 34.8 miles (56.0 km) upriver of its mouth.

[4] The concentration of nitrogen from ammonia in the middle reaches of Clarks Creek was measured to be less than 0.02 milligrams per liter.

[4] The concentration of magnesium in Clarks Creek in its middle reaches was found to be 0.89 milligrams per liter on April 24, 2002.

The lowest points in the watershed, near the creek's mouth, have an elevation of approximately 1,420 feet (430 m) above sea level.

The highest points, in the northeastern part of the watershed, have an elevation of approximately 2,240 feet (680 m) above sea level.

[4] The creek's channel was once modified, causing it to skirt a hill to the south and reach its confluence with the Lackawanna River a short distance downstream of its former mouth.

However, patches of fill, Wisconsinan Ice-Contact Stratified Drift, and surface mining land occur near the creek's mouth.

Surface mining land consists of linear pits and piles of waste rock.

Additionally, some areas of bedrock consisting of sandstone and shale occur in the surficial geology near the creek, but not right alongside it.

[4] Clarks Creek is entirely within the United States Geological Survey quadrangle of Forest City.

[3] The Pennsylvania Fish and Boat Commission surveyed Clarks Creek in 1997, from its mouth to a point 560 metres (1,840 ft) upstream.

[9] The drainage basin of Clarks Creek is designated as Exceptional Value waters and a Migratory Fishery.

In a 217-individual subsample from the creek's middle reaches, 79 were mayflies, 51 were true flies, 37 were stoneflies, and 28 were caddisflies.

The modified EPT (Ephemeroptera, Plecoptera, and Trichoptera) Index value of the creek is 15 in both its lower and middle reaches.