Hydraulic roughness is the measure of the amount of frictional resistance water experiences when passing over land and channel features.[1] One roughness coefficient is Manning's n-value.[2] Manning's n is used extensively around the world to predict the degree of roughness in channels. Flow velocity is strongly dependent on the resistance to flow.[3] An increase in this n value will cause a decrease in the velocity of water flowing across a surface.[4]
Manning's nedit
The value of Manning's n is affected by many variables. Factors like suspended load, sediment grain size, presence of bedrock or boulders in the stream channel, variations in channel width and depth, and overall sinuosity of the stream channel can all affect Manning's n value. Biological factors have the greatest overall effect on Manning's n; bank stabilization by vegetation, height of grass and brush across a floodplain, and stumps and logs creating natural dams are the main observable influences.
Biological Importanceedit
Recent studies have found a relationship between hydraulic roughness and salmon spawning habitat; “bed-surface grain size is responsive to hydraulic roughness caused by bank irregularities, bars, and wood debris… We find that wood debris plays an important role at our study sites, not only providing hydraulic roughness but also influencing pool spacing, frequency of textural patches, and the amplitude and wavelength of bank and bar topography and their consequent roughness. Channels with progressively greater hydraulic roughness have systematically finer bed surfaces, presumably due to reduced bed shear stress, resulting in lower channel competence and diminished bed load transport capacity, both of which promote textural fining”. Textural fining of stream beds can affect more than just salmon spawning habitats, “bar and wood roughness create a greater variety of textural patches, offering a range of aquatic habitats that may promote biologic diversity or be of use to specific animals at different life stages.”[5]
Referencesedit
^Vieux, B.E. (2004). Distributed Hydrologic Modeling Using GIS. Springer. p. 14. ISBN9781402024597. Retrieved 2015-07-24.
^"Verified Roughness Characteristics of Natural Channels". wwwrcamnl.wr.usgs.gov. Retrieved 2015-07-24.
^Fard, R., Heidarnejad, M., & Zohrabi, N. (2013). Study Factors Influencing the Hydraulic Roughness Coefficient of the Karun River (Iran). International Journal of Farming and Allied Sciences, 2(22), 976-981. ISSN 2322-4134
^Kondolf, G.M.; Piégay, H. (2003). Tools in Fluvial Geomorphology. Wiley. p. 294. ISBN9780471491422. Retrieved 2015-07-24.
hydraulic, roughness, measure, amount, frictional, resistance, water, experiences, when, passing, over, land, channel, features, roughness, coefficient, manning, value, manning, used, extensively, around, world, predict, degree, roughness, channels, flow, velo. Hydraulic roughness is the measure of the amount of frictional resistance water experiences when passing over land and channel features 1 One roughness coefficient is Manning s n value 2 Manning s n is used extensively around the world to predict the degree of roughness in channels Flow velocity is strongly dependent on the resistance to flow 3 An increase in this n value will cause a decrease in the velocity of water flowing across a surface 4 Manning s n editThe value of Manning s n is affected by many variables Factors like suspended load sediment grain size presence of bedrock or boulders in the stream channel variations in channel width and depth and overall sinuosity of the stream channel can all affect Manning s n value Biological factors have the greatest overall effect on Manning s n bank stabilization by vegetation height of grass and brush across a floodplain and stumps and logs creating natural dams are the main observable influences Biological Importance editRecent studies have found a relationship between hydraulic roughness and salmon spawning habitat bed surface grain size is responsive to hydraulic roughness caused by bank irregularities bars and wood debris We find that wood debris plays an important role at our study sites not only providing hydraulic roughness but also influencing pool spacing frequency of textural patches and the amplitude and wavelength of bank and bar topography and their consequent roughness Channels with progressively greater hydraulic roughness have systematically finer bed surfaces presumably due to reduced bed shear stress resulting in lower channel competence and diminished bed load transport capacity both of which promote textural fining Textural fining of stream beds can affect more than just salmon spawning habitats bar and wood roughness create a greater variety of textural patches offering a range of aquatic habitats that may promote biologic diversity or be of use to specific animals at different life stages 5 References edit Vieux B E 2004 Distributed Hydrologic Modeling Using GIS Springer p 14 ISBN 9781402024597 Retrieved 2015 07 24 Verified Roughness Characteristics of Natural Channels wwwrcamnl wr usgs gov Retrieved 2015 07 24 Fard R Heidarnejad M amp Zohrabi N 2013 Study Factors Influencing the Hydraulic Roughness Coefficient of the Karun River Iran International Journal of Farming and Allied Sciences 2 22 976 981 ISSN 2322 4134 Kondolf G M Piegay H 2003 Tools in Fluvial Geomorphology Wiley p 294 ISBN 9780471491422 Retrieved 2015 07 24 Buffington J amp Montgomery D 1999 Effects of hydraulic roughness on surface textures of gravel bed rivers Water Resources Research 35 11 3507 3521 Retrieved December 15 2015 http citeseerx ist psu edu viewdoc download doi 10 1 1 459 6346 amp rep rep1 amp type pdf nbsp This erosion article is a stub You can help Wikipedia by expanding it vte nbsp This hydrology article is a stub You can help Wikipedia by expanding it vte Retrieved from https en wikipedia org w index php title Hydraulic roughness amp oldid 1184987670, wikipedia, wiki, book, books, library,
