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Streams 101

A stream is a complex living system where the physical characteristics of the stream bed and the valley it’s contained within—including its shape, elevation drop, and soil types—interact with dissolved nutrients and organic matter in the water to create an environment rich with life.

Too often, streams are treated as drainage channels, with no other purpose than to move storm runoff (and all its associated pollutants) downstream as efficiently as possible.

Understanding and respecting steams as dynamic ecosystems will go a long way towards protecting water quality and stream health. In fact, streams do a better job of protecting us and our property during flood events when they’re healthy.

Components of a Healthy Stream Include:

  • Cool, clear, oxygen-rich water that is free of pollutants and excess algae.
  • Gravel and cobble, without too much sand and silt, for aquatic insects and fish spawning.
  • Presence of both slow pools to provide cover and refuge, and riffles (fast water running over shallow rocks) to support aquatic insects, fish spawning and feeding.
  • Adequate amounts of water flowing in the stream during summer.
  • Fallen logs, branches and other natural debris to provide habitat and cover for aquatic and riparian species.
  • Abundant, native riparian (streamside) vegetation to stabilize banks and provide shade, food and shelter for wildlife.

The Riparian Zone

Riparian areas represent less than 1% of Utah land, yet are the most important and heavily used wildlife habitat in the region. 82% of all bird species in the Intermountain West are dependent on riparian habitat.

Healthy riparian areas are vital to the health of stream ecosystems and the entire watershed as well. Many of the threats to our urban streams are directly related to physical changes to these areas and loss of vegetation. Naturally occurring riparian plants in Salt Lake County include grasses, sedges, willows, dogwood, wild rose, sumac, birch, maple, cottonwood, and much more.

Riparian zones provide the following important benefits:

  • Extensive root systems of riparian shrubs and trees stabilize streambank soils.
  • Floodplains allow a stream system to store and absorb floodwaters, dissipating their destructive energy. High waters overflow out of the channel onto the floodplain.
  • Vegetation slows down instream flows and helps to dissipate floodwater energy.

  • Plants slow runoff as it flows over the land, allowing pollutants to drop out before entering the stream.
  • Root systems of riparian plants filter pollutants.

  • Streams provide much needed wildlife corridors, especially in urban areas where habitat is highly fragmented.
  • Multi-story layers of vegetation (trees, shrubs, ground layer) provide habitat and shelter for a diverse array of species. This structurally complex arrangement is often unique to stream corridors in arid lands.
  • Tree shade helps to cool stream waters, which is critical for many aquatic species. Roots create stable overhanging banks, providing places for fish to hide and rest.
Floodplain Riparian zone Flood prone elevation Bankfull elevation Aquatic zone Floodplain Riparian zone Uplands

Elevation Map

Elevation map of riparian zone, aquatic zone, floodplains, and uplands.

We All Live in a Watershed

A water what? A watershed, or drainage basin, is the area of land that drains to a particular body of water, such as a stream, river, lake or ocean. The topography of the landscape determines where the water flows with surrounding ridgelines defining the boundaries of the basin.

Larger watersheds contain many smaller watersheds. For instance, each mountain stream that flows into Big Cottonwood Creek has its own watershed, and when combined these streams are all part of the larger basin that drains to Big Cottonwood Creek. In turn, the watersheds for Mill Creek, Big Cottonwood Creek, Rose Creek, etc. are all part of the greater Jordan River Watershed. At an even larger scale, the Jordan River Watershed is part of the Great Salt Lake Basin. The Great Salt Lake is a closed basin; the lake is the lowest point in the landscape and does not have an outlet. Many regional scale watersheds in the United States will ultimately drain to the ocean.

When it comes to protecting nature and controlling pollution, it’s beneficial to think in terms of watershed-scale planning. That’s because everything that happens within a watershed may ultimately affect the water quality of the stream, river or lake at the bottom of the basin. Pollutants on the ground are picked up by storm runoff and make their way into our streams and rivers.

Runoff in developed areas, where there are many more impervious (non-porous) surfaces like rooftops and pavement, will flow faster and pick up more pollutants as compared with precipitation that falls on undeveloped land. As urbanization continues, more impervious surfaces lead to ever growing volumes of runoff dumping into our streams and rivers. This results in a higher probability of erosion, degraded water quality, impacts on fish and wildlife, flooding, and property damage.

Watersheds often cross city, county, and state boundaries, posing challenges to watershed planning and protection. Stream restoration, educational outreach, use of best management practices (BMPs), and collaboration across watershed boundaries are tools used to protect watersheds.

Bottom line—no matter where you live, you live in a watershed!

1+ Sub-baso Valley

Tributary Creek

A tributary creek which joins a small stream, which is tributary of a larger river, is thus part of a series of successively smaller area but higher elevation “nested” basins. Arrows indicate the direction of waterflow into the basin.