Alluvial river
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.
[2] Natural alluvial channels have a variety of morphological patterns, but can be generally described as straight, meandering, braided, or anastomosing.
[3] Irregularities in the deposition and erosion of sediments leads to the formation of alternate bars that are on opposite sides of the channel in succession.
[3] Meandering channels are widespread in current times, but no geomorphic evidence of their existence before the evolution of land plants has been found.
[3] Past climate during the Quaternary has been linked to the aggradation and incision of floodplains, leaving step-like terrace features behind.
[3] Uplift as well as sea level retreat can also cause terraces to form as the river cuts into its underlying bed and preserves sediment in its floodplain.
[3] Natural hydrograph components such as storm events (floods), baseflows, snowmelt peaks, and recession limbs, are the river-specific catalysts that shape alluvial river ecosystems and provide for important geomorphic and ecological processes.
[4] 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.
[4] Riparian habitats are especially dynamic in alluvial river ecosystems due to the constantly changing fluvial environment.
[4] In general, young riparian vegetation and pioneer species will establish in areas that are subjected to active channel processes such as at point bars, where coarser sediments such as gravels and cobbles are present but are seasonally mobilized.
[4] Mature riparian vegetation can establish farther upslope where finer sediments such as sands and silts dominate and disturbance from active river processes are less frequent.
[4] Aquatic habitats in alluvial rivers are sculpted by the complex interplay between sediment, flow, vegetation, and woody debris.
Many species also depend on low energy backwater areas for feeding and important life cycle stages.
[5][6] 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.
[7] 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.
[2] The preservation and reconstruction of these alluvial river habitats is necessary in maintaining and sustaining the ecological integrity of river-floodplain ecosystems.
