RGeology 102 935

Development of Stream and Landscapes

Streams surround us everyday of our lives, no matter where you live. They are one of the most important natural features of the Earth as well. The first civilizations were based around rivers in the west and recently rivers have been the beginnings of new cities in new countries, such as our own. Streams may be one of the most amazing surface features on the Earth. Their dynamics and specializations make them amazing. All streams start from a youthful stage where they down-cut towards base level and grow from erosion. All streams on earth do have special parts to them as well as special characteristics.

All streams have energy, but it is not always the same for every stream. Some may have a very high energy while others may barely have any. Stream energy depends upon a few factors. These factors being:

Gradient: the slope of the channel in feet or inches per mile; also called velocity.Size, shape, and condition of the channel in relation to turbulence: for example is there is a high amount of rocks in the channel, the turbulence will be increased and the energy will be decreased.Discharge: the volume of water the flows past a point in any given amount of time.Load carrying ability: graded streams are able to carry their load without trouble which leads to a fairly smooth profile and clear water whereas a non-graded steam doesn’t have the ability to carry its load which leads to generally muddy water with many rocks in the bed.

Like most other features on the Earth, streams must go through a series of stages and evolution however; it is not only the stream that goes through these stages of development but the land around the stream as well. Landscape development and Stream development parallel each other. The three stages of land and stream development and evolution are youthful, mature, and old age.

Youthful Streams and Landscapes

Youthful streams and landscapes are usually the easiest to identify. Here is a list of common characteristics of a youthful landscape.

Usually contain youthful or intermittent streams Have no floodplains Are located within the headwaters area Are usually made up of 20-80% un-dissected upland or flat land.

Here is a list of common characteristics of a youthful stream. Have a high gradient Have a high velocity Have a low volume Usually have straight channels Stream fills most of the V-shaped valley Streams are mostly graded; clear with a generally smooth profile There can be many areas of turbulence such as small waterfalls and rapids Usually the youthful stream are down cutting toward base level The streams begin at their headwaters with gullies and rills

An example of a youthful stream. This stream is full of energy; notice the water fall and abundance of rocks within the channel.

Mature Streams and Landscapes

Mature streams and landscapes are quite different from both the youthful and the old age stages. They do not have the youthful, just created look as the youthful streams and landscapes do. Some common characteristics of a mature landscape include:

Most land is in a slope Rolling topography/ rounded hilltops Only 5% or less of the land is un-dissected There are usually small to moderate floodplains Mature streams.

Some common characteristics for identifying mature streams are: Reduced gradient Closer to base level due to the reduced gradient Moderate velocity Moderate volume Moderately wide floodplain (1-3miles) Energy shifts from down-cutting to more lateral erosion Well developed meanders; natural curves in a stream due to shifting currents Only a few oxbow lakes, natural levees, and sand/gravel bars. Usually have a short life span

Old Age Streams and Landscapes

Old age streams and landscapes have been around for many years, as their names imply. Old age landscapes usually exhibit these characteristics:

House old age streams Are generally flat plains, at or near base level (sea level) Are common to have monadnocks: resistant hills that seem to stick out of the landscape.

Old Age Streams are some of the oldest bodies of water on the Earth. Some common features of old age streams include:

Low or little gradient Non graded High volume but a low velocity Low bed load, mostly sand and silt Very wide floodplain, often 20 miles or more Abundant and intensive meanders Many oxbow lakes and scars Little farmland due to excess moisture in the soils Back swamps: compacted areas of land where water stands Yazoo streams: streams that parallel an old stream but cannot enter it due to the natural levee Extensive alluvial deposits Abundance of islands and mudbars Has tributary streams

Common examples of old age streams include the Mississippi and Ohio Rivers.

Example of a mature landscape in Pennsylvania. Notice the rather flat land in

comparison to a youthful landscape.

An example of monadnocks in Eastern Kentucky

Meanders tend to be intense in old age streams. Notice how within one meander there are

others. There is also and abundance of oxbow lakes.

This illustration shows the development of an oxbow

lake as well as an oxbow scar (meander scar).