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 Wysłany: Czw 0:45, 06 Sty 2011 Temat postu: River sediment and aquatic habitat _195 |
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Aquatic habitat and river sediment
Travel and no fine gravel supply conditions, the sandy bed coarsening may occur; in the opposite conditions, the peak of the substantial reduction may prevent the coarse sand and fine sand from Xinjiang rr 2l11 ■ 1Ir Vol 29 IU Water Science and Technology Phase 1 of total invertebrates were 80% and 21%. Viscous quality of the natural riparian disabilities, slow flow of regional and river bank protection works Chau J-section of people such as invertebrates (fire at 0.5mm) high density, about one per square meter lO3 ~ 1o4 creatures. Sandy bed rivers and the adjacent main channel habitats slow water areas, including: cattle briefly abandoned tanks and other lakes and swamps,[link widoczny dla zalogowanych], slow streams, Vice slot, floodplains were admitted pits, natural scour hole, the downstream spur local pit, steps river training works and trees such as the sinking region, great biological value of these areas, bio-breeding strong. Slow flow area is fine sand deposition in a favorable position, the question often live in densely latent class of a large number of large benthic invertebrates at the same time, they also for those who prefer a smaller than the main channel flow velocity, bed material finer fish l provide habitat. Flow of natural barriers (such as: large wooden humic material,[link widoczny dla zalogowanych], vegetation, river bed and Jiangxinzhou) and man-made barriers (such as: flip groin and human waste) to extend the river sediment, nutrients and organic particles in the presence, asked These areas are biological barriers to access to food and nutrition an important place,[link widoczny dla zalogowanych], such a region upstream of the main channel of the Mississippi River about 17%, they maintain a variety of benthic biota. Once a lot of slow flow area is filled with sludge will be converted to a land habitat, flood plain development, coupled with the stability of river flood control and regular implementation of the project will accelerate this transformation process, and, channel stability, and control project will lead to the emergence of new backwater areas, which will prevent or greatly slow down the sandy bed rivers lateral oscillation process. Studied in detail the formation of the current rate of slow flow region found that many of the major rivers in the United States slow flow blockage rate of the measured area is very striking (Table 2), while storing and stability of river channel works also reduces the large horizontal swing speed channel, resulting in the formation rate of slow flow areas decreased significantly. Missouri River levee and bank protection works and the closure of the upstream reservoir makes nearly half of the land converted into aquatic habitats habitats, some of the river with the water all round the region has been the loss of habitat, while leaving only the main biological reproduction is poor slots, along with the overall habitat diversity significantly reduced. In contrast, the stability of river training works upstream projects and the Mississippi River resulting from changes in the terrain is relatively smaller, mainly because, compared with the Missouri River, Mississippi River water level regulation is far less than the average and peak water level. Table 2 The measured major U.S. river sediment deposition rate of slow flow river sedimentation rate cm / y from 4.10 during the pit, who 1.8l965.75McHenry 1.1l964-74McHenry Lake Pepin Mississippi River and others such as Upper Great Lakes l7l964.74Eckblad Illinois River Lake Peoria man 20l90l3.85Bhowmik and DemissieTombigbee River l4 cutoff meanders l8-3l976-87Shields river bed and sand bed Gibson8 river sand or mud or sticky river bed, according to its bed of sand density and viscosity sand bed may be the case in the flow of large amplitude motion, may also be in the majority of current conditions remain stable. Sticky sand river bed are more common, but rare type of non-estuarine sand bed rivers, this is because the smaller the shear stress can start non-sticky sand. Most of the sand bed of the river is expected to actually be sandy or sandy river bed of small gravel mix,[link widoczny dla zalogowanych], this is because from the river washed into the river or sand from the wash load may be adopted by the movement of the river . More common is the adhesive clay or sandy banks of river sand mixed sandy river bed. In addition to the scope of this study beyond the outside of the estuary, the sand bed river sediment and biological relationship between the literature is very scarce. 9 suspended sediment particle size of suspended sediment particle size generally smaller than the bed of sand, for example: near the city of Green River, Utah Jensen sandy river bed, the suspended sediment by 75% of fine sediment composition. Stalnaker and others believe coarse river bed of the river flow in the base question, fine sediment deposition in the river bed, and when the flow exceeds a critical value, and from the bed of fine sediment washed from; and the different sand quality of the river bed of fine sediment in the water in the bed of sand deposition and off continuously cycle between the suspended load. As a wash load of fine sediment through the sandy river channel, the suspended sediment in the increase of fine sediment will not be 23 '~-TrmIIg1j,[link widoczny dla zalogowanych]! L
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