The clear-cutting of forests in the 19th century adversely affected the ecology of the Larrys Creek watershed and its water quality. Polluting industries on the creek and its tributaries during that period included coal and iron mines and tanneries. As of 2006, water quality in Larrys Creek is quite good, although two small unnamed tributaries of Roaring Run do receive acid mine drainage from an abandoned coal mine. Agricultural runoff is another source of pollution. Effluent limits for Larrys Creek in Mifflin Township for the 5-day test for carbonaceous biochemical oxygen demand (CBOD5) are 25 mg/L, while fecal coliform bacteria count limits are 200 per 100 mL in May through September, and 2000 per 100 mL in October through April.