Human Influences and Natural Influences


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    Human Influences



    Road Building


    What human influences affect riparian zones?

    Road building may cause accelerated erosion, introduce oil and other pollutants to the stream, cut off subsurface water flow to the stream and threaten wildlife.

    Farming can increase erosion of stream banks if the riparian zones are cleared for more farmland. Farmland is lost where the erosion occurs and sedimentation increases downstream. More farmers now maintain the health of their riparian areas to ensure long-term sustainability of their land.

    Grazing or overgrazing of the riparian zone can cause changes in the types of vegetation and the amount of cover and forage, increase erosion, and introduce increased amounts of nutrients and fecal coliform bacteria to the stream through manure. However, if cattle are managed correctly (herded or fenced out after a short time) they can be a part of a healthy riparian zone.

    Development of riparian zones for housing or commercial development often causes removal of vegetation and alters the stream banks. These changes can increase the intensity of floods, increase the direct input of pollutants to water, and decrease wildlife.

    Logging operations today realize the importance of healthy riparian zones and rarely log them. However, logging roads continue to be built through these zones, creating the same problems that all roads do. When upland vegetation is stripped away, too much water is allowed to flow down into the stream at one time, which can lead to bank erosion, deep and narrow channels, shrunken riparian zones, and often increased loads of sediments.

    Dams reduce downstream flooding. while this serves the people who live downstream in the floodplain, it degrades riparian zones. Natural flood cycles are critical to healthy riparian zones. Floods bring essential supplies of water, nutrients and sediment. They also help to create backwater that serve as critical fish nurseries.

    Natural Influences

    Soil Type

    Water Supply



    What natural influences affect riparian zones?

    Water Supply is the major factor that regulates the growth of riparian vegetation. Flood waters transport nutrients, sediment and new seeds from upstream. Floods also strip away larger, established vegetation and allow new seedlings to establish.

    Soil type in the riparian zone influences the amount of water and nutrients available. Organic-rich soil holds water and provides abundant nutrients to plays, without releasing these nutrients to the water. We can expect to find denser vegetation in these soils than in a gravely soil with little water-holding capacity and few nutrients.

    Topography, or the shape of the land, affects the location and abundance of plants in the riparian zone.

    Climate affects the appearances of riparian zones. In the deserts  riparian zones are "green oases" in sparse, dry surroundings. Where precipitation is more abundant, like in the mountains, the upland vegetation remains relatively lush.