Item talk:Q226924

{

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 "url": "https://www.usgs.gov/centers/new-jersey-water-science-center/science/mannings-roughness-coefficient-new-jersey-streams",
 "headline": "Manning's Roughness Coefficient for New Jersey Streams",
 "datePublished": "January 8, 2024",
 "author": [
   {
     "@type": "Person",
     "name": "Michal Niemoczynski",
     "url": "https://www.usgs.gov/staff-profiles/michal-niemoczynski",
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       "value": "0000-0003-0880-7354"
     }
   }
 ],
 "description": [
   {
     "@type": "TextObject",
     "text": "\u200b Coon, W.F., 1998, Estimation of Roughness Coefficients for Natural Stream Channels with Vegetated Banks: U.S.\u202fGeological Survey Water-Supply Paper 241.\u200b"
   },
   {
     "@type": "TextObject",
     "text": "Using these 11 study sites as index locations, the existing\u202fmethods for roughness estimation and application to similar\u202freaches, basins, or regions\u200b will be explored. Evaluations of bed material (particle size), slope, geology, and\u202fother factors potentially including:\u202fbankfull\u202fwidths, river\u202fsinuosity, slope variability, or ratio of main channel to\u202foverbank variability\u202fwill be examined to develop methods to estimate n."
   },
   {
     "@type": "TextObject",
     "text": "Eleven sites with pre-existing real-time\u202fstreamflow gages were\u202fselected. These sites were chosen for their representation of diverse New Jersey channel conditions, their stable stage-discharge ratings, and for having a relatively straight reach of channel that is suitable for indirect\u202fmeasurements. \u200b All sites were chosen to examine\u202fn-values within the banks, with one additional site (01391500 Saddle River at Lodi, NJ) selected to examine\u202foverbank urban flows.\u200b"
   },
   {
     "@type": "TextObject",
     "text": "Manning\u2019s Roughness\u202fCoefficient (n) is an input to\u202fthe Manning\u2019s Equation,\u202fwhich can be used for the computation of\u202fstreamflow during times it is impractical or impossible to make a measurement.\u202f\u200b Methods and regional equations for determining the value of\u202fn\u202fhave largely\u202fbeen developed in the western United States; New Jersey is comparatively\u202funstudied. New Jersey features a diverse range of stream morphologies and characteristics, which will be examined by back-computing n at 11 sites co-located with a USGS continuous discharge streamgage over the course of a 4-year study. Trends and patterns will be analyzed to develop a regional or reach-based approach for estimating\u202fn\u202fthroughout the state\u200b. This study should provide enhanced guidance for selecting roughness coefficients for future hydraulic models and studies throughout New Jersey."
   },
   {
     "@type": "TextObject",
     "text": "3450 Princeton Pike\nSuite 110\nLawrenceville, NJ 08648\nUnited States"
   },
   {
     "@type": "TextObject",
     "text": "\u200b"
   },
   {
     "@type": "TextObject",
     "text": "Over the course of this study, N\u200b will be computed for individual peaks by building slope-conveyance models for each site/reach using the surveyed cross-sections and measured inputs\u200b. These models will help analyze computed roughness coefficients and look for trends. A summary of findings for each site will be included in a SIR.\u200b\u200b"
   },
   {
     "@type": "TextObject",
     "text": "Once chosen, standard USGS crest-stage gages (CSGs) were installed to capture\u202fpeak elevations of medium to\u202fbankfull\u202fflows at each site. Three to four CSG cross-sections were established at distances of 200-500 ft. apart\u200b to fully characterize the slope-area of the site. Some sites include USGS streamgages within the cross-sections\u202fto capture peak elevations in place of an installed CSG, while the urban overbank site (01391500) had an additional CSG at\u202feach cross-section to capture over-bank flows\u200b."
   },
   {
     "@type": "TextObject",
     "text": "The channel cross-sectional geometry was surveyed at each CSG using differential levels or\u202fa total station and will be re-surveyed in the future to look for channel\u202fchange.\u200b For broad,\u202funwadeable\u202fsites, Acoustic Doppler Current Profilers (ADCPs) along with\u202fAreacomp\u202fsoftware were used for channel bathymetry and adjoined to\u202fbank\u202fsurveys.\u202f\u200bOverbank cross-sections were surveyed and appended to\u202fwithin-channel surveys at the urban overbank site.\u200b."
   },
   {
     "@type": "TextObject",
     "text": "CSG marks are recorded during routine site visits and are documented in\u202fan excel workbook for analysis. Slope is calculated between each cross-section\u200b with a peak date and associated discharge determined using\u202fstreamflow data from the corresponding USGS\u202fstreamgage\u200bs. Inputs of cross-sectional area, slope, hydraulic radius, and discharge are then used\u202fto solve for the\u202froughness coefficient\u200b."
   },
   {
     "@type": "TextObject",
     "text": "Calculated\u202fvalues and methods to estimate along a studied\u202freach will be provided: either through regional equations for estimating\u202fmain channel roughness coefficients, or the development of a reach-only selection guide.\u200b Both methods would likely attempt to utilize geospatial\u202fdatasets to simplify evaluation and reproducibility of results.\u202f\u200b"
   },
   {
     "@type": "TextObject",
     "text": "N-values\u202fcan be determined by several methods: Cowan\u2019s additive\u202fmethod, which uses a base\u202fn\u202f(n0) determined by the streambed\u202fmaterial and several modifiers (n1, n2, n3, n4, m) based on\u202fchannel characteristics, equations developed for mountain\u202fstreams and streams with a particular range in slope, or\u202fcomparing the channel to photos of a site that already has a\u202fcomputed\u202fn-value. This study is using peak discharge from a stable stage-discharge relationship to back-compute n, given other measured inputs."
   },
   {
     "@type": "TextObject",
     "text": "\u200b Cowan, W.L., 1956, Estimating hydraulic roughness coefficients: Agricultural Engineering, v. 37, no. 7, p. 473-475.\u200b"
   },
   {
     "@type": "TextObject",
     "text": "Preliminary results show a wide range of values somewhat consistent\u202fwith literature: lower roughness coefficients in a concrete-lined\u202fchannel; higher in a narrow, cobble channel. Peak elevations will be collected for three more years. Over time, we will\u202flook for trends and patterns in computed\u202fn-values.\u200b"
   },
   {
     "@type": "TextObject",
     "text": "-----"
   },
   {
     "@type": "TextObject",
     "text": "New Jersey Geological Survey, 2005, Geologic Map of New Jersey: New Jersey Department of Environmental Protection\u202fLand Use Management, 1 sheet, scale 1:1,000,000, accessed on August 16,\u202f2023\u202fat\u202fhttps://www.state.nj.us/dep/njgs/njgeol.htm"
   },
   {
     "@type": "TextObject",
     "text": "\u200b Benson, M.A., and Dalrymple, Tate, 1967, General field and office procedures for indirect discharge measurements: U.S.\u202fGeological Survey Techniques of Water-Resources Investigations, book 3, chap. Al, 30 p.\u200b"
   },
   {
     "@type": "TextObject",
     "text": "Barnes, H.H., Jr., 1967, Roughness characteristics of natural channels: U.S. Geological Survey Water-Supply Paper 1849,\u202f\u202f213 p.\u200b"
   }
 ],
 "funder": {
   "@type": "Organization",
   "name": "New Jersey Water Science Center",
   "url": "https://www.usgs.gov/centers/new-jersey-water-science-center"
 },
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     "name": "Streamflow Network"
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