Question: What is a tributary of the river near Tazewell, Virginia, and flows southwest for more than 300 mi through the Great Appalachian Valley, that drains a watershed area of 86.5 mi2 between Copper Ridge and Black Oak Ridge ?

Context articles: Powell Mountain
Bearwallow Creek
Beaver Creek (Tennessee)
Napeequa River
Shawangunk Ridge
Blue Ridge Mountains
Shenandoah Valley
Pochuck Mountain
Clinch River
Agua Chinon Creek

Powell Mountain (or "Powells Mountain") is a mountain ridge of the Ridge-and-valley Appalachians of the Appalachian Mountains.
 It is a long and narrow ridge, running northeast to southwest, from about Norton, Virginia to near Tazewell, Tennessee.
 It separates the Clinch River basin and the Powell River basin of Powell Valley.
 It was named for an 18th-century explorer.
Bearwallow Creek is a 4.3 mi tributary stream of Tearcoat Creek, itself a tributary of the North River, making it a part of the Potomac River and Chesapeake Bay watersheds.
 Bearwallow Creek is located in Hampshire County, West Virginia.
 It rises on Chestnut Oak Ridge, from which it flows southwest along the ridge's eastern flanks and then begins its course southeast along Bear Wallow Hollow Road (County Route 50/14) and U.S. Route 50 until its confluence with Tearcoat Creek at Pleasant Dale.
Beaver Creek is a tributary of the Clinch River in Knox County in East Tennessee.
 It drains a watershed area of 86.5 mi2 between Copper Ridge and Black Oak Ridge.
 It flows from northeast to southwest from the Gibbs High School area, through the Halls, Powell, Karns, Solway, and Hardin Valley communities, entering the Clinch downstream from Solway.
The Napeequa River is a 19 mi long river in the U.S. state of Washington on the east side of the Cascade Range.
 It rises in northwest Chelan County and flows southwest into the White River near Twin Lakes.
 The White River flows into Lake Wenatchee.
 The Napeequa River and its valley are notable for their beauty and isolation, as well as their interesting geological history.
 It flows through an isolated southeast-trending valley characterized by a broad meadows surrounded by rugged mountains.
 The Chiwawa Mountains, or Chiwawa Ridge mark the east side of the valley, separating the Napeequa and Chiwawa Rivers. To the west the White Mountains separate the Napeequa from the White River.
 Both are sub-ranges of the Cascade Range.
The Shawangunk Ridge , also known as the Shawangunk Mountains or The Gunks, is a ridge of bedrock in Ulster County, Sullivan County and Orange County in the state of New York, extending from the northernmost point of New Jersey to the Catskill Mountains.
 Shawangunk Ridge is the continuation of the long, easternmost ridge of the Appalachian Mountains; the ridge is known as Kittatinny Mountain in New Jersey, and as Blue Mountain as it continues through Pennsylvania.
 This ridge constitutes the western border of the Great Appalachian Valley.
The Blue Ridge Mountains are a physiographic province of the larger Appalachian Mountains range.
 This province consists of northern and southern physiographic regions, which divide near the Roanoke River gap.
 The mountain range is located in the eastern United States, starting at its southernmost portion in Georgia, then ending northward in Pennsylvania.
 To the west of the Blue Ridge, between it and the bulk of the Appalachians, lies the Great Appalachian Valley, bordered on the west by the Ridge and Valley province of the Appalachian range.
The Shenandoah Valley is a geographic valley and cultural region of western Virginia and the Eastern Panhandle of West Virginia in the United States.
 The valley is bounded to the east by the Blue Ridge Mountains, to the west by the eastern front of the Ridge-and-Valley Appalachians (excluding Massanutten Mountain), to the north by the Potomac River and to the south by the James River.
 The cultural region covers a larger area that includes all of the valley plus the Virginia highlands to the west, and the Roanoke Valley to the south.
 It is physiographically located within the Ridge and Valley province and is a portion of the Great Appalachian Valley.
Pochuck Mountain is a ridge in the New York-New Jersey Highlands region of the Appalachian Mountains.
 Pochuck Mountain's summit and most of its peaks lie within Vernon Township, Sussex County, New Jersey, although the south-western portion of the ridge lies within Hardyston Township, and the north-eastern tip of the ridge extends over the New York state line into Orange County.
 The ridge marks the eastern edge of the Great Appalachian Valley, and it divides the watersheds of the Wallkill River and its tributary Pochuck Creek.
 The two rivers meet at Pochuck Neck, marking the terminus of the ridge.
The Clinch River rises near Tazewell, Virginia, and flows southwest for more than 300 mi through the Great Appalachian Valley, gathering various tributaries, including the Powell River, before joining the Tennessee River in Kingston, Tennessee.
Agua Chinon Creek or Agua Chinon Wash is an urban stream in the city of Irvine, Orange County, California.
 The creek flows southwest from its headwaters in the foothills of the Santa Ana Mountains for about 8 mi to join San Diego Creek near the Verizon Amphitheatre.
 The creek drains a total watershed area of 7049 acre .