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At least 1,369 records · Page 76Linked to original sources
USGS1997

Level II scour analysis for Bridge 10 (WFIETH00170010) on Town Highway 17, crossing Taft Brook, Westfield, Vermont

This report provides the results of a detailed Level II analysis of scour potential at structure WFIETH00170010 on Town Highway 17 crossing Taft Brook, Westfield, 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 northern Vermont. The 2.39-mi 2 drainage area is in a predominantly rural and forested basin. In the vicinity of the study site, the immediate channel banks have thick woody vegetation while the overbanks are grass or pasture. In the study area, Taft Brook has an incised, sinuous channel with a slope of approximately 0.04 ft/ft, an average channel top width of 38 ft and an average bank height of 6 ft. The predominant channel bed material is cobble with a median grain size (D 50 ) of 85.3 mm (0.280 ft). The geomorphic assessment at the time of the Level I and Level II site visit on June 26, 1995, indicated that the reach was stable. The Town Highway 17 crossing of Taft Brook is a 26-ft-long, two-lane bridge consisting of one 24-foot concrete span (Vermont Agency of Transportation, written communication, March 7, 1995). The opening length of the structure parallel to the bridge face is 23.1 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 25 degrees. There is 0.1 ft (vertical) undermining of both abutments and 0.8 feet of undermining at the downstream right wingwall. Scour countermeasures at the site include sparsely placed type- 2 stone fill (less than 36 inches diameter) at the ends of each wingwall. Additional details describing conditions at the site are included in the Level II Summary and Appendices D and E. There is 0.1 ft (vertical) undermining of both abutments and 0.8 feet of undermining at the downstream right wingwall. Scour countermeasures at the site include sparsely placed type- 2 stone fill (less than 36 inches diameter) at the ends of each 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 0.1 to 0.4 ft. The worst-case contraction scour occurred at the 500-year discharge. Abutment scour at the left abutment ranged from 6.1 to 7.7 ft. Abutment scour at the right abutment ranged from 4.3 to 5.4 ft.The worst-case abutment scour occurred at the 500-year discharge for both 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↗
USGS1997

Level II scour analysis for Bridge 6 (ALBUTH00150006) on Town Highway 15, crossing Mud Creek, Alburg, Vermont

This report provides the results of a detailed Level II analysis of scour potential at structure ALBUTH00150006 on Town Highway 15 crossing Mud Creek, Alburg, 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 Champlain section of the St. Lawrence Valley physiographic province in northwestern Vermont. The 2.90-mi 2 drainage area is in a predominantly rural and forested basin. However, nearly a third of the drainage, including the location of the study site, is wetland. In the study area, Mud Creek has an sinuous channel through wetland with a slope of approximately 0.0002 ft/ft, an average channel top width of 42 ft and an average bank height of 2 ft. The channel bed material ranges from clay to sand with an estimated median grain size (D 50 ) of 0.047 mm (0.00015 ft). The geomorphic assessment at the time of the Level I and Level II site visit on June 26, 1995, indicated that the reach was stable. The Town Highway 15 crossing of Mud Creek is a 30-ft-long, one-lane bridge consisting of one 28-foot steel-beam span (Vermont Agency of Transportation, written communication, March 7, 1995). The opening length of the structure parallel to the bridge face is 26.7 ft. The bridge is supported by vertical, concrete abutments with wingwalls. The channel is skewed zero degrees to the opening and the opening-skew-to-roadway is also zero degrees. Channel scour, approximately 2 ft deeper than the mean thalweg depth, was observed in the middle of the channel extending from 5 to 35 ft upstream of the bridge. The only scour countermeasure observed at this site was some small stone, possibly type-1 stone fill (less than 12 inches diameter), partially covering the channel bed under 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. Contraction scour for all modelled flows ranged from 6.2 to 7.2 ft. The worst-case contraction scour occurred at the 500-year discharge. Abutment scour ranged from 2.0 to 2.4 ft and 2.1 to 2.6 ft on the left and right abutments respectively. 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 crosssection 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. 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 37 (DUXBTH00120037) on Town Highway 12, crossing Ridley Brook, Duxbury, Vermont

This report provides the results of a detailed Level II analysis of scour potential at structure DUXBTH00120037 on Town Highway 12 crossing Ridley Brook, Duxbury, 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 10.1-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 and downstream of the bridge. In the study area, Ridley Brook has an incised, straight channel with a slope of approximately 0.04 ft/ft, an average channel top width of 67 ft and an average bank height of 9 ft. The channel bed material ranges from gravel to boulders with a median grain size (D 50 ) of 123 mm (0.404 ft). The geomorphic assessment at the time of the Level I and Level II site visit on July 1, 1996, indicated that the reach was stable. The Town Highway 12 crossing of Ridley Brook is a 33-ft-long, two-lane bridge consisting of five 30-ft steel rolled beams (Vermont Agency of Transportation, written communication, October 13, 1995). The opening length of the structure parallel to the bridge face is 30 ft. The bridge is supported by vertical, concrete abutments with wingwalls. The channel is skewed approximately 50 degrees to the opening while the measured opening-skew-to-roadway is 20 degrees. A scour hole 2 ft deeper than the mean thalweg depth was observed along the right abutment and downstream right wingwall during the Level I assessment. Scour countermeasures at the site include type-2 stone fill (less than 3 feet diameter) along the upstream and downstream left road embankments, and type-3 stone fill (less than 4 feet diameter) along the upstream right bank and upstream 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 0.6 to 1.7 ft. The worst-case contraction scour occurred at the 500-year discharge. Left abutment scour ranged from 5.0 to 8.3 ft, with the worst-case occurring at the incipient-overtopping discharge. Right abutment scour ranged from 13.1 to 16.7 ft, with the worst-case occurring 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 44 (LINCTH00330044) on Town Highway 33, crossing the New Haven River, Lincoln, Vermont

This report provides the results of a detailed Level II analysis of scour potential at structure LINCTH00330044 on Town Highway 33 crossing the New Haven River, Lincoln, 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 6.3-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 New Haven River has an incised, sinuous channel with a slope of approximately 0.02 ft/ft, an average channel top width of 56 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 101.9 mm (0.334 ft). The geomorphic assessment at the time of the Level I and Level II site visit on June 10, 1996, indicated that the reach was stable. The Town Highway 33 crossing of the New Haven River is a 33-ft-long, one-lane bridge consisting of one 31-foot timber-beam span (Vermont Agency of Transportation, written communication, December 14, 1995). The opening length of the structure parallel to the bridge face is 29.3 ft. The bridge is supported by vertical, wood-beam crib abutments with wingwalls. The channel is skewed approximately 25 degrees to the opening while the opening-skew-to-roadway is zero degrees. A scour hole 1.0 ft deeper than the mean thalweg depth was observed along the right abutment during the Level I assessment. The scour protection measures at the site included type-1 stone fill (less than 12 inches diameter) at the downstream end of the downstream left wingwall and along the downstream right bank, type-2 stone fill (less than 36 inches diameter) along the upstream right bank and type-3 stone fill (less than 48 inches diameter) at the upstream end of the upstream 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) 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 ranged from 0.0 to 1.3 ft. The worst-case contraction scour occurred at the incipient roadway-overtopping discharge, which was less than the 100-year discharge. Abutment scour ranged from 9.4 to 12.6 ft. The worst-case abutment scour occurred at the 100-year discharge for the left abutment and at the incipient overtopping 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↗
USGS1997

Level II scour analysis for Bridge 31 (HUNTTH00220031) on Town Highway 22, crossing Brush Brook, Huntington, Vermont

This report provides the results of a detailed Level II analysis of scour potential at structure HUNTTH00220031 on Town Highway 22 crossing Brush Brook, Huntington, 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 west-central Vermont. The 5.01-mi 2 drainage area is in a predominantly rural and forested basin. In the vicinity of the study site, the surface cover consists of trees and brush. In the study area, Brush Brook has an incised, straight channel with a slope of approximately 0.06 ft/ft, an average channel top width of 44 ft and an average bank height of 4 ft. The channel bed material ranges from boulder to gravel with a median grain size (D 50 ) of 107.0 mm (0.352 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 22 crossing of Brush Brook is a 34-ft-long, one-lane bridge consisting of one 30-foot steel I-beam span (Vermont Agency of Transportation, written communication, November 30, 1995). The opening length of the structure parallel to the bridge face is 31.2 ft. The bridge is supported by vertical, concrete abutments with wingwalls. The channel is skewed approximately 15 degrees to the opening while the computed opening-skew-to-roadway is 10 degrees. The VTAOT computed opening-skewto-roadway is 2 degrees. A scour hole 1.0 ft deeper than the mean thalweg depth was observed at the downstream end of 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 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) 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 computed to be zero ft. Abutment scour ranged from 7.0 to 10.5 ft. The worst-case abutment scour occurred at the 500-year discharge for the left abutment and at the incipient-overtopping 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↗
USGS1980

Water levels in artesian and nonartesian aquifers of Florida, 1977-78

During 1977 and 1978, water levels in the Floridan aquifer throughout most of north and central peninsular Florida rose 1 to 3 feet, based on water levels measured in 380 wells selected from a network of about 5,000 observation wells for which measurements are in the files of the U.S. Geological Survey. Hydrographs of 51 wells are presented which show long-term trends of ground-water levels in selected areas of Florida. In west-central Polk County, an area of notable pumping, levels in the Floridan and other aquifers rose in response to decreased pumping of ground water for industrial use. In north Florida, levels rose from 1 to about 4 feet in Suwannee and Hamilton Counties. In northwest Florida, levels in the sand-and-gravel aquifer rose from less than 1 foot to 5 feet. Most widespread declines in ground-water levels in northwest Florida occurred in the Tallahassee area where levels declined from 1 to nearly 5 feet.

Florida↗
USGS1987

An interactive program to display user-generated or file-based maps on a personal computer monitor

PC MAP-MAKER is an ADVANCED BASIC program written to provide users of IBM XT, IBM AT, and compatible computers with a straight-forward, flexible method to display geographical data on a color or monochrome PC (personal computer) monitor. Data can be political boundaries such as State and county boundaries; natural curvilinear features such as rivers, drainage areas, and geological contacts; and points such as well locations and mineral localities. Essentially any point defined by a latitude and longitude and any line defined by a series of latitude and longitude values can be displayed using the program. PC MAP MAKER allows users to view tabular data from U.S. Geological Survey files such as WATSTORE (National Water Data Storage and Retrieval System) in a map format in a time much shorter than required by sending the data to a line plotter. The screen image can be saved to disk for recall at a later date, and hard copies can be printed with a dot matrix printer. The program is user-friendly, using menus or prompts to guide user input. It is fully documented and structured to allow the user to tailor the program to the user 's specific needs. The documentation includes a tutorial designed to introduce users to the capabilities of the program using the State of Colorado as a demonstration map area. (Author 's abstract)

Open-File Report↗
USGS2004

User's manual for the national water information system of the U.S. Geological Survey: Ground-water site-inventory system

The Ground-Water Site-Inventory (GWSI) System is a ground-water data storage and retrieval system that is part of the National Water Information System (NWIS) developed by the U.S. Geological Survey (USGS). The NWIS is a distributed water database in which data can be processed over a network of workstations and file servers at USGS offices throughout the United States. This system comprises the GWSI, the Automated Data Processing System (ADAPS), the Water-Quality System (QWDATA), and the Site-Specific Water-Use Data System (SWUDS). The GWSI System provides for entering new sites and updating existing sites within the local database. In addition, the GWSI provides for retrieving and displaying ground-water and sitefile data stored in the local database. Finally, the GWSI provides for routine maintenance of the local and national data records. This manual contains instructions for users of the GWSI and discusses the general operating procedures for the programs found within the GWSI Main Menu.

Open-File Report↗
USGS1997

Level II scour analysis for Bridge 33 (HUNTTH00220033) on Town Highway 22, crossing Brush Brook, Huntington, Vermont

This report provides the results of a detailed Level II analysis of scour potential at structure HUNTTH00220033 on Town Highway 22 crossing Brush Brook, Huntington, 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 8.65-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 on the downstream right overbank which is pasture. In the study area, Brush Brook has an incised, straight channel with a slope of approximately 0.04 ft/ft, an average channel top width of 42 ft and an average bank height of 3 ft. The channel bed material ranges from gravel to boulder with a median grain size (D 50 ) of 76.7 mm (0.252 ft). The geomorphic assessment at the time of the Level I and Level II site visit on June 26, 1996, indicated that the reach was stable. The Town Highway 22 crossing of Brush Brook is a 40-ft-long, two-lane bridge consisting of one 23.5-foot concrete slab span (Vermont Agency of Transportation, written communication, November 30, 1995). The opening length of the structure parallel to the bridge face is 36.9 ft. The bridge is supported by vertical, concrete abutments with wingwalls. The channel is skewed approximately 35 degrees to the opening while the opening-skew-to-roadway is 30 degrees. The scour protection measure at the site was type-2 stone fill (less than 36 inches diameter) along the left and right banks upstream that extended through the bridge and along 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 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 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 0.0 to 1.1 ft. The worst-case contraction scour occurred at the 500-year discharge. Abutment scour ranged from 6.5 to 14.9 ft. 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 39 (STOWTH00160039) on Town Highway 16, crossing Moss Glen Brook, Stowe, Vermont

This report provides the results of a detailed Level II analysis of scour potential at structure STOWTH00160039 on Town Highway 16 crossing Moss Glen Brook, Stowe, 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 4.75-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 and on the right bank downstream. The downstream left bank is pasture while the immediate bank has dense woody vegetation. In the study area, Moss Glen Brook has an incised, sinuous channel with a slope of approximately 0.02 ft/ft, an average channel top width of 52 ft and an average bank height of 7 ft. The channel bed material ranges from sand to cobble with a median grain size (D 50 ) of 56.5 mm (0.185 ft). The geomorphic assessment at the time of the Level I and Level II site visit on July 10, 1996, indicated that the reach was stable. The Town Highway 16 crossing of Moss Glen Brook is a 22-ft-long galvanized plate arch culvert with an opening span width of 21 ft (Vermont Agency of Transportation, written communication, October 13, 1995). The opening length of the structure parallel to the culvert face is 20.6 ft. The culvert is supported by vertical, concrete abutments with no wingwalls. The channel is skewed approximately zero degrees to the opening. The opening skew-to-roadway value from the VTAOT database is 5 degrees while zero degrees was computed from surveyed points. The only scour counter measure at the site was type-3 stone fill (less than 48 inches diameter) at the upstream and downstream ends of the left and right abutments and extending along 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 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. 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 1.2 ft. The worst-case contraction scour occurred at the 500-year discharge. Left abutment scour ranged from 12.6 to 16.2 ft. Right abutment scour ranged from 12.1 to 14.3 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↗
USGS1998

Level II scour analysis for Bridge 63 (MTH0TH00120063) on Town Highway 12, crossing Russell Brook, Mount Holly, Vermont

This report provides the results of a detailed Level II analysis of scour potential at structure MTHOTH00120063 on Town Highway 12 crossing Russell Brook, Mount Holly, 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 (FHWA, 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 3.6-mi 2 drainage area is in a predominantly rural and forested basin. In the vicinity of the study site, the surface cover is forest upstream and downstream of the bridge. In the study area, Russell Brook has an incised, sinuous channel with a slope of approximately 0.0263 ft/ft, an average channel top width of 29 ft and an average bank height of 3 ft. The channel bed material ranges from cobbles to boulders with a median grain size (D 50 ) of 97.1 mm (0.318 ft). The geomorphic assessment at the time of the Level I and Level II site visit on October 4, 1995, indicated that the reach was stable. The Town Highway 12 crossing of Russell Brook is a 29-ft-long, one-lane bridge consisting of a 26-foot steel-stringer span (Vermont Agency of Transportation, written communication, March 21, 1995). The opening length of the structure parallel to the bridge face is 23.5 ft. The bridge is supported by vertical, concrete abutments with wingwalls. The channel is skewed approximately 40 degrees to the opening while the computed opening-skew-to-roadway is 35 degrees. During the Level I assessment, it was observed that the upstream left wingwall footing was exposed 0.2 ft, in reference to the mean thalweg depth, and the upstream end of the left abutment was exposed 0.1 ft. The scour protection measure at the site was type-2 stone fill (less than 36 inches diameter) along the upstream end 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 recommended rock rip-rap sizes were computed using the general guidelines described in Hydraulic Engineering Circular 18 (Richardson and Davis, 1995) for the 100- 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 ranged from 0.0 to 0.1 ft. The worst-case contraction scour occurred at the 100-year discharge. Left abutment scour ranged from 4.4 to 5.7 ft. Right abutment scour ranged from 11.3 to 12.2 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 Davis, 1995, p. 46). 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, (MANCTH00060008) on Town Highway 6, crossing Bourn Brook, Manchester, Vermont

This report provides the results of a detailed Level II analysis of scour potential at structure MANCTH00060008 on Town Highway 6 crossing Bourn Brook, Manchester, 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 Taconic section of the New England physiographic province in southwestern Vermont. The 15.5-mi 2 drainage area is in a predominantly rural and forested basin. The bridge site is located within a suburban setting in the Town of Manchester with houses and lawns on the overbanks. In the study area, Bourn Brook has an incised, straight channel with a slope of approximately 0.01 ft/ft, an average channel top width of 61 ft and an average bank height of 7 ft. The channel bed material ranges from sand to cobbles with a median grain size (D 50 ) of 87.2 mm (0.286 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 Town Highway 6 crossing of Bourn Brook is a 44-ft-long, two-lane bridge consisting of one 41-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 40.0 ft. The bridge is supported by vertical, concrete abutments with wingwalls. The channel is skewed approximately zero degrees to the opening while the opening-skew-to-roadway is 15 degrees. A scour hole 3.5 ft deeper than the mean thalweg depth was observed along the upstream right wingwall and right abutment during the Level I assessment. The scour countermeasures at the site were stone walls in front of the upstream left wingwall and bank, along the upstream right bank extending from the end of the upstream right wingwall, and in front of the downstream right wingwall and 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) for the 100- and 500-year discharges. In addition, the incipient roadway-overtopping discharge was 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 zero ft. The left abutment scour ranged from 3.6 to 9.2 ft. The worst-case left abutment scour occurred at the 500-year discharge. The right abutment scour ranged from 9.8 to 12.6 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↗
USGS1966

Ground water in the Cimarron River basin: New Mexico, Colorado, Kansas, and Oklahoma

This report on ground water in the Cimarron River basin was prepared by the Water Resources Division of the U.S. Geological Survey at the request of the U.S. Corps of Engineers, Tulsa District, for inclusion in the Corps' overall report on the water resources of the basin. The report is an updating of the Cimarron Basin part of the report on the Arkansas, White, and Red River basins (Lohman and Burtis, 1953a) and includes more recently published data, as well as unpublished data in the files of the Geological Survey. These data are compiled by district offices of the Geological Survey in each State in cooperation with State and local agencies and with other Federal agencies. No new data were collected as a part of this investigation. The report is primarily a map presentation, and the text is intended mainly to clarify and supplement the maps and to make them more understandable and usable. The report also presents some of the ground-water problems--both present and potential--and suggests some partial solutions. As the maps and text are of necessity highly generalized, the reader is referred to the more detailed reports for more precise information.

Colorado, Kansas, New Mexico, Oklahoma↗
USGS1995

Supporting data for hydrologic studies in San Francisco Bay, California: Meteorological measurements at the Port of Redwood City during 1992-1994

Meteorological data were collected during 1992-94 at the Port of Redwood City, California, to support hydrologic studies in southern San Francisco Bay. The meteorological variables that were measured were air temperature, atmospheric pressure, quantum flux (insolation), and four parameters of wind speed and direction: scalar mean horizontal wind speed, (vector) resultant horizontal wind speed, resultant wind direction, and standard deviation of the wind direction. Hourly mean values based on measurements at five-minute intervals were logged at the site, then transferred to a portable computer monthly. Daily mean values were computed for temperature, insolation, pressure, and scalar wind speed. Hourly- mean and daily-mean values are presented in time- series plots and daily variability and seasonal and annual cycles are described. All data are provided in ASCII files on an IBM-formatted disk. Observations of temperature and wind speed at the Port of Redwood City were compared with measurements made at the San Francisco International Airport. Most daily mean values for temperature agreed within one- to two-tenths of a degree Celsius between the two locations. Daily mean wind speeds at the Port of Redwood City were typically half the values at the San Francisco International Airport. During summers, the differences resulted from stronger wind speeds at the San Francisco International Airport occurring over longer periods of each day. A comparison of hourly wind speeds at the Palo Alto Municipal Airport with those at the Port of Redwood City showed that values were similar in magnitude.

California↗
USGS1998

Preliminary report on coal resources of the Wyodak-Anderson coal zone, Powder River Basin, Wyoming and Montana

The National Coal Resource Assessment (NCRA) project by the U.S. Geological Survey is designed to assess US coal with the greatest potential for development in the next 20 to 30 years. Coal in the Wyodak-Anderson (WA) coal zone in the Powder River Basin of Wyoming and Montana is plentiful, clean, and compliant with EPA emissions standards. This coal is considered to be very desirable for development for use in electric power generation. The purpose of this NCRA study was to compile all available data relating to the Wyodak- Anderson coal, correlate the beds that make up the WA coal zone, create digital files pertaining to the study area and the WA coal, and produce a variety of reports on various aspects of the assessed coal unit. This report contains preliminary calculations of coal resources for the WA coal zone and is one of many products of the NCRA study. Coal resource calculations in this report were produced using both public and confidential data from many sources. The data was manipulated using a variety of commercially available software programs and several custom programs. A general description of the steps involved in producing the resource calculations is described in this report.

North Dakota, South Dakota, Montana, Wyoming↗
USGS1997

Level II scour analysis for Bridge 43 (CHELTH00460043) on Town Highway 46, crossing Jail Brook, Chelsea, Vermont

This report provides the results of a detailed Level II analysis of scour potential at structure CHELTH00460043 on Town Highway 46 crossing Jail Brook, Chelsea, 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 central Vermont. The 4.68-mi 2 drainage area is in a predominantly rural and forested basin. In the vicinity of the study site, the surface cover is best described as suburban with homes, lawns, and a few trees. In the study area, Jail Brook has an incised, straight channel with a slope of approximately 0.02 ft/ft, an average channel top width of 32 ft and an average bank height of 6 ft. The channel bed material ranges from coarse sand to boulder with a median grain size (D 50 ) of 43.0 mm (0.141 ft). The geomorphic assessment at the time of the Level I and Level II site visit on November 18, 1994, indicated that the reach was stable. The Town Highway 46 crossing of Jail Brook is a 27-ft-long, two-lane bridge consisting of one 23-foot concrete span (Vermont Agency of Transportation, written communication, August 25, 1994). The opening length of the structure parallel to the bridge face is 22.8 ft.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. Channel scour was not observed. However, the left abutment footing was exposed one foot. Scour countermeasures at the site consisted of type-2 stone fill (less than 36 inches diameter) on the banks and road embankments upstream and 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. Contraction scour for all modelled flows ranged from 1.1 to 1.2 ft. The worst-case contraction scour occurred at the 500-year discharge. Abutment scour ranged from 5.0 to 6.5 ft at the left abutment and 4.7 to 6.2 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”. 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 16 (CHESVT01030016) on State Route 103, crossing the Williams River, Chester, Vermont

This report provides the results of a detailed Level II analysis of scour potential at structure CHESVT01030016 on State Route 103 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 15.1-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 downstream right overbank which is forested. In the study area, the Williams River has an incised, straight channel with a slope of approximately 0.008 ft/ft, an average channel top width of 56 ft and an average bank height of 6 ft. The channel bed material ranges from gravel to cobbles with a median grain size (D 50 ) of 67.5 mm (0.222 ft). The geomorphic assessment at the time of the Level I and Level II site visit on September 16, 1996, indicated that the reach was stable. The State Route 103 crossing of the Williams River is a 162-ft-long, two-lane bridge consisting of three steel-beam spans (Vermont Agency of Transportation, written communication, March 13, 1995). The opening length of the structure parallel to the bridge face is 157.7 ft.The bridge is supported by vertical, concrete abutments and piers with no wingwalls. The channel is skewed approximately 55 degrees to the opening while the opening-skew-to-roadway is also 55 degrees. The scour protection measures at the site included type-4 stone fill (less than 60 inches diameter) along the upstream left bank. There was type-3 stone fill (less than 48 inches diameter) along the upstream right bank and both spill-through embankments and both downstream banks. There was type-1 stone fill (less than 12 inches diameter) along the upstream right and downstream left road embankments. 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 0.0. Abutment scour ranged from 6.4 to 9.0 ft. The worst-case abutment scour occurred at the 500-year discharge. Pier scour ranged from 7.9 to 10.1 ft. The worst-case pier scour occurred at the incipient-overtopping discharge for both piers. 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 28 (CAMBTH00460028) on Town Highway 46, crossing the Seymour River, Cambridge, Vermont

This report provides the results of a detailed Level II analysis of scour potential at structure CAMBTH00460028 on Town Highway 46 crossing the Seymour River, Cambridge, 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 9.94-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 dense woody vegetation. In the study area, the Seymour River has an incised, straight channel with a slope of approximately 0.02 ft/ft, an average channel top width of 81 ft and an average bank height of 5 ft. The channel bed material ranges from gravel to boulder with a median grain size (D 50 ) of 62.0 mm (0.204 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 stable. The Town Highway 46 crossing of the Seymour River is a 38-ft-long, one-lane bridge consisting of one 33-foot steel-beam span (Vermont Agency of Transportation, written communication, March 8, 1995). The opening length of the structure parallel to the bridge face is 30.6 ft.The bridge is supported by vertical, concrete abutments with wingwalls. The channel is skewed approximately 5 degrees to the opening while the measured opening-skew-to-roadway is 10 degrees. A scour hole 0.2 ft deeper than the mean thalweg depth was observed along the upstream right wingwall and right abutment during the Level I assessment. The only scour protection measure at the site was type-1 stone fill (less than 12 inches diameter) along the upstream 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) 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 ranged from 0.0 to 0.8 ft. The worst-case contraction scour occurred at the incipient roadway-overtopping discharge. Left abutment scour ranged from 4.2 to 4.9 ft. The worst-case left abutment scour occurred at the 500-year discharge. Right abutment scour ranged from 8.8 to 9.7 ft. The worst-case right 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↗