User:Pejames21/Alluvial river

Areas that are italicized are pulled directly from the original article to see how to fit my addition in.

Areas that are bolded are my additions.

Alluvial river
''An alluvial river is one in which the bed and banks are made up of mobile sediment and/or soil. Alluvial rivers are self-formed, meaning that their channels are shaped by the magnitude and frequency of the floods that they experience, and the ability of these floods to erode, deposit, and transport sediment. For this reason, alluvial rivers can assume a number of forms based on the properties of their banks; the flows they experience; the local riparian ecology; and the amount, size, and type of sediment that they carry.''

'''At a smaller spatial scale and shorter time scale, the patterns of water movement, from events such as seasonal flooding, create different patches of soils that range from aerobic to anaerobic and have differing nutrients and decomposition rates and dynamics. When looking at larger spatial scales, the topographic features have been created by glacial events, such as glaciation and deglaciation, changes in sea-levels, tectonic movements, and other events that occur over longer time scales. These short and long-term scales together determine the patterns and characteristics of alluvial rivers. These rivers also consist of certain topographic features that include hillslopes at the formation of the valley's sides, terraces, remains of old floodplains at higher elevations than the floodplain that is currently active, levees that are natural, meander scrolls, natural drainage channels, and floodplains that are temporary, as well as permanent. '''

Flooding
Flooding is an important component that shapes channel morphology in alluvial river systems. Seasonal flooding also enhances productivity and connectivity of the floodplain. ''Large floods that exceed the 10 to 20 year recurrence interval form and maintain main channels as well as avulse and form side channels, wetlands, and oxbow lakes. Floodplain inundation occurs on average every 1–2 years at flows above bankfull stage and moderates flood severity and channel scour and helps to cycle nutrients between the river and surrounding landscape. Flooding is important to aquatic and riparian habitat complexity because it forms a diversity of habitat features that vary in their ecosystem function.''

Dams and diversions
Dams and diversions alter the natural hydrologic regime of rivers, both upstream and downstream '', with widespread effects that alter the watershed ecosystem. Since alluvial river morphology and fluvial ecosystem processes are largely shaped by the complex interplay of hydrograph components such as the magnitude, frequency, duration, timing, and rate of change of flow, any change in one of these components can be associated with a tangible alteration of the ecosystem. Dams are often associated with reduced wet season flood magnitudes and altered (oftentimes reduced) dry season baseflow. This can negatively affect aquatic organisms that are specifically evolved to natural flow conditions. By altering the natural hydrograph components, particularly reducing flow magnitudes, dams and other diversions reduce the river's ability to mobilize sediment, resulting in sediment-choked channels. Conversely, dams are a physical barrier to the naturally continuous movement of sediment from headwaters to the river mouth, and can create sediment deficient conditions and incision directly downstream.''

'''Understanding the natural attributes of alluvial rivers is necessary when restoring their function on small-scale levels below dams. Though the function of the rivers may never be fully restored, it is possible to recreate and preserve their integrity with proper planning and consideration of their necessary attributes. Restoration efforts should focus on restoring the connectivity between the main channel and other floodplain bodies that were lost due to dam creation and flow regulation. The preservation and reconstruction of these alluvial river habitats is necessary in maintaining and sustaining the ecological integrity of river-floodplain ecosystems. '''