Item talk:Q77705
From geokb
{
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"name": "Level II scour analysis for brigde 5 (STOCTH00360005) on Town Highway 36, crossing Stony Brook, Stockridge, Vermont",
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"value": "ofr98XXX",
"url": "https://pubs.usgs.gov/publication/ofr98XXX"
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"value": 70100312
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"propertyID": "DOI",
"value": "10.3133/ofr98XXX",
"url": "https://doi.org/10.3133/ofr98XXX"
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"inLanguage": "en",
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"datePublished": "1998",
"dateModified": "2014-04-10",
"abstract": "This report provides the results of a detailed Level II analysis of scour potential at structure \nSTOCTH00360005 on Town Highway 36 crossing Stony Brook, Stockbridge, Vermont \n(figures 1\u20138). A Level II study is a basic engineering analysis of the site, including a \nquantitative analysis of stream stability and scour (U.S. Department of Transportation, \n1993). Results of a Level I scour investigation also are included in appendix E of this report. \nA Level I investigation provides a qualitative geomorphic characterization of the study site. \nInformation on the bridge, gleaned from Vermont Agency of Transportation (VTAOT) \nfiles, was compiled prior to conducting Level I and Level II analyses and is found in \nappendix D.\nThe site is in the Green Mountain section of the New England physiographic province in \ncentral Vermont. The 23.0-mi2\n drainage area is in a predominantly rural and forested basin. \nIn the vicinity of the study site, the surface cover is forest on the left and right banks \ndownstream and left bank upstream, while the right bank upstream is pasture with some \nshrubs and brush. \nIn the study area, Stony Brook has an incised, sinuous channel with a slope of \napproximately 0.01 ft/ft, an average channel top width of 109 ft and an average bank height \nof 11 ft. The channel bed material is predominantly gravel with a median grain size (D50) of \n71.7 mm (0.235 ft). The geomorphic assessment at the time of the Level I site visit on April \n12, 1995, and Level II site visit on July 9, 1996, indicated that the reach was stable.\nThe Town Highway 36 crossing of Stony Brook is a 50-ft-long, one-lane bridge consisting \nof one 48-foot steel-beam span (Vermont Agency of Transportation, written \ncommunication, March 23, 1995). The opening length of the structure parallel to the bridge \nface is 46.3 ft. The bridge is supported by a vertical, concrete abutment on the left and a \nvertical, concrete abutment with wingwalls on the right. The channel is skewed \napproximately 5 degrees to the opening while the opening-skew-to-roadway is 0 degrees. \nA scour hole 2.0 ft deeper than the mean thalweg depth was observed during the Level I \nassessment along the left side of the channel at the downstream bridge face where the flow \nimpacts a bedrock outcrop. Scour protection measures at the site included type-1 stone fill \n(less than 12 inches diameter) along the right bank upstream and at the upstream and \ndownstream ends of the left abutment, type-2 stone fill (less than 36 inches diameter) at the \nupstream end of the upstream right wingwall, and type-3 stone fill (less than 48 inches \ndiameter) at the downstream end of the downstream right wingwall. Additional details \ndescribing conditions at the site are included in the Level II Summary and Appendices D \nand E.\nScour depths and recommended rock rip-rap sizes were computed using the general \nguidelines described in Hydraulic Engineering Circular 18 (Richardson and Davis, 1995) \nfor the 100- and 500-year discharges. Total scour at a highway crossing is comprised of \nthree components: 1) long-term streambed degradation; 2) contraction scour (due to \naccelerated flow caused by a reduction in flow area at a bridge) and; 3) local scour (caused \nby accelerated flow around piers and abutments). Total scour is the sum of the three \ncomponents. Equations are available to compute depths for contraction and local scour and \na summary of the results of these computations follows.\nContraction scour for all modelled flows ranged from 2.0 to 3.2 ft. The worst-case \ncontraction scour occurred at the 500-year discharge. Abutment scour ranged from 9.7 to \n22.2 ft. The worst-case abutment scour occurred at the 500-year discharge. Additional \ninformation on scour depths and depths to armoring are included in the section titled \u201cScour \nResults\u201d. Scoured-streambed elevations, based on the calculated scour depths, are presented \nin tables 1 and 2. A cross-section of the scour computed at the bridge is presented in figure \n8. Scour depths were calculated assuming an infinite depth of erosive material and a \nhomogeneous particle-size distribution. \nIt is generally accepted that the Froehlich equation (abutment scour) gives \u201cexcessively \nconservative estimates of scour depths\u201d (Richardson and Davis, 1995, p. 47). Usually, \ncomputed scour depths are evaluated in combination with other information including (but \nnot limited to) historical performance during flood events, the geomorphic stability \nassessment, existing scour protection measures, and the results of the hydraulic analyses. \nTherefore, scour depths adopted by VTAOT may differ from the computed values \ndocumented herein.",
"description": "iv, 48 p.",
"publisher": {
"@type": "Organization",
"name": "U.S. Geological Survey"
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"author": [
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"@type": "Person",
"name": "Striker, Lora K.",
"givenName": "Lora K.",
"familyName": "Striker"
},
{
"@type": "Person",
"name": "Weber, Matthew A.",
"givenName": "Matthew A.",
"familyName": "Weber"
}
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"name": "United States",
"url": "https://geonames.org/4074035"
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"additionalType": "state",
"name": "Vermont"
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