The lower reaches of the river flow through the urban areas of Scranton, which grew around its banks in the 19th century as an industrial center.

The branches, each about 12 miles (19 km) long, flow south, closely parallel to each other, and join at the Stillwater Lake reservoir in Union Dale.

It flows south-southeast for a few miles in a deep valley, crossing Pennsylvania Route 171 and passing through Forest City.

[21] After receiving the tributary Wilson Creek, the Lackawanna River continues flowing southwest alongside Pennsylvania Route 171 and soon enters Carbondale.

The river then turns south for a few miles, receiving the tributary Aylesworth Creek from the left and entering Archbald.

It then begins flowing in a southwesterly direction along the border between Olyphant and Dickson City, though it makes several sharp turns along the way.

After some distance, it receives the tributary Eddy Creek from the left and begins flowing along the border between Dickson City and Throop.

Several tenths of a mile further downstream, it receives the tributary Saint Johns Creek from the right and turns west-southwest.

[24] Between the upper Carbondale city line and Green Ridge Street, the concentration of alkalinity in various reaches of the Lackawanna River ranges from 14 to 34 milligrams per liter.

During storms, minor tributaries also wash large quantities of urban debris and coal waste into the river, degrading it further.

In Scranton, the river flows between stone and concrete retaining walls, as well as high banks of slag.

Rapids mainly occur in reaches such as Panther Bluff (in Fell Township), the Winson area (in Archbald and Jessup), near Cliff Street (in Scranton), and at the Moosic anticline (in Old Forge).

[23] The channel of the Lackawanna River is sinuous and flows through narrow, alluvial floodplains at the base of steep hills.

[27] Deposits of glacial till containing boulders, cobbles, sand, and gravel occur in the Lackawanna River watershed.

[23] The main rock formations in the Lackawanna River watershed contain sandstone and shale, with rich coal deposits.

Such land contains at least 25,000 to 30,000 acres (10,000 to 12,000 ha) of culm banks, overburden piles, silt basins, non-vegetated soil, and degraded waterways.

The early settlers were of English, Irish, Welsh, and German descent, but in the 1880s and 1920s, immigrants from southern and eastern Europe arrived.

According to Horace Hollister's History of the Lackawanna Valley, one of the destroyed graves may have belonged to Capouse, a Lenape chieftain who was visited by Count Zinzandorf, a Moravian missionary, near the river in about 1750.

These included the Erie and Wyoming Valley Railroad, which followed Roaring Brook, and the Jefferson Branch, which entered the river's watershed at Ararat Summit.

The study was carried out by the Corps of Engineers, as well as the National Park Service, the Heritage Authority, and the Lackawanna River Corridor Association.

[29] Wild trout naturally reproduce in the river from its headwaters downstream to the Lackawanna County/Luzerne County line, a distance of 35.60 miles (57.29 km).

The sections are adjacent to each other and run from the upper Carbondale city line downstream to Green Ridge Street, a distance of 17.4 miles (28.0 km).

In addition to trout, smallmouth bass, sunfish, carp, suckers, crappies, darters, and dace have been observed in the river.

There is anecdotal evidence that the river was able to function as a trout fishery in the early 1900s, though the habitat had experienced significant degradation by then.

Recovery began in the once the coal mining industry had ended in the 1960s and 1970s, and continued into the 1980s and 1990s due to the efforts of local groups and fishing clubs.

Common mammals include beavers, black bears, foxes, minks, muskrats, raccoons, and white-tailed deer.

The stretches that lack any riparian buffering are most commonly on flood control levees in Dickson City, Duryea, Mayfield, and north Scranton.

Property encroachments, coal dumps, and historic buildings in Archbald, Carbondale, Olyphant, and Scranton also detract from the river's riparian buffer.

It has Trophy Trout regulations from Blakely Corners to White Oak Run, forbidding live bait except in limited circumstances.

From Carbondale to the river's mouth, the difficulty rating is mostly 1, but there is one class-4 rapid formed by a complex ledge system at Moosic.