SEARCH · USGS Science

Results for “Materials Performance”

Search indexed USGS publications on groundwater, aquifers, geologic maps, mineral resources and earthquakes. Explore source records by subject and place.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 325 records · Page 18Linked to original sources

USGS1997

Level II scour analysis for Bridge 22 (REDSVT01000022) on State Route 100, crossing the West Branch Deerfield River, Readsboro, Vermont

This report provides the results of a detailed Level II analysis of scour potential at structure REDSVT01000022 on State Route 100 crossing the West Branch Deerfield River, Readsboro, Vermont (figures 1–8). A Level II study is a basic engineering analysis of the site, including a quantitative analysis of stream stability and scour (U.S. Department of Transportation, 1993). Results of a Level I scour investigation also are included in Appendix E of this report. A Level I investigation provides a qualitative geomorphic characterization of the study site. Information on the bridge, gleaned from Vermont Agency of Transportation (VTAOT) files, was compiled prior to conducting Level I and Level II analyses and is found in Appendix D. The site is in the Green Mountain section of the New England physiographic province in southern Vermont. The 25.6-mi 2 drainage area is in a predominantly rural and forested basin. In the vicinity of the study site, the surface cover is forest. In the study area, the West Branch Deerfield River has an incised, straight channel with a slope of approximately 0.025 ft/ft, an average channel top width of 63 ft and an average channel depth of 10 ft. The predominant channel bed materials are cobbles and boulders with some bedrock exposure noted under the bridge. The bed material has a median grain size (D 50 ) of 141.0 mm (0.463 ft). The geomorphic assessment at the time of the Level I and Level II site visit on July 30, 1996, indicated that the reach was stable. The State Route 100 crossing of the West Branch Deerfield River is a 119-ft-long, two-lane bridge consisting of one 110-foot steel-beam span (Vermont Agency of Transportation, written communication, September 28, 1995). The bridge is supported by vertical, concrete abutments with spill-through embankments. The channel is skewed approximately 50 degrees to the opening while the opening-skew-to-roadway is 50 degrees. The scour protection measure at the site was type-3 stone fill (less than 48 inches diameter) on the spill-through embankments of each abutment and the banks upstream and downstream. Additional details describing conditions at the site are included in the Level II Summary and Appendices D and E. Scour depths and rock rip-rap sizes were computed using the general guidelines described in Hydraulic Engineering Circular 18 (Richardson and others, 1995). Total scour at a highway crossing is comprised of three components: 1) long-term streambed degradation; 2) contraction scour (due to accelerated flow caused by a reduction in flow area at a bridge) and; 3) local scour (caused by accelerated flow around piers and abutments). Total scour is the sum of the three components. Equations are available to compute depths for contraction and local scour and a summary of the results of these computations follows. There was no predicted contraction scour for any of the modelled flows. Abutment scour ranged from 4.9 to 11.6 ft. The worst-case abutment scour occurred at the right abutment for the 500-year discharge. However, historical information indicates the right abutment is in contact with bedrock at least in part. Additional information on scour depths and depths to armoring are included in the section titled “Scour Results”. Scoured-streambed elevations, based on the calculated scour depths, are presented in tables 1 and 2. A cross-section of the scour computed at the bridge is presented in figure 8. Scour depths were calculated assuming an infinite depth of erosive material and a homogeneous particle-size distribution. It is generally accepted that the Froehlich equation (abutment scour) gives “excessively conservative estimates of scour depths” (Richardson and others, 1995, p. 47). Usually, computed scour depths are evaluated in combination with other information including (but not limited to) historical performance during flood events, the geomorphic stability assessment, existing scour protection measures, and the results of the hydraulic analyses. Therefore, scour depths adopted by VTAOT may differ from the computed values documented herein.

Vermont↗

USGS1997

Level II scour analysis for Bridge 17 (POMFTH00010017) on Town Highway 1 (FAS 166) crossing Mill Brook, Pomfret, Vermont

This report provides the results of a detailed Level II analysis of scour potential at structure POMFTH00010017 on Town Highway 1 crossing Mill Brook, Pomfret, Vermont (figures 1–8). A Level II study is a basic engineering analysis of the site, including a quantitative analysis of stream stability and scour (U.S. Department of Transportation, 1993). Results of a Level I scour investigation also are included in Appendix E of this report. A Level I investigation provides a qualitative geomorphic characterization of the study site. Information on the bridge, gleaned from Vermont Agency of Transportation (VTAOT) files, was compiled prior to conducting Level I and Level II analyses and is found in Appendix D. The site is in the Green Mountain section of the New England physiographic province in central Vermont. The 8.11-mi 2 drainage area is in a predominantly rural and forested basin. In the vicinity of the study site, the surface cover is pasture. In the study area, Mill Brook has a sinuous channel with a slope of approximately 0.009 ft/ ft, an average channel top width of 30 ft and an average channel depth of 3 ft. The predominant channel bed materials are gravel and cobbles with a median grain size (D 50 ) of 71.9 mm (0.236 ft). The geomorphic assessment at the time of the Level I and Level II site visit on July 25, 1996, indicated that the reach was stable. The Town Highway 1 crossing of Mill Brook is a 54-ft-long, two-lane bridge consisting of one 52-foot steel-beam span (Vermont Agency of Transportation, written communication, August 23, 1994). The bridge is supported by vertical, concrete abutments with spillthrough embankments. The channel is skewed approximately 15 degrees to the opening and the opening-skew-to-roadway is 15 degrees. The scour protection measures at the site were type-3 stone riprap (less than 48 inches diameter) on the spill-through embankments of each abutment and type-2 stone fill (less than 24 inches diameter) on the banks downstream. Additional details describing conditions at the site are included in the Level II Summary and Appendices D and E. Scour depths and rock rip-rap sizes were computed using the general guidelines described in Hydraulic Engineering Circular 18 (Richardson and others, 1995). Total scour at a highway crossing is comprised of three components: 1) long-term streambed degradation; 2) contraction scour (due to accelerated flow caused by a reduction in flow area at a bridge) and; 3) local scour (caused by accelerated flow around piers and abutments). Total scour is the sum of the three components. Equations are available to compute depths for contraction and local scour and a summary of the results of these computations follows. Contraction scour for all modelled flows ranged from 0.0 to 0.9 ft. The worst-case contraction scour occurred at the 500-year discharge. Abutment scour ranged from 3.6 to 7.1 ft. The worst-case abutment scour also occurred at the 500-year discharge. Additional information on scour depths and depths to armoring are included in the section titled “Scour Results”. Scoured-streambed elevations, based on the calculated scour depths, are presented in tables 1 and 2. A cross-section of the scour computed at the bridge is presented in figure 8. Scour depths were calculated assuming an infinite depth of erosive material and a homogeneous particle-size distribution. It is generally accepted that the Froehlich equation (abutment scour) gives “excessively conservative estimates of scour depths” (Richardson and others, 1995, p. 47). Usually, computed scour depths are evaluated in combination with other information including (but not limited to) historical performance during flood events, the geomorphic stability assessment, existing scour protection measures, and the results of the hydraulic analyses. Therefore, scour depths adopted by VTAOT may differ from the computed values documented herein.

Vermont↗

USGS1997

Level II scour analysis for Bridge 42 (BENNCYSCHL0042) on School Street, crossing Walloomsac River, Bennington, Vermont

This report provides the results of a detailed Level II analysis of scour potential at structure BENNCYSCHL0042 on the School Street crossing of the Walloomsac River, Bennington, Vermont (figures 1–8). A Level II study is a basic engineering analysis of the site, including a quantitative analysis of stream stability and scour (U.S. Department of Transportation, 1993). Results of a Level I scour investigation also are included in Appendix E of this report. A Level I investigation provides a qualitative geomorphic characterization of the study site. Information on the bridge, gleaned from Vermont Agency of Transportation (VTAOT) files, was compiled prior to conducting Level I and Level II analyses and is found in Appendix D. The site is in the Green Mountain section of the New England physiographic province in southwestern Vermont. The 30.1-mi 2 drainage area is a predominantly rural and forested basin. The bridge site is located within an urban setting in the Town of Bennington with buildings and residences on all overbanks. In the study area, the Walloomsac River has a straight channel with constructed channel banks downstream of the bridge. The channel is located on a delta and has a slope of approximately 0.02 ft/ft, an average channel top width of 37 ft and an average bank height of 6 ft. The predominant channel bed material is cobble with a median grain size (D 50 ) of 132 mm (0.435 ft). The geomorphic assessment at the time of the Level I and Level II site visit on August 6, 1996, indicated that the reach was stable. The School Street crossing of the Walloomsac River is a 36-ft-long, two-lane bridge consisting of one 33-foot concrete span (Vermont Agency of Transportation, written communication, December 13, 1995). The bridge is supported by vertical, concrete abutments with wingwalls. The channel is skewed approximately zero degrees to the opening and the opening-skew-to-roadway is also zero degrees. Scour countermeasures at the site include type-2 stone fill (less than 36 inches diameter) along both upstream banks and upstream wingwalls. Downstream banks are protected by stone walls extending from the downstream wingwalls to more than 100 feet downstream. Additional details describing conditions at the site are included in the Level II Summary and Appendices D and E. Scour depths and recommended rock rip-rap sizes were computed using the general guidelines described in Hydraulic Engineering Circular 18 (Richardson and others, 1995). Total scour at a highway crossing is comprised of three components: 1) long-term streambed degradation; 2) contraction scour (due to accelerated flow caused by a reduction in flow area at a bridge) and; 3) local scour (caused by accelerated flow around piers and abutments). Total scour is the sum of the three components. Equations are available to compute depths for contraction and local scour and a summary of the results of these computations follows. Contraction scour computed for all modelled flows was 0.0 ft. Computed left abutment scour ranged from 9.4 to 10.2 ft. with the worst-case scour occurring at the 500-year discharge. Computed right abutment scour ranged from 2.7 to 5.7 ft. with the worst-case scour occurring at the incipient roadway-overtopping discharge. Additional information on scour depths and depths to armoring are included in the section titled “Scour Results”. Scoured-streambed elevations, based on the calculated scour depths, are presented in tables 1 and 2. A cross-section of the scour computed at the bridge is presented in figure 8. Scour depths were calculated assuming an infinite depth of erosive material and a homogeneous particle-size distribution. It is generally accepted that the Froehlich equation (abutment scour) gives “excessively conservative estimates of scour depths” (Richardson and others, 1995, p. 47). Usually, computed scour depths are evaluated in combination with other information including (but not limited to) historical performance during flood events, the geomorphic stability assessment, existing scour protection measures, and the results of the hydraulic analyses. Therefore, scour depths adopted by VTAOT may differ from the computed values documented herein.

Vermont↗

USGS1997

Level II scour analysis for Bridge 30 (BRNATH00470030) on Town Highway 47, crossing Locust Creek, Barnard, Vermont

This report provides the results of a detailed Level II analysis of scour potential at structure BRNATH00470030 on Town Highway 47 crossing Locust Creek, Barnard, Vermont (figures 1–8). A Level II study is a basic engineering analysis of the site, including a quantitative analysis of stream stability and scour (U.S. Department of Transportation, 1993). Results of a Level I scour investigation also are included in Appendix E of this report. A Level I investigation provides a qualitative geomorphic characterization of the study site. Information on the bridge, gleaned from Vermont Agency of Transportation (VTAOT) files, was compiled prior to conducting Level I and Level II analyses and is found in Appendix D. The site is in the Green Mountain section of the New England physiographic province in central Vermont. The 4.18-mi 2 drainage area is a predominantly rural and forested basin. In the vicinity of the study site, the surface cover consists of trees, shrubs, and brush. In the study area, Locust Creek has an incised, sinuous channel with a slope of approximately 0.02 ft/ft, an average channel top width of 32 ft and an average bank height of 4 ft. The predominant channel bed material is gravel with a median grain size (D 50 ) of 49.5 mm (0.162 ft). The geomorphic assessment at the time of the Level I and Level II site visit on October 13, 1994, indicated that the reach was stable. The Town Highway 47 crossing of Locust Creek is a 28-ft-long, one-lane bridge consisting of one 25-foot concrete span (Vermont Agency of Transportation, written communication, August 23, 1994). The bridge is supported by vertical, concrete abutments with wingwalls. The channel is skewed approximately 40 degrees to the opening. Historical bridge data indicates that the opening-skew-to-roadway is 45 degrees, but 35 degrees was computed by use of survey data from this study. A minor scour hole, 0.5 ft deeper than the mean thalweg depth was observed along the left abutment wall during the Level I assessment. The scour protection measures at the site were type-2 stone fill (less than 36 inches diameter) on the upstream wingwalls. There also is type-3 stone fill on the downstream right wingwall. Additional details describing conditions at the site are included in the Level II Summary and Appendices D and E. Scour depths and recommended rock rip-rap sizes were computed using the general guidelines described in Hydraulic Engineering Circular 18 (Richardson and others, 1995). Total scour at a highway crossing is comprised of three components: 1) long-term streambed degradation; 2) contraction scour (due to accelerated flow caused by a reduction in flow area at a bridge) and; 3) local scour (caused by accelerated flow around piers and abutments). Total scour is the sum of the three components. Equations are available to compute depths for contraction and local scour and a summary of the results of these computations follows. Contraction scour for all modelled flows ranged from 0.0 to 1.4 feet. The worst-case contraction scour occurred at the 500-year discharge. Abutment scour ranged from 2.3 to 8.9 feet. The worst-case abutment scour occurred at the 100-year discharge at the right abutment. Additional information on scour depths and depths to armoring are included in the section titled “Scour Results”. Scoured-streambed elevations, based on the calculated scour depths, are presented in tables 1 and 2. A cross-section of the scour computed at the bridge is presented in figure 8. Scour depths were calculated assuming an infinite depth of erosive material and a homogeneous particle-size distribution. It is generally accepted that the Froehlich equation (abutment scour) gives “excessively conservative estimates of scour depths” (Richardson and others, 1995, p. 47). Usually, computed scour depths are evaluated in combination with other information including (but not limited to) historical performance during flood events, the geomorphic stability assessment, existing scour protection measures, and the results of the hydraulic analyses. Therefore, scour depths adopted by VTAOT may differ from the computed values documented herein.

Vermont↗

USGS1997

Level II scour analysis for Bridge 2 (STAMVT01000002) on State Route 100 crossing Roaring Brook, Stamford, Vermont

This report provides the results of a detailed Level II analysis of scour potential at structure STAMVT01000002 on State Route 100 crossing Roaring Brook, Stamford, Vermont (figures 1–8). A Level II study is a basic engineering analysis of the site, including a quantitative analysis of stream stability and scour (U.S. Department of Transportation, 1993). Results of a Level I scour investigation also are included in Appendix E of this report. A Level I investigation provides a qualitative geomorphic characterization of the study site. Information on the bridge, gleaned from Vermont Agency of Transportation (VTAOT) files, was compiled prior to conducting Level I and Level II analyses and is found in Appendix D. The site is in the Green Mountain section of the New England physiographic province in Southwestern Vermont. The 8.26-mi 2 drainage area is in a predominantly rural and forested basin. In the vicinity of the study site, the surface cover consists of houses with grass lawns, and trees on the right overbank areas upstream and downstream of the bridge. The left overbank areas upstream and downstream of the bridge are covered with trees and brush. In the study area, Roaring Brook has a straight channel with a slope of approximately 0.02 ft/ft, an average channel top width of 56 ft and an average bank height of 5 ft. The channel bed materials range from gravel to boulders with a median grain size (D 50 ) of 53.7 mm (0.176 ft). The geomorphic assessment at the time of the Level I and Level II site visit on July 31, 1996, indicated that the reach was aggraded. The State Route 100 crossing of Roaring Brook is a 44-ft-long, two-lane bridge consisting of one 42-foot steel-beam span (Vermont Agency of Transportation, written communication, September 28, 1995). The bridge is supported by vertical, concrete abutments with wingwalls. The channel is skewed approximately 5 degrees to the opening and the opening-skew-to-roadway is 5 degrees. Scour protection measures at the site were type-2 stone fill (less than 36 inches diameter) on the upstream banks and wingwalls, type-3 (less than 48 inches diameter) on the downstream wingwalls, and artificial levees made from a variety of materials on the downstream banks. Additional details describing conditions at the site are included in the Level II Summary and Appendices D and E. Scour depths and rock rip-rap sizes were computed using the general guidelines described in Hydraulic Engineering Circular 18 (Richardson and others, 1995). Total scour at a highway crossing is comprised of three components: 1) long-term streambed degradation; 2) contraction scour (due to accelerated flow caused by a reduction in flow area at a bridge) and; 3) local scour (caused by accelerated flow around piers and abutments). Total scour is the sum of the three components. Equations are available to compute depths for contraction and local scour and a summary of the results of these computations follows. Contraction scour for all modelled flows ranged from 0.0 to 0.8 feet. The worst-case contraction scour occurred at the 100-year discharge. Abutment scour ranged from 4.2 to 9.3 feet. The worst-case abutment scour occurred at the 500-year discharge at the left abutment. Additional information on scour depths and depths to armoring are included in the section titled “Scour Results”. Scoured-streambed elevations, based on the calculated scour depths, are presented in tables 1 and 2. A cross-section of the scour computed at the bridge is presented in figure 8. Scour depths were calculated assuming an infinite depth of erosive material and a homogeneous particle-size distribution. It is generally accepted that the Froehlich equation (abutment scour) gives “excessively conservative estimates of scour depths” (Richardson and others, 1995, p. 47). Usually, computed scour depths are evaluated in combination with other information including (but not limited to) historical performance during flood events, the geomorphic stability assessment, existing scour protection measures, and the results of the hydraulic analyses. Therefore, scour depths adopted by VTAOT may differ from the computed values documented herein.

Vermont↗

USGS1997

Level II scour analysis for Bridge 19 (CHARTH00390019) on Town Highway 39, crossing Mad Brook, Charleston, Vermont

This report provides the results of a detailed Level II analysis of scour potential at structure CHARTH00390019 on Town Highway 39 crossing Mad Brook, Charleston, Vermont (figures 1–8). A Level II study is a basic engineering analysis of the site, including a quantitative analysis of stream stability and scour (U.S. Department of Transportation, 1993). Results of a Level I investigation also are included in this report in Appendix E. A Level I study provides a qualitative geomorphic characterization of the study site. Information on the bridge, gleaned from Vermont Agency of Transportation (VTAOT) files, was compiled prior to conducting Level I and Level II analyses and is found in Appendix D. The site is in the White Mountain section of the New England physiographic province in northeastern Vermont in the town of Charleston. The 6.54-mi 2 drainage area is in a predominantly rural and forested basin. In the vicinity of the study site, the surface cover is forest except for the upstream left side which is covered primarily with shrubs and brush. The immediate banks have dense woody vegetation. In the study area, Mad Brook has an incised, sinuous channel with a slope of approximately 0.023 ft/ft, an average channel top width of 40 ft and an average channel depth of 4 ft. The predominant channel bed material is cobble with a median grain size (D 50 ) of 135.0 mm (0.443 ft). The geomorphic assessment on October 26, 1994 indicated that the reach was laterally unstable due to long-term lateral migration of the channel. Data collection for the level II analysis was accomplished on October 26, 1994 and July 24, 1995. The Town Highway 39 crossing of Mad Brook is a 34-ft-long, two-lane bridge consisting of one 31-foot steel-beam span (Vermont Agency of Transportation, written communication, August 4, 1994). The bridge is supported by vertical, concrete abutments with wingwalls. The channel is skewed approximately 40 degrees to the opening while the opening-skew-to-roadway is 45 degrees. A scour hole 1.5 ft deeper than the mean thalweg depth was observed along the right abutment during the Level I assessment. The scour protection measures evident at the site were type-2 stone fill (less than 36 inches diameter) on the upstream left wingwall and upstream end of the left abutment wall. Type-3 stone fill (less than 48 inches diameter) was noted on the upstream right wingwall and the upstream side of the left road approach embankment. Additional details describing conditions at the site are included in the Level II Summary and Appendices D and E. Scour depths and rock rip-rap sizes were computed using the general guidelines described in Hydraulic Engineering Circular 18 (Richardson and others, 1995). Total scour at a highway crossing is comprised of three components: 1) long-term streambed degradation; 2) contraction scour (due to accelerated flow caused by a reduction in flow area at a bridge) and; 3) local scour (caused by accelerated flow around piers and abutments). Total scour is the sum of the three components. Equations are available to compute depths for contraction and local scour and a summary of the results of these computations follows. Contraction scour for all modelled flows was 0.0 ft. Abutment scour ranged from 9.5 to 16.7 ft. The worst-case abutment scour occurred at the 500-year discharge. Additional information on scour depths and depths to armoring are included in the section titled “Scour Results”. Scoured-streambed elevations, based on the calculated scour depths, are presented in tables 1 and 2. A cross-section of the scour computed at the bridge is presented in figure 8. Scour depths were calculated assuming an infinite depth of erosive material and a homogeneous particle-size distribution. It is generally accepted that the Froehlich equation (abutment scour) gives “excessively conservative estimates of scour depths” (Richardson and others, 1995, p. 47). Usually, computed scour depths are evaluated in combination with other information including (but not limited to) historical performance during flood events, the geomorphic stability assessment, existing scour protection measures, and the results of the hydraulic analyses. Therefore, scour depths adopted by VTAOT may differ from the computed values documented herein.

Vermont↗

USGS1997

Level II scour analysis for Bridge 7 (CHARTH00010007) on Town Highway 1, crossing Mad Brook, Charleston, Vermont

This report provides the results of a detailed Level II analysis of scour potential at structure CHARTH00010007 on town highway 1 crossing Mad Brook, Charleston, Vermont (figures 1–8). A Level II study is a basic engineering analysis of the site, including a quantitative analysis of stream stability and scour (U.S. Department of Transportation, 1993). Results of a Level I scour investigation also are included in Appendix E of this report. A Level I investigation provides a qualitative geomorphic characterization of the study site. Information on the bridge, gleaned from Vermont Agency of Transportation (VTAOT) files, was compiled prior to conducting Level I and Level II analyses and is found in Appendix D. The site is in the White Mountain section of the New England physiographic province in north-central Vermont in the town of Charleston. The 6.59-mi 2 drainage area is in a predominantly rural and forested basin. In the vicinity of the study site, the surface cover is pasture except for the upstream left bank, which is forest. The stream banks are tree covered upstream and on the downstream left bank side. In the study area, Mad Brook has an incised, sinuous channel with a slope of approximately 0.01 ft/ft, an average channel top width of 41 ft and an average channel depth of 5 ft. The predominant channel bed materials range from gravel to boulders with a median grain size (D 50 ) of 105 mm (0.344 ft). The geomorphic assessment at the time of the Level I and Level II site visit on October 28, 1994, indicated that the reach was stable. The town highway 1 crossing of Mad Brook is a 27-ft-long, two-lane bridge consisting of one 25-foot concrete T-beam span (Vermont Agency of Transportation, written communication, August 4, 1994). The bridge is supported by vertical, concrete abutments with wingwalls. The channel is skewed approximately 10 degrees to the opening. The opening-skew-to-roadway computed from surveyed data is 5 degrees, but historical bridge records indicate this angle is closer to 10 degrees. There was scour evident during the Level I assessment due to the presence of two subfootings at the base of each abutment wall. Although the subfootings may have been constructed at the same time as the abutment walls, the subfootings may have been constructed at a later time in response to streambed degradation under the bridge. The right abutment was noted as undermined during the Level I assessment. Scour protection measures at the site were type-1 stone fill (less than 12 inches diameter) on the upstream right and downstream road embankments and type-2 stone fill on each wingwall and the downstream left bank. Additional details describing conditions at the site are included in the Level II Summary and Appendices D and E. Scour depths and rock rip-rap sizes were computed using the general guidelines described in Hydraulic Engineering Circular 18 (Richardson and others, 1995). Total scour at a highway crossing is comprised of three components: 1) long-term streambed degradation; 2) contraction scour (due to accelerated flow caused by a reduction in flow area at a bridge) and; 3) local scour (caused by accelerated flow around piers and abutments). Total scour is the sum of the three components. Equations are available to compute depths for contraction and local scour and a summary of the results of these computations follows. Contraction scour for all modelled flows ranged from 0.0 to 0.3 ft. The worst-case contraction scour occurred at the incipient overtopping discharge, which was less than the 100-year discharge. Abutment scour ranged from 6.2 to 9.4 ft. The worst-case abutment scour for the right abutment was 9.4 feet at the 100-year discharge. The worst-case abutment scour for the left abutment was 8.6 feet at the incipient overtopping discharge. Additional information on scour depths and depths to armoring are included in the section titled “Scour Results”. Scoured-streambed elevations, based on the calculated scour depths, are presented in tables 1 and 2. A cross-section of the scour computed at the bridge is presented in figure 8. Scour depths were calculated assuming an infinite depth of erosive material and a homogeneous particle-size distribution. It is generally accepted that the Froehlich equation (abutment scour) gives “excessively conservative estimates of scour depths” (Richardson and others, 1995, p. 47). Usually, computed scour depths are evaluated in combination with other information including (but not limited to) historical performance during flood events, the geomorphic stability assessment, existing scour protection measures, and the results of the hydraulic analyses. Therefore, scour depths adopted by VTAOT may differ from the computed values documented herein.

Vermont↗

USGS1997

Level II scour analysis for Bridge 80 (JAMAVT01000080) on State Highway 100, crossing the West River, Jamaica, Vermont

This report provides the results of a detailed Level II analysis of scour potential at structure JAMAVT01000080 on State Route 100 crossing the West River, Jamaica, Vermont (figures 1–8). A Level II study is a basic engineering analysis of the site, including a quantitative analysis of stream stability and scour (U.S. Department of Transportation, 1993). Results of a Level I scour investigation also are included in Appendix E of this report. A Level I investigation provides a qualitative geomorphic characterization of the study site. Information on the bridge, gleaned from Vermont Agency of Transportation (VTAOT) files, was compiled prior to conducting Level I and Level II analyses and is found in Appendix D. The site is in the Green Mountain section of the New England physiographic province in southern Vermont. The 227-mi 2 drainage area is in a predominantly rural and forested basin. In the vicinity of the study site, the surface cover is pasture on the upstream left bank and downstream of the bridge while the immediate banks have dense woody vegetation. The upstream right bank of the bridge is forested. In the study area, the West River has an incised, straight channel with a slope of approximately 0.01 ft/ft, an average channel top width of 309 ft and an average bank height of 10 ft. The channel bed material is predominantly cobble with a median grain size (D 50 ) of 109 mm (0.359 ft). The geomorphic assessment at the time of the Level I and Level II site visit on August 13, 1996, indicated that the reach was stable. The State Route 100 crossing of the West River is a 246-ft-long, one-lane steel thru-truss bridge consisting of three spans, the longest is 161-feet (Vermont Agency of Transportation, written communication, March 30, 1995). The bridge is supported by vertical, concrete abutments and two piers. The channel is skewed approximately 5 degrees to the opening while there is no opening-skew-to-roadway. A scour hole 3 ft deeper than the mean thalweg depth was observed along the streamward (right) side of the left pier during the Level I assessment. A scour hole 5 ft deeper than the mean thalweg depth was observed along the streamward (left) side of the right pier during the Level I assessment. The only scour protection measure at the site was type-2 stone fill (less than 36 inches diameter) along the left and right bank below the abutments forming a “spill-through” slope at each abutment. Additional details describing conditions at the site are included in the Level II Summary and Appendices D and E. Scour depths and recommended rock rip-rap sizes were computed using the general guidelines described in Hydraulic Engineering Circular 18 (Richardson and others, 1995). Total scour at a highway crossing is comprised of three components: 1) long-term streambed degradation; 2) contraction scour (due to accelerated flow caused by a reduction in flow area at a bridge) and; 3) local scour (caused by accelerated flow around piers and abutments). Total scour is the sum of the three components. Equations are available to compute depths for contraction and local scour and a summary of the results of these computations follows. There was no computed contraction scour. Abutment scour ranged from 15.8 to 23.9 ft. The worst-case abutment scour occurred at the 500-year discharge. Pier scour ranged from 9.5 to 22.8 ft. The worst-case pier scour occurred at the 500-year discharge. Additional information on scour depths and depths to armoring are included in the section titled “Scour Results”. Scoured-streambed elevations, based on the calculated scour depths, are presented in tables 1 and 2. A cross-section of the scour computed at the bridge is presented in figure 8. Scour depths were calculated assuming an infinite depth of erosive material and a homogeneous particle-size distribution. It is generally accepted that the Froehlich equation (abutment scour) gives “excessively conservative estimates of scour depths” (Richardson and others, 1995, p. 47). Usually, computed scour depths are evaluated in combination with other information including (but not limited to) historical performance during flood events, the geomorphic stability assessment, existing scour protection measures, and the results of the hydraulic analyses. Therefore, scour depths adopted by VTAOT may differ from the computed values documented herein.

Vermont↗

USGS1997

Level II scour analysis for Bridge 8 (STAMVT01000008) on State Highway 100, crossing the North Branch of the Hoosic River, Stamford, Vermont

This report provides the results of a detailed Level II analysis of scour potential at structure STAMVT01000008 on Vermont Highway 100 crossing the North Branch of the Hoosic River, Stamford, Vermont (figures 1–8). A Level II study is a basic engineering analysis of the site, including a quantitative analysis of stream stability and scour (U.S. Department of Transportation, 1993). Results of a Level I scour investigation also are included in Appendix E of this report. A Level I investigation provides a qualitative geomorphic characterization of the study site. Information on the bridge, gleaned from Vermont Agency of Transportation (VTAOT) files, was compiled prior to conducting Level I and Level II analyses and is found in Appendix D. The site is in the Green Mountain section of the New England physiographic province in southern Vermont. The 6.8-mi 2 drainage area is in a predominantly rural and forested basin. In the vicinity of the study site, the upstream right bank surface cover is short grass and the upstream left bank is a sand/gravel lot while the immediate banks are covered by shrubs and trees. Downstream of the bridge banks are forested. In the study area, the North Branch of the Hoosic River has an incised, sinuous channel with a slope of approximately 0.02 ft/ft, an average channel top width of 37 ft and an average bank height of 3 ft. The channel bed material is predominantly cobble with a median grain size (D 50 ) of 88.0 mm (0.289 ft). The geomorphic assessment at the time of the Level I and Level II site visit on August 1, 1996, indicated that the reach was laterally unstable. The Vermont Highway 100 crossing of the North Branch of the Hoosic River is a 39-ft-long, two-lane bridge consisting of one 37-foot steel-beam span (Vermont Agency of Transportation, written communication, November 1, 1995). The bridge is supported by vertical, concrete abutments. The channel is skewed approximately 20 degrees to the opening while the opening-skew-to-roadway is 15 degrees. A scour hole 2.5 ft deeper than the mean thalweg depth was observed along the upstream end of the right abutment during the Level I assessment. The only scour protection measure at the site was type-3 stone fill (less than 48 inches diameter) at the downstream ends of the left and right abutments extending downstream along the left bank for 13 feet and along the right bank for 16 feet. The plans show stone fill placed at the upstream ends of the abutments. The protection at the upstream end of the right abutment has failed due to stream migration towards the right bank. The protection at the upstream end of the left abutment was not detected due to the sand/gravel pile, for District 1 maintenance, migrating into the channel (Figure 3). Additional details describing conditions at the site are included in the Level II Summary and Appendices D and E. Scour depths and rock rip-rap sizes were computed using the general guidelines described in Hydraulic Engineering Circular 18 (Richardson and others, 1995). Total scour at a highway crossing is comprised of three components: 1) long-term streambed degradation; 2) contraction scour (due to accelerated flow caused by a reduction in flow area at a bridge) and; 3) local scour (caused by accelerated flow around piers and abutments). Total scour is the sum of the three components. Equations are available to compute depths for contraction and local scour and a summary of the results of these computations follows. Contraction scour for all modelled flows ranged from 0.6 to 3.0 ft. The worst-case contraction scour occurred at the 500-year discharge. Left abutment scour ranged from 14.4 to 17.8 ft. Right abutment scour ranged from 8.1 to 11.1 ft. The worst-case abutment scour occurred at the 500-year discharge. Additional information on scour depths and depths to armoring are included in the section titled “Scour Results”. Scoured-streambed elevations, based on the calculated scour depths, are presented in tables 1 and 2. A cross-section of the scour computed at the bridge is presented in figure 8. Scour depths were calculated assuming an infinite depth of erosive material and a homogeneous particle-size distribution. It is generally accepted that the Froehlich equation (abutment scour) gives “excessively conservative estimates of scour depths” (Richardson and others, 1995, p. 47). Usually, computed scour depths are evaluated in combination with other information including (but not limited to) historical performance during flood events, the geomorphic stability assessment, existing scour protection measures, and the results of the hydraulic analyses. Therefore, scour depths adopted by VTAOT may differ from the computed values documented herein.

Vermont↗

USGS1997

Level II scour analysis for Bridge 6 (STAMVT01000006) on State Route 100, crossing the North Branch of the Hoosic River, Stamford, Vermont

This report provides the results of a detailed Level II analysis of scour potential at structure STAMVT01000006 on Vermont Highway 100 crossing the North Branch of the Hoosic River, Stamford, Vermont (figures 1–8). A Level II study is a basic engineering analysis of the site, including a quantitative analysis of stream stability and scour (U.S. Department of Transportation, 1993). Results of a Level I scour investigation also are included in Appendix E of this report. A Level I investigation provides a qualitative geomorphic characterization of the study site. Information on the bridge, gleaned from Vermont Agency of Transportation (VTAOT) files, was compiled prior to conducting Level I and Level II analyses and is found in Appendix D. The site is in the Green Mountain section of the New England physiographic province in southern Vermont. The 8.61-mi 2 drainage area is in a predominantly rural and forested basin. In the vicinity of the study site, the surface cover is grass with forest along the immediate banks throughout the reach. In the study area, the North Branch of the Hoosic River has an incised, sinuous channel with a slope of approximately 0.02 ft/ft, an average channel top width of 44 ft and an average bank height of 4 ft. The channel bed material ranges from sand to boulder with a median grain size (D 50 ) of 97.4 mm (0.320 ft). The geomorphic assessment at the time of the Level I and Level II site visit on July 31, 1996, indicated that the reach was stable. The Vermont Highway 100 crossing of the North Branch of the Hoosic River is a 99-ft-long, two-lane bridge consisting of one 97-foot steel-beam span (Vermont Agency of Transportation, written communication, September 28, 1995). The bridge is supported by vertical, concrete abutments with wingwalls. The channel is skewed approximately 60 degrees to the opening and the opening-skew-to-roadway is also 60 degrees. The scour protection measures at the site included type-1 stone fill (less than 12 inches diameter) along the downstream left bank. Type-2 (less than 36 inches diameter) stone fill was found along the upstream left bank and the downsteam right bank. Additional details describing conditions at the site are included in the Level II Summary and Appendices D and E. Scour depths and rock rip-rap sizes were computed using the general guidelines described in Hydraulic Engineering Circular 18 (Richardson and others, 1995). Total scour at a highway crossing is comprised of three components: 1) long-term streambed degradation; 2) contraction scour (due to accelerated flow caused by a reduction in flow area at a bridge) and; 3) local scour (caused by accelerated flow around piers and abutments). Total scour is the sum of the three components. Equations are available to compute depths for contraction and local scour and a summary of the results of these computations follows. Contraction scour for all modelled flows ranged from 0.7 to 2.1 ft. The worst-case contraction scour occurred at the 500-year discharge. Abutment scour ranged from 18.8 to 19.7 ft along the right abutment and from 2.8 to 6.8 ft along the left abutment. The worst-case abutment scour occurred at the 500-year discharge. Additional information on scour depths and depths to armoring are included in the section titled “Scour Results”. Scoured-streambed elevations, based on the calculated scour depths, are presented in tables 1 and 2. A cross-section of the scour computed at the bridge is presented in figure 8. Scour depths were calculated assuming an infinite depth of erosive material and a homogeneous particle-size distribution. It is generally accepted that the Froehlich equation (abutment scour) gives “excessively conservative estimates of scour depths” (Richardson and others, 1995, p. 47). Usually, computed scour depths are evaluated in combination with other information including (but not limited to) historical performance during flood events, the geomorphic stability assessment, existing scour protection measures, and the results of the hydraulic analyses. Therefore, scour depths adopted by VTAOT may differ from the computed values documented herein.

Vermont↗

USGS1997

Level II scour analysis for Bridge 23 (CRAFTH00390023) on Town Highway 39, crossing the Black River, Craftsbury, Vermont

This report provides the results of a detailed Level II analysis of scour potential at structure CRAFTH00390023 on town highway 39 crossing the Black River, Craftsbury, Vermont (figures 1–8). A Level II study is a basic engineering analysis of the site, including a quantitative analysis of stream stability and scour (U.S. Department of Transportation, 1993). A Level I assessment is included in Appendix E of this report. A Level I assessment provides a qualitative geomorphic characterization of the study site. Information on the bridge, gleaned from VTAOT files, was compiled prior to conducting Level I and Level II analyses and is provided in Appendix D. The site is in the New England Upland physiographic province of North-central Vermont in the town of Craftsbury. The 30.9-mi 2 drainage area is in a predominantly rural and forested basin with some pasture grassland on the valley bottom. In the vicinity of the study site, the banks have very little woody vegetation coverage except for the downstream left bank, which has some trees and brush coverage. In the study area, the Black River has an meandering channel with a slope of approximately 0.0004 ft/ft, an average channel top width of 62 ft and an average channel depth of 3 ft. The predominant channel bed materials are sand and gravel with a median grain size (D 50 ) of 0.73 mm (0.0024 ft). The geomorphic assessment at the time of the Level I and Level II site visit on June 6, 1995, indicated that the reach was laterally unstable. The town highway 39 crossing of the Black River is a 65-ft-long, two-lane bridge consisting of three spans with a maximum span of 38-feet (Vermont Agency of Transportation, written communication, August 24, 1994). The bridge is supported by vertical, concrete abutments and two stone piers with concrete caps. The channel is skewed approximately 10 degrees to the opening while the opening-skew-to-roadway is 10 degrees in the opposite direction. The scour protection measures at the site were type-1 stone fill (less than 12 inches diameter) on the upstream left and right roadway embankments and between the right pier and right abutment wall. Type-2 (less than 36 inches diameter) stone fill was evident on the upstream left bank, downstream right bank, between the left pier and left abutment wall, and streamward of the right pier. Additional details describing conditions at the site are included in the Level II Summary and Appendices D and E. Scour depths and rock rip-rap sizes were computed using the general guidelines described in Hydraulic Engineering Circular 18 (Richardson and others, 1995). Total scour at a highway crossing is comprised of three components: 1) long-term aggradation or degradation; 2) contraction scour (due to reduction in flow area caused by a bridge) and; 3) local scour (caused by accelerated flow around piers and abutments). Total scour is the sum of the three components. Equations are available to compute scour depths for contraction and local scour and a summary of the results follows. Contraction scour for all modelled flows ranged from 20.1 to 25.2 and the worst-case contraction scour occurred at the 500-year discharge. Although this bridge has two piers, the flow through the spans between each abutment and pier is assumed to be negligible. Hence, abutment scour was computed assuming the forces contributing to scour actually occur on the main-span sides of each pier in this case. Abutment scour ranged from 8.8 to 10.6 and the worst-case abutment scour occurred at the 500-year discharge. Scour depths and depths to armoring are summarized on p. 14 in the section titled “Scour Results”. Scour elevations, based on the calculated depths are presented in tables 1 and 2. A graph of the scour elevations is presented in figure 8. Scour depths were calculated assuming an infinite depth of erosive material and a homogeneous particle-size distribution. It is generally accepted that the Froehlich equation (abutment scour) gives “excessively conservative estimates of scour depths” (Richardson and others, 1995, p. 47). Usually, computed scour depths are evaluated in combination with other information including (but not limited to) historical performance during flood events, the geomorphic stability assessment, existing scour protection measures, and the results of the hydraulic analyses. Therefore, scour depths adopted by VTAOT may differ from the computed values documented herein.

Vermont↗

USGS1997

Level II scour analysis for Bridge 30 (NEWFVT00300013) on Vermont Highway 30, crossing Smith Brook, Newfane, Vermont

This report provides the results of a detailed Level II analysis of scour potential at structure NEWFVT00300013 on State Route 30 crossing Smith Brook, Newfane, Vermont (figures 1–8). A Level II study is a basic engineering analysis of the site, including a quantitative analysis of stream stability and scour (U.S. Department of Transportation, 1993). Results of a Level I scour investigation also are included in Appendix E of this report. A Level I investigation provides a qualitative geomorphic characterization of the study site. Information on the bridge, gleaned from Vermont Agency of Transportation (VTAOT) files, was compiled prior to conducting Level I and Level II analyses and is found in Appendix D. The site is in the New England Upland section of the New England physiographic province in southeastern Vermont. The 9.38-mi 2 drainage area is in a predominantly rural and forested basin. In the vicinity of the study site, the surface cover is grass and shrubs except for the upstream right bank which is forested. In the study area, Smith Brook has an incised, sinuous channel with a slope of approximately 0.01 ft/ft, an average channel top width of 53 ft and an average bank height of 5 ft. The channel bed material is predominantly cobbles with a median grain size (D 50 ) of 79.5 mm (0.261 ft). The geomorphic assessment at the time of the Level I and Level II site visit on August 20, 1996, indicated that the reach was stable. The State Route 30 crossing of Smith Brook is a 69-ft-long, two-lane bridge consisting of one 66-foot steel-beam span (Vermont Agency of Transportation, written communication, March 30, 1995). The bridge is supported by vertical, concrete abutments with wingwalls. The channel is skewed approximately 45 degrees to the opening while the opening-skew-to- roadway is 55 degrees. The scour protection measures at the site were type-1 stone fill (less than 12 inches diameter) along the upstream right bank. There was also type-2 stone fill (less than 36 inches diameter) along the upstream left bank. A stone wall extends to 72 feet upstream from the end of the upstream left wingwall. There is another stone wall along the upstream right bank. Additional details describing conditions at the site are included in the Level II Summary and Appendices D and E. Scour depths and recommended rock rip-rap sizes were computed using the general guidelines described in Hydraulic Engineering Circular 18 (Richardson and others, 1995). Total scour at a highway crossing is comprised of three components: 1) long-term streambed degradation; 2) contraction scour (due to accelerated flow caused by a reduction in flow area at a bridge) and; 3) local scour (caused by accelerated flow around piers and abutments). Total scour is the sum of the three components. Equations are available to compute depths for contraction and local scour and a summary of the results of these computations follows. Contraction scour for all modelled flows ranged from 0.0 to 0.8 ft. The worst-case contraction scour occurred at the 500-year discharge. Abutment scour ranged from 14.4 to 18.2 ft. The worst-case abutment scour occurred at the 500-year discharge. Additional information on scour depths and depths to armoring are included in the section titled “Scour Results”. Scoured-streambed elevations, based on the calculated scour depths, are presented in tables 1 and 2. A cross-section of the scour computed at the bridge is presented in figure 8. Scour depths were calculated assuming an infinite depth of erosive material and a homogeneous particle-size distribution. It is generally accepted that the Froehlich equation (abutment scour) gives “excessively conservative estimates of scour depths” (Richardson and others, 1995, p. 47). Usually, computed scour depths are evaluated in combination with other information including (but not limited to) historical performance during flood events, the geomorphic stability assessment, existing scour protection measures, and the results of the hydraulic analyses. Therefore, scour depths adopted by VTAOT may differ from the computed values documented herein.

Vermont↗

USGS1997

Level II scour analysis for Bridge 27 (ANDOTH00290027) on Town Highway 29, crossing Middle Branch Williams River, Andover, Vermont

This report provides the results of a detailed Level II analysis of scour potential at structure ANDOTH00290027 on Town Highway 29 crossing the Middle Branch Williams River, Andover, Vermont (figures 1–8). A Level II study is a basic engineering analysis of the site, including a quantitative analysis of stream stability and scour (U.S. Department of Transportation, 1993). Results of a Level I scour investigation also are included in Appendix E of this report. A Level I investigation provides a qualitative geomorphic characterization of the study site. Information on the bridge, gleaned from Vermont Agency of Transportation (VTAOT) files, was compiled prior to conducting Level I and Level II analyses and is found in Appendix D. The site is in the Green Mountain section of the New England physiographic province in central Vermont. The 12.7-mi 2 drainage area is in a predominantly rural and forested basin. In the vicinity of the study site, the surface cover is pasture on the left bank upstream of the bridge while the immediate bank has woody vegetation. The surface cover on the upstream right bank is forest. Downstream of the bridge the left bank is pasture and the right bank has woody vegetation. In the study area, the Middle Branch Williams River has an incised, straight channel with a slope of approximately 0.009 ft/ft, an average channel top width of 63 ft and an average bank height of 5 ft. The channel bed material ranges from sand to cobble with a median grain size (D 50 ) of 64.7 mm (0.212 ft). The geomorphic assessment at the time of the Level I and Level II site visit on September 10, 1996, indicated that the reach was stable. The Town Highway 29 crossing of the Middle Branch Williams River is a 34-ft-long, two- lane bridge consisting of one 32-foot steel-beam span (Vermont Agency of Transportation, written communication, April 5, 1995). The bridge is supported by vertical, concrete abutments with wingwalls. The channel is skewed approximately 25 degrees to the opening while the opening-skew-to-roadway is 0 degrees. A scour hole 1.5 ft deeper than the mean thalweg depth was observed along the left abutment during the Level I assessment. Scour protection measures at the site include type- 2 stone fill (less than 36 inches diameter) along the upstream right bank and downstream left bank and around the upstream left and right wingwalls. Type- 3 stone fill (less than 48 inches diameter) is located along the base of the left abutment in the scour hole, at the end of the downstream left wingwall and along the upstream left bank. Additional details describing conditions at the site are included in the Level II Summary and Appendices D and E. Scour depths and recommended rock rip-rap sizes were computed using the general guidelines described in Hydraulic Engineering Circular 18 (Richardson and others, 1995). Total scour at a highway crossing is comprised of three components: 1) long-term streambed degradation; 2) contraction scour (due to accelerated flow caused by a reduction in flow area at a bridge) and; 3) local scour (caused by accelerated flow around piers and abutments). Total scour is the sum of the three components. Equations are available to compute depths for contraction and local scour and a summary of the results of these computations follows. Contraction scour for all modelled flows ranged from 0.4 to 0.9 ft. The worst-case contraction scour occurred at the incipient-overtopping discharge and the 100-year discharge. Abutment scour ranged from 10.7 to 13.6 ft. The worst-case abutment scour occurred at the 500-year discharge. Additional information on scour depths and depths to armoring are included in the section titled “Scour Results”. Scoured-streambed elevations, based on the calculated scour depths, are presented in tables 1 and 2. A cross-section of the scour computed at the bridge is presented in figure 8. Scour depths were calculated assuming an infinite depth of erosive material and a homogeneous particle-size distribution. It is generally accepted that the Froehlich equation (abutment scour) gives “excessively conservative estimates of scour depths” (Richardson and others, 1995, p. 47). Usually, computed scour depths are evaluated in combination with other information including (but not limited to) historical performance during flood events, the geomorphic stability assessment, existing scour protection measures, and the results of the hydraulic analyses. Therefore, scour depths adopted by VTAOT may differ from the computed values documented herein.

Vermont↗

USGS1997

Level II scour analysis for Bridge 12 (HUNTTH00010012) on Town Highway 001, crossing Brush Brook, Huntington, Vermont

This report provides the results of a detailed Level II analysis of scour potential at structure HUNTTH00010012 on Town Highway 1 crossing Brush Brook, Huntington, Vermont (figures 1–9). A Level II study is a basic engineering analysis of the site, including a quantitative analysis of stream stability and scour (U.S. Department of Transportation, 1993). Results of a Level I scour investigation also are included in Appendix E of this report. A Level I investigation provides a qualitative geomorphic characterization of the study site. Information on the bridge, gleaned from Vermont Agency of Transportation (VTAOT) files, was compiled prior to conducting Level I and Level II analyses and is found in Appendix D. In August 1976, Hurricane Belle caused flooding at this site which resulted in road and bridge damage (figures 7-8). This was approximately a 25-year flood event based on flood- frequency data contained in the Flood Insurance Study for the Town of Huntington (U.S. Department of Housing and Urban Development, 1978). The site is in the Green Mountain section of the New England physiographic province in central Vermont. The 9.19-mi 2 drainage area is in a predominantly rural and forested basin. In the vicinity of the study site, the surface cover is pasture while the immediate banks have some woody vegetation. In the study area, the Brush Brook has a sinuous channel with a slope of approximately 0.02 ft/ft, an average channel top width of 62 ft and an average bank height of 5 ft. The channel bed material ranges from gravel to cobble with a median grain size (D 50 ) of 100.0 mm (0.328 ft). The geomorphic assessment at the time of the Level I and Level II site visit on June 25, 1996, indicated that the reach was stable. The Town Highway 1 crossing of Brush Brook is a 64-ft-long, two-lane bridge consisting of one 62-foot steel-stringer span (Vermont Agency of Transportation, written communication, November 30, 1995). The bridge is supported by vertical, concrete abutments with wingwalls. The channel is skewed approximately 10 degrees to the opening while the opening-skew-to-roadway is 6 degrees. Channel scour 2.2 ft deeper than the mean thalweg depth was observed along the upstream right bank and along the base of the spill-through protection for the right abutment during the Level I assessment. Scour protection measured at the site was type-2 stone fill (less than 36 inches diameter) along the upstream left and right banks and in front of all four wingwalls. In front of the abutments, there was type-3 stone fill (less than 48 inches diameter) forming a spill-through slope. Additional details describing conditions at the site are included in the Level II Summary and Appendices D and E. Scour depths and recommended rock rip-rap sizes were computed using the general guidelines described in Hydraulic Engineering Circular 18 (Richardson and others, 1995). Total scour at a highway crossing is comprised of three components: 1) long-term streambed degradation; 2) contraction scour (due to accelerated flow caused by a reduction in flow area at a bridge) and; 3) local scour (caused by accelerated flow around piers and abutments). Total scour is the sum of the three components. Equations are available to compute depths for contraction and local scour and a summary of the results of these computations follows. There was no computed contraction scour for any modelled flow. Abutment scour ranged from 1.4 to 2.8 ft. The worst-case abutment scour occurred at the 500-year discharge. Additional information on scour depths and depths to armoring are included in the section titled “Scour Results”. Scoured-streambed elevations, based on the calculated scour depths, are presented in tables 1 and 2. A cross-section of the scour computed at the bridge is presented in figure 9. Scour depths were calculated assuming an infinite depth of erosive material and a homogeneous particle-size distribution. It is generally accepted that the Froehlich equation (abutment scour) gives “excessively conservative estimates of scour depths” (Richardson and others, 1995, p. 47). Usually, computed scour depths are evaluated in combination with other information including (but not limited to) historical performance during flood events, the geomorphic stability assessment, existing scour protection measures, and the results of the hydraulic analyses. Therefore, scour depths adopted by VTAOT may differ from the computed values documented herein.

Vermont↗

USGS1997

Level II scour analysis for Bridge 43 (SPRICYBRIG0043) on Bridge Street, crossing the Black River, Springfield, Vermont

This report provides the results of a detailed Level II analysis of scour potential at structure SPRICYBRIG0043 on Bridge Street crossing the Black River, Springfield, Vermont (figures 1–8). A Level II study is a basic engineering analysis of the site, including a quantitative analysis of stream stability and scour (U.S. Department of Transportation, 1993). Results of a Level I scour investigation also are included in Appendix E of this report. A Level I investigation provides a qualitative geomorphic characterization of the study site. Information on the bridge, gleaned from Vermont Agency of Transportation (VTAOT) files, was compiled prior to conducting Level I and Level II analyses and is found in Appendix D. The site is in the New England Upland section of the New England physiographic province in southeastern Vermont. The 191-mi 2 drainage area is a predominantly rural and forested basin. In the vicinity of the study site, the surface cover consist of some grass, buildings, and pavement. The immediate banks are covered with trees, shrubs and brush. In the study area, the Black River has an incised channel with a slope of approximately 0.001 ft/ft, an average channel top width of 156 ft and an average bank height of 14 ft. The channel bed material is predominantly cobbles with a median grain size (D 50 ) of 90.7 mm (0.298 ft). The geomorphic assessment at the time of the Level I and Level II site visit on September 19, 1996, indicated that the reach was stable. The Bridge Street crossing of the Black River is a 123-foot-long, two-lane bridge consisting of one 119-foot steel-beam span (Vermont Agency of Transportation, written communication, March 30, 1995). The bridge is supported by vertical, concrete abutments with wingwalls. The channel is skewed approximately 20 degrees to the opening while the opening-skew-to-roadway is 20 degrees. The scour protection measures at the site were type-2 stone fill (less than 36 inches diameter) along the downstream left bank and the downstream left wingwall. There was also type-1 stone fill (less than 12 inches diameter) along right abutment and the downstream right wingwall. There is a nine foot tall concrete wall along the downstream right bank to 89 feet downstream of the bridge. Additional details describing conditions at the site are included in the Level II Summary and Appendices D and E. Scour depths and recommended rock rip-rap sizes were computed using the general guidelines described in Hydraulic Engineering Circular 18 (Richardson and others, 1995). Total scour at a highway crossing is comprised of three components: 1) long-term streambed degradation; 2) contraction scour (due to accelerated flow caused by a reduction in flow area at a bridge) and; 3) local scour (caused by accelerated flow around piers and abutments). Total scour is the sum of the three components. Equations are available to compute depths for contraction and local scour and a summary of the results of these computations follows. There was no computed contraction scour. Left abutment scour ranged from 9.9 to 11 ft. The worst-case left abutment scour occurred at the 100-year discharge. Right abutment scour ranged from 6.5 to 11.2 ft. The worst-case right abutment scour occurred at the 500- year discharge. Additional information on scour depths and depths to armoring are included in the section titled “Scour Results”. Scoured-streambed elevations, based on the calculated scour depths, are presented in tables 1 and 2. A cross-section of the scour computed at the bridge is presented in figure 8. Scour depths were calculated assuming an infinite depth of erosive material and a homogeneous particle-size distribution. It is generally accepted that the Froehlich equation (abutment scour) gives “excessively conservative estimates of scour depths” (Richardson and others, 1995, p. 47). Usually, computed scour depths are evaluated in combination with other information including (but not limited to) historical performance during flood events, the geomorphic stability assessment, existing scour protection measures, and the results of the hydraulic analyses. Therefore, scour depths adopted by VTAOT may differ from the computed values documented herein.

Vermont↗

USGS1997

Level II scour analysis for Bridge 120 (LEICUS00070120) on U.S. Route 7, crossing the Leicester River, Leicester, Vermont

This report provides the results of a detailed Level II analysis of scour potential at structure LEICUS00070120 on U. S. Route 7 crossing the Leicester River, Leicester, Vermont (figures 1–8). A Level II study is a basic engineering analysis of the site, including a quantitative analysis of stream stability and scour (U.S. Department of Transportation, 1993). Results of a Level I scour investigation also are included in Appendix E of this report. A Level I investigation provides a qualitative geomorphic characterization of the study site. Information on the bridge, gleaned from Vermont Agency of Transportation (VTAOT) files, was compiled prior to conducting Level I and Level II analyses and is found in Appendix D. The site is in the Green Mountain section of the New England physiographic province in west-central Vermont. The 23.0-mi 2 drainage area is in a predominantly rural and forested basin. In the vicinity of the study site, the surface cover consists of shrubs, brush, and pasture with some trees except for the upstream left overbank area which is forest. In the study area, the Leicester River has a sinuous channel with a slope of approximately 0.002 ft/ft, an average channel top width of 52 ft and an average channel depth of 3 ft. The predominant channel bed material is sand and gravel with a median grain size (D 50 ) of 3.10 mm (0.0102 ft). The geomorphic assessment at the time of the Level I and Level II site visit on September 18, 1995, indicated that the reach was laterally unstable. Lateral instability was evident with the presence of some bank material failure and fallen or leaning vegetation at cut-banks upstream and downstream of this site. Point bars also were found near this site. The U. S. Route 7 crossing of the Leicester Riveris a 108-ft-long, two-lane bridge consisting of two 52-foot steel-beam spans (Vermont Agency of Transportation, written communication, March 13, 1995). The bridge is supported by vertical, concrete abutment walls with stone fill spill-through embankments on each abutment and one pier. The channel is skewed approximately 30 degrees to the opening while the opening-skew-toroadway is 15 degrees. The only scour protection measure at the site was type-3 stone fill (less than 48 inches diameter) on the spill-through embankments of each abutment. Additional details describing conditions at the site are included in the Level II Summary and Appendices D and E. Scour depths and rock rip-rap sizes were computed using the general guidelines described in Hydraulic Engineering Circular 18 (Richardson and others, 1995). Total scour at a highway crossing is comprised of three components: 1) long-term streambed degradation; 2) contraction scour (due to accelerated flow caused by a reduction in flow area at a bridge) and; 3) local scour (caused by accelerated flow around piers and abutments). Total scour is the sum of the three components. Equations are available to compute depths for contraction and local scour and a summary of the results of these computations follows. Contraction scour for all modelled flows ranged from 3.8 to 6.1 ft. The worst-case contraction scour occurred at the 500-year discharge. Abutment scour ranged from 4.0 to 6.7 ft. The worst-case abutment scour also occurred at the 500-year discharge. Pier scour ranged from 9.1 to 10.2. The worst-case pier scour occurred at the 500-year discharge. Additional information on scour depths and depths to armoring are included in the section titled “Scour Results”. Scoured-streambed elevations, based on the calculated scour depths, are presented in tables 1 and 2. A cross-section of the scour computed at the bridge is presented in figure 8. Scour depths were calculated assuming an infinite depth of erosive material and a homogeneous particle-size distribution. It is generally accepted that the Froehlich equation (abutment scour) gives “excessively conservative estimates of scour depths” (Richardson and others, 1995, p. 47). Usually, computed scour depths are evaluated in combination with other information including (but not limited to) historical performance during flood events, the geomorphic stability assessment, existing scour protection measures, and the results of the hydraulic analyses. Therefore, scour depths adopted by VTAOT may differ from the computed values documented herein.

Vermont↗

USGS1997

Level II scour analysis for Bridge 7H (HUNTTH0001007H) on Town Highway 1, crossing Cobb Brook, Huntington, Vermont

This report provides the results of a detailed Level II analysis of scour potential at structure HUNTTH001007H on Town Highway 1 crossing the Cobb Brook, Huntington, Vermont (figures 1–10). A Level II study is a basic engineering analysis of the site, including a quantitative analysis of stream stability and scour (U.S. Department of Transportation, 1993). Results of a Level I scour investigation also are included in Appendix E of this report. A Level I investigation provides a qualitative geomorphic characterization of the study site. Information on the bridge, gleaned from Vermont Agency of Transportation (VTAOT) files, was compiled prior to conducting Level I and Level II analyses and is found in Appendix D. In August 1976, Hurricane Belle caused flooding at this site which resulted in road and bridge damage (figures 7-8). This was approximately a 25-year flood event (U.S. Department of Housing and Urban Development, 1978). The site is in the Green Mountain section of the New England physiographic province in central Vermont. The 4.20-mi 2 drainage area is in a predominantly rural and forested basin. In the vicinity of the study site, the surface cover is forest upstream of the bridge. Downstream of the bridge is brushland and pasture. In the study area, the Cobb Brook has an incised, straight channel with a slope of approximately 0.03 ft/ft, an average channel top width of 43 ft and an average bank height of 6 ft. The channel bed material ranges from sand to boulders with a median grain size (D 50 ) of 65.5 mm (0.215 ft). The geomorphic assessment at the time of the Level I and Level II site visit on June 24, 1996, indicated that the reach was stable. The Town Highway 1 crossing of the Cobb Brook is a 23-ft-long, two-lane bridge consisting of one 20-foot concrete slab span (Vermont Agency of Transportation, written communication, June 21, 1996). The bridge is supported by vertical, concrete abutments with wingwalls. The channel is skewed approximately 15 degrees to the opening while the opening-skew-to-roadway is zero degrees. A scour hole 2.8 ft deeper than the mean thalweg depth was observed along the left abutment during the Level I assessment. Protection measures at the site include type-1 stone fill (less than 12 inches diameter) at the downstream right wingwall, type-2 stone fill (less than 36 inches diameter) at the upstream right wingwall and the downstream end of the downstream left wingwall, and type-3 stone fill (less than 48 inches diameter) at the upstream left wingwall. Additional details describing conditions at the site are included in the Level II Summary and Appendices D and E. Scour depths and recommended rock rip-rap sizes were computed using the general guidelines described in Hydraulic Engineering Circular 18 (Richardson and others, 1995). Total scour at a highway crossing is comprised of three components: 1) long-term streambed degradation; 2) contraction scour (due to accelerated flow caused by a reduction in flow area at a bridge) and; 3) local scour (caused by accelerated flow around piers and abutments). Total scour is the sum of the three components. Equations are available to compute depths for contraction and local scour and a summary of the results of these computations follows. Contraction scour for all modelled flows ranged from 0.2 to 1.3 ft. The worst-case contraction scour occurred at the incipient-overtopping discharge. Abutment scour ranged from 4.0 to 8.7 ft. The worst-case abutment scour occurred at the 500-year discharge. Additional information on scour depths and depths to armoring are included in the section titled “Scour Results”. Scoured-streambed elevations, based on the calculated scour depths, are presented in tables 1 and 2. A cross-section of the scour computed at the bridge is presented in figure 10. Scour depths were calculated assuming an infinite depth of erosive material and a homogeneous particle-size distribution. It is generally accepted that the Froehlich equation (abutment scour) gives “excessively conservative estimates of scour depths” (Richardson and others, 1995, p. 47). Usually, computed scour depths are evaluated in combination with other information including (but not limited to) historical performance during flood events, the geomorphic stability assessment, existing scour protection measures, and the results of the hydraulic analyses. Therefore, scour depths adopted by VTAOT may differ from the computed values documented herein.

Vermont↗

USGS1997

Level II scour analysis for Bridge 29 (HARDTH00310029) on Town Highway 31, crossing the Lamoille River, Hardwick, Vermont

This report provides the results of a detailed Level II analysis of scour potential at structure HARDTH00310029 on town highway 31 crossing the Lamoille River, Hardwick, Vermont (figures 1–8). A Level II study is a basic engineering analysis of the site, including a quantitative analysis of stream stability and scour (U.S. Department of Transportation, 1993). Results of a Level I scour investigation also are included in Appendix E of this report. A Level I investigation provides a qualitative geomorphic characterization of the study site. Information on the bridge, gleaned from Vermont Agency of Transportation (VTAOT) files, was compiled prior to conducting Level I and Level II analyses and is found in Appendix D. The site is in the New England Upland section of the New England physiographic province of north-central Vermont. The 64.4-mi 2 drainage area is in a predominantly rural basin. In the vicinity of the study site, the surface cover is pasture except for the immediate downstream channel banks and the downstream left overbank which are brush covered. In the study area, the Lamoille River has a sinuous channel with a slope of approximately 0.001 ft/ft, an average channel top width of 84 ft and an average channel depth of 4 ft. The predominant channel bed materials are cobble and gravel with a median grain size (D 50 ) of 36.1 mm (0.119 ft). The geomorphic assessment at the time of the Level I and Level II site visit on July 26, 1995, indicated that the reach was stable. The town highway 31 crossing of the Lamoille River is a 65-ft-long, one-lane bridge consisting of one 61-foot steel-beam span (Vermont Agency of Transportation, written communication, March 27, 1995). The bridge is supported by vertical, stone abutments with wingwalls. The right abutment has a concrete facing and a concrete subfooter. The channel is skewed approximately 5 degrees to the opening while the opening-skew-to-roadway is 0 degrees. Additional details describing conditions at the site are included in the Level II Summary and Appendices D and E. Scour depths and rock rip-rap sizes were computed using the general guidelines described in Hydraulic Engineering Circular 18 (Richardson and others, 1995). Total scour at a highway crossing is comprised of three components: 1) long-term streambed degradation; 2) contraction scour (due to accelerated flow caused by a reduction in flow area at a bridge) and; 3) local scour (caused by accelerated flow around piers and abutments). Total scour is the sum of the three components. Equations are available to compute depths for contraction and local scour and a summary of the results of these computations follows. Contraction scour for all modelled flows ranged from 0.0 to 2.7 ft. The worst-case contraction scour occurred at the 500-year discharge. Abutment scour ranged from 10.3 to 18.6 ft. The worst-case abutment scour occurred at the 100-year discharge at the right abutment. Additional information on scour depths and depths to armoring are included in the section titled “Scour Results”. Scoured-streambed elevations, based on the calculated scour depths, are presented in tables 1 and 2. A cross-section of the scour computed at the bridge is presented in figure 8. Scour depths were calculated assuming an infinite depth of erosive material and a homogeneous particle-size distribution. It is generally accepted that the Froehlich equation (abutment scour) gives “excessively conservative estimates of scour depths” (Richardson and others, 1995, p. 47). Usually, computed scour depths are evaluated in combination with other information including (but not limited to) historical performance during flood events, the geomorphic stability assessment, existing scour protection measures, and the results of the hydraulic analyses. Therefore, scour depths adopted by VTAOT may differ from the computed values documented herein.

Vermont↗