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USGS1996

Level II scour analysis for Bridge 32 (BRNATH00470032) 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 BRNATH00470032 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 of central Vermont in the town of Barnard. The 6.26-mi2 drainage area is in a predominantly rural and forested basin. In the vicinity of the study site, the banks have dense woody vegetation coverage except for the upstream right bank, which is grass and brush covered. In the study area, Locust Creek has an incised, sinuous channel with a slope of approximately 0.029 ft/ft, an average channel top width of 44 ft., and an average channel depth of 5 ft. The predominant channel bed material is gravel and cobbles (D50 is 91.7 mm or 0.301 ft). The geomorphic assessment at the time of the Level I and Level II site visit on October 12, 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 span concrete slab superstructure (Vermont Agency of Transportation, written commun., August 23, 1994). The bridge is supported by vertical, concrete abutments with concrete wingwalls. The channel is skewed approximately 10 degrees to the opening while the opening-skew-to-roadway is 35 degrees. The scour protection measures at the site were type-2 stone fill (less than 36 inches diameter) on the banks upstream, the upstream wingwalls, the downstream right wingwall, and the downstream right bank. The downstream left wingwall and left bank are protected with type-3 stone fill (less than 48 inches diameter). 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, 1993). 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 these computed results follow. Contraction scour for all modelled flows ranged from 1.4 to 2.2 feet. The worst-case contraction scour occurred at the 500-year discharge. Abutment scour ranged from 10.3 to 15.0 feet. 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 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, 1993, 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↗
USGS1996

Level II scour analysis for Bridge 15 (GRNVTH00230015) on Town Highway 23, crossing the Third Branch of the White River, Granville, Vermont

This report provides the results of a detailed Level II analysis of scour potential at structure GRNVTH00230015 on town highway 23 crossing the Third Branch of the White River, Granville, 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 study is included in Appendix E of this report. 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 can be found in Appendix D. The site is in the Green Mountain physiographic province of central Vermont in the town of Granville. The 23.6-mi 2 drainage area is in a predominantly rural and forested basin. In the vicinity of the study site, the banks have woody vegetation coverage except for the downstream banks, which are residential. In the study area, the Third Branch of the White River has an incised, sinuous channel with a slope of approximately 0.0128 ft/ft, an average channel top width of 42 ft and an average channel depth of 4 ft. The predominant channel bed material is cobble (D 50 is 108 mm or 0.353 ft). The geomorphic assessment at the time of the Level I and Level II site visit on October 21, 1994, indicated that the reach was laterally unstable. The town highway 23 crossing of the Third Branch of the White River is a 35-ft-long, one-lane bridge consisting of one 31-foot steel beam span (Vermont Agency of Transportation, written communication, August 26, 1994). 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 10 degrees. The only scour protection measures in place at the site were type-1 stone fill (less than 12 inches diameter) along the upstream right bank, upstream right wingwall, and right abutment. Retaining walls are in place along the upstream left bank up to the upstream end of the upstream left wingwall and both downstream banks with the left bank wall extending from the downstream left wingwall. 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 scour 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 to 0.4 ft. The worst-case contraction scour occurred at the incipient overtopping discharge. Abutment scour ranged from 9.8 to 13.9 ft. The worst-case abutment scour occurred at the 100-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 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 53 (CHESTH01180053) on Town Highway 118, crossing the Williams River, Chester, Vermont

This report provides the results of a detailed Level II analysis of scour potential at structure CHESTH01180053 on Town Highway 118 crossing the Williams River, Chester, 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 20.8-mi 2 drainage area is in a predominantly rural and forested basin. In the vicinity of the study site, the surface cover is predominantly suburban while the right bank upstream is pasture. There is a house on the right bank downstream and VT 103 runs parallel to the river along the left bank. In the study area, the Williams River has an incised, straight channel with a slope of approximately 0.005 ft/ft, an average channel top width of 64 ft and an average bank height of 7 ft. The channel bed material ranges from sand to boulder with a median grain size (D 50 ) of 58.0 mm (0.190 ft). The geomorphic assessment at the time of the Level I and Level II site visit on September 17, 1996, indicated that the reach was stable. The Town Highway 118 crossing of the Williams River is a 43-ft-long, one-lane bridge consisting of one 40-foot steel-beam span (Vermont Agency of Transportation, written communication, April 6, 1995). The opening length of the structure parallel to the bridge face is 37.6 ft. The bridge is supported by vertical, concrete abutments with wingwalls. The channel is skewed approximately 5 degrees to the opening while the computed opening-skew-to-roadway is 10 degrees. A scour hole 0.5 ft deeper than the mean thalweg depth was observed at both abutments during the Level I assessment. Scour protection measures at the site include: type-3 stone fill (less than 48 inches diameter) along the left bank upstream and downstream and type-2 stone fill (less than 36 inches diameter) along the entire base length of the upstream left wingwall, at the upstream end of the left abutment, and at the upstream end of the downstream 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) for the 100- and 500-year discharges. In addition, the incipient roadway-overtopping discharge is determined and analyzed as another potential worst-case scour scenario. 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 5.8 to 6.8 ft at the left abutment and 9.4 to 14.4 ft at the right abutment. The worst-case abutment scour occurred 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 31 (JERITH00350031) on Town Highway 35, crossing Mill Brook, Jericho, Vermont

This report provides the results of a detailed Level II analysis of scour potential at structure JERITH00350031 on Town Highway 35 crossing Mill Brook, Jericho, 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, gathered 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 and the Champlain section of the St. Lawrence physiographic province in northwestern Vermont. The 15.7-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. The downstream left overbank is pasture. The downstream right overbank is brushland. In the study area, the Mill Brook has an incised, sinuous channel with a slope of approximately 0.02 ft/ft, an average channel top width of 117 ft and an average bank height of 11 ft. The channel bed material ranges from gravel to boulders with a median grain size (D 50 ) of 81.1 mm (0.266 ft). The geomorphic assessment at the time of the Level I and Level II site visit on July 3, 1996, indicated that the reach was laterally unstable. The Town Highway 35 crossing of the Mill Brook is a 53-ft-long, one-lane bridge consisting of a 50-foot steel-beam span with a wooden deck (Vermont Agency of Transportation, written communication, November 30, 1995). The opening length of the structure parallel to the bridge face is 48 ft. The bridge is supported by a vertical, concrete abutment with wingwalls on the left. On the right, the abutment and wingwalls are laid-up stone with a concrete cap. The channel is not skewed to the opening. The roadway is skewed 10 degrees to the opening. A scour hole 1.5 ft deeper than the mean thalweg depth was observed along the left abutment during the Level I assessment. Scour countermeasures at the site were type-2 stone fill (less than 36 inches diameter) at the upstream and downstream left wingwalls, the upstream and downsteam left channel banks, and the downstream left road embankment. 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). In addition, the incipient roadway-overtopping discharge is analyzed since it has the potential of being the worst-case scour scenario. 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 1.3 ft. The worst-case contraction scour occurred at the 500-year discharge. Left abutment scour ranged from 9.9 to 12.4 ft. Right abutment scour ranged from 13.8 to 17.8 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 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↗
USGS1996

Level II scour analysis for Bridge 42 (BETHTH00860042) on Town Highway 86, crossing Gilead Brook, Bethel, Vermont

This report provides the results of a detailed Level II analysis of scour potential at structure BETHTH00860042 on town highway 86 crossing Gilead Brook, Bethel, 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 study is included in Appendix E of this report. A Level I study provides a qualitative geomorphic characterization of the study site. Information on the bridge available from VTAOT files were compiled prior to conducting Level I and Level II analyses and can be found in Appendix D. The site is in the Green Mountain physiographic province of central Vermont in the town of Bethel. The 11.4-mi 2 drainage area is in a predominantly rural and forested basin. In the vicinity of the study site, the upstream banks are tree covered and the downstream banks are covered with shrubs and brush. In the study area, Gilead Brook is probably incised, has a sinuous channel with a slope of approximately 0.012 ft/ft, an average channel top width of 53 ft, and an average channel depth of 5 ft. The predominant channel bed material is gravel to cobbles (D 50 is 85.6 mm or 0.281 ft). The geomorphic assessment at the time of the Level I and Level II site visit on September 30, 1994, indicated that the reach was stable. The town highway 86 crossing of Gilead Brook is a 28-ft-long, one-lane bridge consisting of one 25-foot clear-span structure with a concrete deck (Vermont Agency of Transportation, written commun., August 24, 1994). The bridge is supported by concrete abutments with wingwalls. The bridge skew is approximately 5 degrees and there is no opening-skew-to-roadway. A scour hole approximately 1 ft deeper than the mean thalweg depth was observed along the left bank, near the upstream bridge face during the Level I assessment. There is also approximately 1 ft of scour along the left abutment of the bridge, near the upstream wing wall, exposing the footing. There is type-one (less than 12 in diameter) protection on the US left wingwall and type-two (less than 36 in diameter) along the US and DS right wingwalls. There is no protection along the abutments. 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 to 1.9 ft. The worst-case contraction scour occurred at the incipient-overtopping discharge and the 100-year discharge. Abutment scour ranged from 8.6 to 15.7 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). Many factors, including historical performance during flood events, the geomorphic assessment, scour protection, and the results of the hydraulic analyses, must be considered to properly assess the validity of abutment scour results. Therefore, scour depths adopted by VTAOT may differ from the computed values documented herein, based on the consideration of additional contributing factors and engineering judgement.

Vermont↗
USGS1996

Level II scour analysis for Bridge 13 (POMFTH00020013) on Town Highway 2, crossing Barnard Brook, Pomfret, Vermont

This report provides the results of a detailed Level II analysis of scour potential at structure POMFTH00020013 on town highway 2 crossing Barnard 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 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 can be found in Appendix D. The site is in the New England Upland section of the New England physiographic province of east-central Vermont in the town of Pomfret. The 7.98-mi 2 drainage area is in a predominantly rural and forested basin. In the vicinity of the study site, the surface cover is primarily field grasses with some brush on the immediate banks. In the study area, Barnard Brook has an incised, sinuous channel with a slope of approximately 0.006 ft/ft, an average channel top width of 32 ft and an average channel depth of 4 ft. The predominant channel bed materials are gravel and cobbles with a median grain size (D 50 ) of 51.0 mm (0.167 ft). The geomorphic assessment at the time of the Level I and Level II site visit on September 15, 1994, indicated that the reach was stable. The town highway 2 crossing of Barnard Brook is a 23-ft-long, two-lane bridge consisting of one 20-foot concrete span (Vermont Agency of Transportation, written communication, August 22, 1994). The bridge is supported by vertical, concrete abutments with wingwalls. The channel is skewed approximately 30 degrees to the opening while the opening-skew-toroadway is 0 degrees. Scour, 2.5 ft deeper than the mean thalweg depth, was observed along the left abutment 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 base and upstream of 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 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 1.5 ft. The worst-case contraction scour occurred at the 100-year discharge. Abutment scour ranged from 7.2 to 12.6 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 63 (CHESTH00090063) on Town Highway 9, crossing the Williams River, Chester, Vermont

This report provides the results of a detailed Level II analysis of scour potential at structure CHESTH00090063 on Town Highway 9 crossing the Williams River, Chester, 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 eastern Vermont. The 24.0-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 trees and brush along the immediate banks. In the study area, the the Williams River has an incised, sinuous channel with a slope of approximately 0.005 ft/ft, an average channel top width of 64 ft and an average bank height of 6 ft. The channel bed material ranges from gravel to boulder with a median grain size (D 50 ) of 57.7 mm (0.189 ft). The geomorphic assessment at the time of the Level I and Level II site visit on September 18, 1996, indicated that the reach was stable. The Town Highway 9 crossing of the Williams River is a 45-ft-long, two-lane bridge consisting of one 35-foot steel-beam span with a timber deck (Vermont Agency of Transportation, written communication, April 6, 1995). The bridge is supported by vertical, concrete abutments with wingwalls. The channel is skewed approximately 5 degrees to the opening while the opening-skew-to-roadway is 0 degrees. A scour hole 1.8 ft deeper than the mean thalweg depth was observed along the left abutment during the Level I assessment. The scour hole undermines the left abutment and extends from 50 ft upstream of the upstream bridge face to 50 ft downstream of the downstream bridge face. The scour protection measures at the site included type-3 stone fill (less than 48 inches diameter) under the bridge along the entire base length of the right abutment and along the right bank from 50 to 88 ft upstream. Type-2 (less than 36 inches diameter) stone fill scour protection was observed along the downstream left bank from 18 ft to 115 ft, along the downstream right bank from 8 ft to 25 ft and along the upstream left bank from 50 to 75 ft. 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 was computed to be 0.0 ft. Abutment scour ranged from 10.1 ft to 11.0 ft along the left abutment and from 14.1 ft to 15.1 ft along the right abutment. The worst-case abutment scour for the left abutment occurred at the 500-year discharge while the worst-case abutment scour for the right abutment occurred at the 100- 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 34 (ROCHTH00210034) on Town Highway 21, crossing the White River, Rochester, Vermont

This report provides the results of a detailed Level II analysis of scour potential at structure ROCHTH00210034 on Town Highway 21 crossing the White River, Rochester, 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, obtained 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 74.8-mi 2 drainage area is in a predominantly rural and forested basin. In the vicinity of the study site, the surface cover is suburban on the upstream and downstream left overbanks, though brush prevails along the immediate banks. On the upstream and downstream right overbanks, the surface cover is pasture with brush and trees along the immediate banks. In the study area, the White River has an incised, straight channel with a slope of approximately 0.002 ft/ft, an average channel top width of 102 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 74.4 mm (0.244 ft). The geomorphic assessment at the time of the Level I and Level II site visit on July 23, 1996, indicated that the reach was stable. The Town Highway 21 crossing of the White River is a 72-ft-long, two-lane bridge consisting of 70-foot steel stringer span (Vermont Agency of Transportation, written communication, March 22, 1995). The opening length of the structure parallel to the bridge face is 67.0 ft. 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. Channel scour, 1.5 ft deeper than the mean thalweg depth was observed along the left abutment and wingwalls during the Level I assessment. Scour countermeasures at the site includes type-1 stone fill (less than 12 inches diameter) along the upstream left bank and the upstream and downstream left road embankments, type-2 (less than 36 inches diameter) along the upstream end of the upstream left wingwall and downstream left bank, and type-3 (less than 48 inches diameter) along the downstream end of the downstream 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). In addition, the incipient roadway-overtopping discharge is analyzed since it has the potential of being the worst-case scour scenario. 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 discharges was zero. Left abutment scour ranged from 6.8 to 21.2 ft. Right abutment scour ranged from 13.9 to 18.4 ft. The worst-case abutment scour occurred at the 500-year discharge at the left and right abutments. 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↗
USGS1996

Level II scour analysis for Bridge 40 (BETHTH00230040) on Town Highway 23, crossing Gilead Brook, Bethel, Vermont

This report provides the results of a detailed Level II analysis of scour potential at structure BETHTH00230040 on town highway 23 crossing Gilead Brook, Bethel, 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 study is included in Appendix E of this report. A Level I study provides a qualitative geomorphic characterization of the study site. Information on the bridge, gleaned from VTAOT files, was compiled prior to conducting the Level I and Level II analyses and can be found in Appendix D. The site is in the Green Mountain physiographic province of central Vermont in the town of Bethel. The 10.2-mi 2 drainage area is in a predominantly rural and forested basin. In the vicinity of the study site, the banks have moderately dense woody vegetation coverage. In the study area, the Gilead Brook has an incised, sinuous channel downstream of the site and a meandering channel upstream, with narrow flood plains and a slope of approximately 0.015 ft/ft, an average channel top width of 47.0 ft and an average channel depth of 2.75 ft. The predominant channel bed materials are gravel and cobble (D 50 is 94.8 mm or 0.311 ft). The geomorphic assessment at the time of the Level I and Level II site visit on October 14, 1994, indicated that the reach was laterally unstable. The town highway 23 crossing of Gilead Brook is a 37-ft-long, one-lane bridge consisting of one 34-foot span steel-stringer type superstructure (Vermont Agency of Transportation, written commun., August 24, 1994). The bridge is supported by vertical, concrete abutments with concrete wingwalls. The channel is skewed 25 degrees to the opening and the opening-skew-to-roadway is zero degrees. A scour hole 1.0 ft deeper than the mean thalweg depth was observed along the downstream right wingwall 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 and downstream right roadway embankments, at the extreme upstream and downstream ends of the upstream and downstream right wingwalls, and along the entire base length of the downstream left wingwall. 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, 1993). Scour depths were calculated assuming an infinite depth of erosive material and a homogeneous particle-size distribution. The scour analysis results are presented in tables 1 and 2 and a graph of the scour depths is presented in figure 8.

Vermont↗
USGS1997

Level II scour analysis for Bridge 7 (MORRTH00020007) on Town Highway 2 (FAS 239), crossing Ryder Brook, Morristown, Vermont

This report provides the results of a detailed Level II analysis of scour potential at structure MORRTH00020007 on Town Highway 2 crossing Ryder Brook, Morristown, 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 North-central Vermont. The 18.5-mi 2 drainage area is in a predominantly rural and forested basin. In the vicinity of the study site, the surface cover is pasture and forest. In the study area, Ryder Brook generally is straight and incised with a slope of approximately 0.002 ft/ft, an average channel top width of 48 ft and an average channel depth of 3 ft. The channel bed is bedrock with pockets of sand and gravel in several locations through the reach. The gravel has a median grain size (D 50 ) of 17.7 mm (0.0581 ft). The geomorphic assessment at the time of the Level I and Level II site visit on July 16, 1996 indicated that the reach was stable. The Town Highway 2 crossing of Ryder Brook is a 84-ft-long, two-lane bridge consisting of one 84-foot steel-beam span (Vermont Agency of Transportation, written communication, January 31, 1996). The bridge is supported by vertical, concrete abutment walls with spill-through embankments. The channel is skewed approximately 10 degrees to the opening while the opening-skew-to-roadway 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 predictions for all modelled flows at this site were zero. Abutment scour predictions ranged from 5.6 to 8.1 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. However, historical bridge records and field notes indicate the abutment footings may be set on bedrock. 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 22 (WALDTH00180022) on Town Highway 18, crossing Coles Brook, Walden, Vermont

This report provides the results of a detailed Level II analysis of scour potential at structure WALDTH00180022 on Town Highway 18 crossing Coles Brook also known as Joes Brook, Walden, 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 northeastern Vermont. The 12.5-mi 2 drainage area is in a predominantly rural and forested basin. In the vicinity of the study site, the surface cover is predominantly forested while the downstream left bank is shrub and brushland. In the study area, the Coles Brook has an incised, sinuous channel with a slope of approximately 0.004 ft/ft, an average channel top width of 54 ft and an average bank height of 4 ft. The channel bed material ranges from gravel to bedrock with a median grain size (D50) of 124.1 mm (0.407 ft). The D 50 was taken from a pebble count in the downstream channel, because the upstream channel is primarily bedrock. The geomorphic assessment at the time of the Level I and Level II site visit on August 8, 1995, indicated that the reach was stable. The Town Highway 18 crossing of the Coles Brook is a 46-ft-long, one-lane bridge consisting of one 44-foot steel-beam span with a wooden deck (Vermont Agency of Transportation, written communication, April 5, 1995). The opening length of the structure parallel to the bridge face is 41.4 ft. The bridge is supported by a vertical, concrete abutment with wingwalls on the left and by a vertical, stone abutment with stone wingwalls with a concrete cap on the right. The channel is skewed approximately 5 degrees to the opening while the computed opening-skew-to-roadway is 10 degrees. The only scour protection measure at the site was a stone wall along the upstream left bank and type-2 stone fill (less than 36 inches diameter) along the entire base length of the upstream left wingwall, left abutment, and downstream left wing wall. 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) for the 100-year and 500-year discharges. 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 6.4 to 7.9 ft at the left abutment and from 11.8 to 14.9 ft at the right 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”. Scouredstreambed 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 particlesize 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 25 (REDSTH00360025) on Town Highway 36, crossing the West Branch Deerfield River, Readsboro, Vermont

This report provides the results of a detailed Level II analysis of scour potential at structure REDSTH00360025 on Town Highway 36 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 south-central Vermont. The 14.5-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 right bank and forest on the upstream left bank. The surface cover on the downstream right and left banks is primarily grass, shrubs and brush. In the study area, the West Branch Deerfield River has an incised, sinuous channel with a slope of approximately 0.02 ft/ft, an average channel top width of 65 ft and an average bank height of 4 ft. The channel bed material ranges from gravel to boulders, with a median grain size (D 50 ) of 117 mm (0.383 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 stable. The Town Highway 36 crossing of the West Branch Deerfield River is a 59-ft-long, two-lane bridge consisting of one 57-foot concrete T-beam span (Vermont Agency of Transportation, written communication, September 28, 1995). The opening length of the structure parallel to the bridge face is 54 ft. The bridge is supported by vertical, concrete abutments with wingwalls. The channel is skewed approximately 50 degrees to the opening while the opening-skew-to-roadway is 30 degrees. During the Level I assessment, a scour hole approximately 2 ft deeper than the mean thalweg depth was observed along the upstream right wingwall and a scour hole approximately 1 ft deeper than the mean thalweg depth was observed along the downstream left wingwall. The scour protection measure at the site was type-2 stone fill (less than 36 inches diameter) at the downstream end of the downstream left wingwall, at the upstream end of the upstream right wingwall, at the downstream end of the right abutment, along the entire base length of the downstream right wingwall, along the upstream right bank and along the downstream left bank. A stone wall was noted 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 0.0 to 0.6 ft. The worst-case contraction scour occurred at the incipient-overtopping discharge. Abutment scour ranged from 15.1 to 16.3 ft along the left abutment and from 7.4 to 9.2 ft along the right abutment. The worst-case abutment scour occurred at the incipient-overtopping and 500-year discharges for the left abutment and at the 500-year discharge for 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↗
USGS2002

Topographic map of Mars M 25M RKN

NOTES ON BASE This map is based on data from the Mars Orbiter Laser Altimeter (MOLA) (Smith and others, 2001), an instrument on NASA's Mars Global Surveyor (MGS) spacecraft (Albee and others, 2001). The image used for the base of this map represents more than 600 million measurements gathered between 1999 and 2001, adjusted for consistency (Neumann and others, 2001, 2002) and converted to planetary radii. These have been converted to elevations above the areoid as determined from a martian gravity field solution GMM2 (Lemoine and others, 2001), truncated to degree and order 50, and oriented according to current standards (see below). The average accuracy of each point is originally ~100 meters in horizontal position, and ~1 meter in radius (Neumann, 2001). However, the total elevation uncertainty is at least +3 m due to the global error in the areoid (+1.8 meters according to Lemoine and others, 2001) and regional uncertainties in its shape (communication from Neumann, 2002). The measurements were converted into a digital elevation model (DEM) (communication from Neumann, 2002; Neumann and others, 2001; Smith and others, 2001) using Generic Mapping Tools software (Wessel and Smith, 1998), with a resolution of 0.015625 degrees per pixel or 64 pixels per degree. In projection, the pixels are 926.17 meters in size at the equator. PROJECTION The Mercator projection is used between latitudes +57°, with a central meridian at 0° and latitude equal to the nominal scale at 0°. The Polar Stereographic projection is used for the polar regions north of the +55° parallel and south of the –55° parallel with a central meridian set for both at 0°. The adopted equatorial radius is 3,396.19 km (Duxbury and others 2002; Seidelmann and others 2002). COORDINATE SYSTEM The MOLA data were initially referenced to an internally consistent inertial coordinate system, derived from tracking of the MGS spacecraft. By adopting appropriate values for the orientation of Mars as defined by the International Astronomical Union (IAU) and the International Association of Geodesy (IAG) (Seidelmann and others, 2002), these inertial coordinates were converted into the planet-fixed coordinates (longitude and latitude) used on this map. These values include the orientation of the north pole of Mars (including the effects of precession), the rotation rate of Mars, and a value for W0 of 176.630°, where W0 is the angle along the equator to the east, between the 0° meridian and the equator's intersection with the celestial equator at the standard epoch J2000.0 (Seidelmann and others, 2002). This value of W0 was chosen (Duxbury and others, 2002) in order to place the 0° meridian through the center of the small (~500 m) crater Airy-0, located in the crater Airy (de Vaucouleurs and others, 1973; Seidelmann and others, 2002). Longitude increases to the east, and latitude is planetocentric as allowed by IAU/IAG standards (Seidelmann and others, 2002) and in accordance with current NASA and USGS standards (Duxbury and others, 2002). A secondary grid (printed in red) has been added to the map as a reference to the west longitude/planetographic latitude system that is also allowed by IAU/IAG standards (Seidelmann and others, 2002) and has also been used for Mars. The figure adopted to compute this secondary grid is an oblate spheroid with an equatorial radius of 3,396.19 km and a polar radius of 3,376.2 km (Duxbury and others, 2002; Seidelmann and others, 2002). MAPPING TECHNIQUES To create the topographic base image, the original DEM produced by the MOLA team in Simple Cylindrical projection with a resolution of 64 pixels per degree was projected into the Mercator and Polar Stereographic pieces. A shaded relief was generated from each DEM with a sun angle of 30° from horizontal and a sun azimuth of 270°, as measured clockwise from north, and a vertical exaggeration of 100%. Illumination is from the west, which follows a long-standing USGS tradition for planetary maps. This allows for continuity in the shading between maps and quadrangles, and most closely resembles lighting conditions found on imagery. The DEM values were then mapped to a smooth global color look-up table. Note that the chosen color scheme simply represents elevation changes and is not intended to imply anything about surface characteristics (e.g., past or current presence of water or ice). These two files were then merged and scaled to 1:25 million for the Mercator portion and 1:15,196,708 for the two Polar Stereographic portions, with a resolution of 300 dots per inch. The projections have a common scale of 1:13,923,113 at +56° latitude. NOMENCLATURE Names on this sheet are approved by the IAU and have been applied for features clearly visible at the scale of this map. For a complete list of the IAU-approved nomenclature for Mars, see the Gazetteer of Planetary Nomenclature at http://planetarynames.wr.usgs.gov/. Font color was chosen for readability. Names followed by an asterisk are provisionally approved. *M 25M RKN: Abbreviation for Mars, 1:25,000,000 series, shaded relief (R), with color (K) and nomenclature (N) (Greeley and Batson, 1990)

Open-File Report↗
USGS1994

Hydrologic data for the alluvium and terrace deposits of the Cimarron River from Freedom to Guthrie, Oklahoma

Ground water in the Quaternary alluvium and terrace deposits associated with the Cimarron River in northwestern Oklahoma is used extensively for irrigation, municipal, stock, and domestic supplies. The data in this report were collected as part of an investigation to provide State water managers with the quantitative knowledge necessary to manage the ground-water resource effectively. The investigation was conducted by the U.S. Geological Survey in cooperation with the Oklahoma Geological Survey. The information presented in this report include data collected in the field from 1985 through 1989, and unpublished data compiled from files of the U.S. Geological Survey and the Oklahoma Water Resources Board. Data include well and test-bole records, consisting of ground-water levels, depth of wells, principal aquifer, and primary use of water. Water levels include continuous, daily, monthly, and periodic measure- ments for selected wells. Concentrations of common chemical constituents, selected trace elements, organic analyses, and tritium analyses of water samples from wells completed in the Cimarron River alluvium and terrace deposits and Permian geologic units are reported. Winter and summer base-flow discharge measurements of the Cimarron River and its Tributaries are presented together with water-quality data from the measuring sites. Continuous water-level and precipitation-gage data are presented graphically. Locations of data- collection sites are shown on plates.

Open-File Report↗
USGS1996

Level II scour analysis for Bridge 14 (FFIETH00010014) on Town Highway 1, crossing the Fairfield River, Fairfield, Vermont

This report provides the results of a detailed Level II analysis of scour potential at structure FFIETH00010014 on Town Highway 1 crossing the Fairfield River, Fairfield, 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 northwestern Vermont. The 7.84-mi 2 drainage area is in a predominantly rural and forested basin. In the vicinity of the study site, the surface cover on the upstream left and downstream right is row crops. The surface cover on the upstream right and downstream left is pasture. In the study area, the Fairfield River has a sinuous channel with a slope of approximately 0.006 ft/ft, an average channel top width of 33 ft and an average channel depth of 3 ft. The channel bed material ranges from silt to gravel with a median grain size (D 50 ) of 15.4 mm (0.0505 ft). The geomorphic assessment at the time of the Level I and Level II site visit on July 11, 1995, indicated that the reach was laterally unstable. The Town Highway 1 crossing of the Fairfield River is a 26-ft-long, two-lane bridge consisting of one 23-foot concrete span (Vermont Agency of Transportation, written communication, March 9, 1995). The bridge is supported by vertical, concrete abutments with wingwalls. The channel is skewed approximately 27 degrees to the opening while there is no opening-skew-to-roadway. The bridge is located on a sharp channel bend. Th e left abutment is impacted due to this bend. A scour hole 1.5 ft deeper than the mean thalweg depth was observed along the left abutment during the Level I asse ssment. Scour protection measures at the site include type- 3 stone fill (less than 48 inches diameter ) along the immediate upstream banks and along the base of the upstream left wi ngwall. Type-2 stone fill (le ss than 36 inches diameter) was present along the downstream left wingwall. A dditional 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 5.4 to 8.0 ft. The worst-case contraction scour occurred at the 500-year discharge. Abutment scour ranged from 3.0 to 8.3 ft. The worst-case abutment scour also occurred at the 500-year discharge. Additional information on scour depths and depths to armoring are include d 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 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 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.

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