The forested land along rivers and streams is known as the “riparian zone”. Riparian comes from the Latin word ripa, which means bank. Riparian zones are areas of transition where the water and land meet and they offer many benefits to wildlife and people.
Only in the past few decades have scientists and land use specialists come to realize the value of riparian zones. Amongst the most diverse biological systems on earth, riparian zones offer many critical ecological benefits:
Overhanging vegetation and trees shade the stream channel, keeping the water nice and cool.
The vegetation along the streambank helps to hold on to the soil and prevent erosion.
These stream side wetlands also act like huge sponges absorbing and filtering the water, which reduces high flows into the stream.
Parts of a Streambank
This zone is the wetted area located below the average water mark or water level. Generally, the streambank soils next to the stream channel have the most erosion because of the constant water flow. When plants are present in this area, the plants are rooted into the soil beneath the water. Vegetation includes herbaceous species like sedges, rushes, and cattails and are found in the low energy streams or in protected, slow-moving areas of the stream.
Sedges have edges, rushes are round, and grasses have bumps all the way to the ground.
The riparian zone is the area between the average water mark and the average high water mark. The plants that are found here thrive along the banks so long as their root systems are able to access surface water and subsurface flow. When a riparian area contains healthy, native plants, there is less erosion. This zone contains predominately shrubs, willows, and other water-loving plants.
The floodplain is a relatively flat area located adjacent to a river or stream. This area can experience occasional or periodic flooding. When a river breaks its banks and floods, it leaves behind layers of sediment – rock, sand, mud, and silt. These materials gradually build up to create the floor of the floodplain. Here, the soils are a mix of sand, gravel, loam, silt, and clay. These areas are important aquifers, filtering the water drawn from them through these soil combinations. Plants found here often contain a mix of riparian and upland plants and trees – willows, dogwoods, alder, and birch trees as well as large shrubs.
A few years ago, my STEM Club spent the day inundating ourselves in Stream Ecology. Read this post to discover other activities you can use to engage your students.
The transitional zone is located between the floodplain and the upland zone. Here, the area is rarely affected by stream flow and floods only once every 50 or so years. This zone is comprised of drier upland trees and large shrubs that do not need to access the stream water or subsurface flow with their roots.
The uplands consist of land where drier vegetation can be found. The plants and trees here no longer depend upon the surface or subsurface flow of stream water for their survival. However, the taller trees in this zone do create a valuable forest canopy that helps to shade the stream.
Previously, we partnered with the USDA Forest Service to hear first hand how a forester manages a forest and to get a chance to use the real tools of the trade. Read more of our experience in my post, Field, Forest, & Stream: Forest Ecology.
Riparian Area Survey
- Tape measure
- Field notebook
- Colored pencils (optional)
- Copy the table above into your field notebook.
- Go to a nearby stream and select an area of the streambank and riparian area to study. Measure the area that you have selected.
- Complete the table checking the box for each vegetation type you see. If you are able, identify as many as possible.
- Choose a section of the length of the stream surveyed and draw the stream and riparian area from a bird’s eye view (from above).
- Once you have the basic outline of the area (stream channel, banks, riparian area), begin by marking where you see each type of trees, shrubs, ferns, etc. Use the symbols in the table above to simplify your sketch.
- Make sure to draw an arrow in the stream to show the direction of water flow.
- Based on your observations at this site, describe any human influences on the riparian area.
- What features of the riparian zone do you think are important to fish?
- Do you notice any patterns of certain vegetation types and where they are located in relation to the stream? Why do you think that is?
You will find more activities like this one in my Ecology Explorations curriculum available for purchase in my store. The Life Logic: Ecology Explorations unit that I have developed for middle school students is an easy to implement, hands-on way to learn about ecology. Students will love getting outside, collecting data, and experiencing the physical factors that influence the animal and plant communities in their local area first hand.