Earth Explorers

The Tennessee River from Signal Point The high mountains and deep valleys of the Appalachain mountains are exposed to all kinds of weather, from dry heat to snow and rain. All precipitation, snow, rain, or ice, will either seep into the ground or run off downhill. The total area of land where precipitation runs off and collects into a particular stream or waterbody is called a watershed. Every piece of land above sea level is part of a watershed.

View of Chattanooga from Point Park The watershed for the Tennessee River is approximately 40,000 square miles, draining parts of Virginia, North Carolina, Kentucky, Tennessee, Alabama, Georgia and Mississippi. Due to the large watershed and the temperate climate in the region, abundant water flows in the Tennessee River. Approximately 11 million gallons a day flow past Chattanooga. The Tennessee River forms north of Knoxville at the point where the Holston and French Broad rivers meet. It flows 650 miles through Tennessee, Alabama, the edge of Mississippi and through Kentucky into the Ohio River. It is the largest tributary of the Ohio River.

Profile of Tennessee River showing elevations of dams. Nine dams have been constructed along the Tennessee River to control flooding and to provide adequate river transportation. At many dams, hydroelectric plants have been located to provide electricity for millions of people in the Tennessee Valley.

When running water flows, it has a goal - to reach a point of base level where it no longer flows downhill. For all systems around the world, base level is sea level. All water rushes to rejoin the sea. The building of dams creates a new base level for water - the base of the dam which is stopping the water. The water pools at the dam forming a man-made lake. In the springtime, snowmelt from the mountains or intense rainfall events can cause damaging floods. Dams hold some of this floodwater and thus quiet the natural system.

Tennessee River North Chickamauga Creek. Notice the large boulders. Have you ever noticed the large rocks and boulders in the streams around Chattanooga? Yet when you travel to other areas of the country, even to western Tennessee, the large rocks and boulders are not in the streams in those areas? Why not?

The first stage of the erosional process is the breaking down of solid rock. In this area of the country, water is the primary erosional force. Tiny droplets of water work their way into solid rock sometimes dissolving the rock and at other times, freezing to ice inside the rock. When water freezes, it expands in size, causing the rocks to form first tiny fractures and later larger cracks. Eventually, over time, sometimes centuries, a large expanse of solid rock will break apart into boulders. The boulders go through the same erosional process and break down into large rocks. Given enough time, a large boulder will eventually break down into sand and individual mineral crystals. So next time you are at a beach wiggling your toes in the sand, think about how centuries ago, the sand used to be part of the mountains.

Bridge over North Chickamauga Creek at normal flow. Large boulders and rocks don’t move very far downstream from where they first break off from the parent rock. Why? They weigh too much! A large boulder can only be moved by a force great enough to lift the boulder. What kind of natural force can do this? Water. Water in a large volume and moving fast enough can move very large, heavy objects great distances.

North Chickamauga Creek at flood levels.

Flash floods can be a great moving force. Flash floods occur after a large rainfall or quick snowmelt when the water does not seep into the ground but rolls over the hillsides. The water quickly collects together creating a massive destructive force which can move boulders, cars and people.

Close-up of water flowing over rocks at Shoal Creek

Stream Types:
1. Perennial - streams flowing year round
2. Intermittent - streams flowing at
different times of the year, or
seasonally,when there is enough water from rain or snowmelt.
3. Ephemeral - streams existing for short periods of time, usually during a rainy period. They have defined
channels even when dry.

Shoal Creek Healthy streams and rivers are measured with biological and physical indicators. The five major indicators include: water chemistry, habitat structure, energy dynamics, biotic interaction and hydrology (the flow regime). Monitoring streams and rivers on a regular basis can alert people if a problem develops so appropriate action can be taken.