User:Rwaggoner8/Stream bed

Effects on Stream bed Morphology
Streambed morphology identifies the structure of the stream’s channel bottom, which varies depending on the geographic location of the stream. There are a multitude of factors that affect the morphology of a stream, including change in vegetation, in-channel restoration structures, animals, human intervention and check dams. These factors have an effect on the morphology of the stream which has a direct effect on the aquatic ecosystem and the organisms within it. The addition of a dam on a flowing stream, for example, has a dramatic effect on the channel of the stream and surrounding banks and vegetation. This process decreases the amount of sediment transport directly downstream of the dam, narrowing the channels into a more lateral migration pattern due to the decreased amount of sediment that is eroded/deposited, with an increase of potential energy from the stream adjustments. Animals also play a key role in the bed load/sediment transport of the stream; modifying the flow of the water through foraging, hiding places, dams, and stepping on the bottom of the stream bed during migrations. Dams created by animals retain high amounts of sediment and organic matter which has effects on the morphology of the stream as well as effects on the primary/secondary producer’s production levels. The riparian vegetation, vegetation along the banks of the stream, is also affected with the creation of check or animal made dams. The results decrease the nutrient supply to the stream, and the stability of the channel/bank in regard to the loss of the riparian vegetation. With a decrease in the stability of the channels/banks, as the flow rate of the water increases, the stream’s beds/banks are either eroded away or deposited elsewhere. This in turn, changes the streambed morphology, directly impacting the aquatic ecosystem and habitats. The riparian vegetation plays an important factor in channel adjustments through inhibiting erosion and strengthening floodplain creation through increased levels of sedimentation. It alters the flow characteristics that maintain the flow velocity, and erosion/deposition patterns that add to the success of macrophyte ecology of the streams.

The removal of naturally occurring debris such as wood can also impact the morphology of the stream. It results in a change in topography of the stream as well as a change in the sediment bed placement through alterations of the bars and pools. These alterations widen the channels, causing bank erosion that removes low-level depositional areas. The stream channel directly responds by reorganizing and shifting banks to find the path of least resistance in the process of regaining equilibrium. Woody debris retains water and particulate materials, which is important in biological activity and habitat structures for invertebrates. Furthermore, the addition of woody debris impacts the stream’s morphological shape through increased levels of erosion in the middle of the stream, changing the shape from a U to a V. Changes in channel gradient are counterbalanced through changes in channel depth and width to maintain a fair stability between the frequency of the bed load transport and the intensity. Hydrologic control structures also change the stream’s hydraulic gradients and water surface profiles by steering the stream currents which changes the natural stream meanders. This human impact degrades the ecological value of the habitats and communities in the stream, and overall simplifies the geomorphological structure of the stream.