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Design for Stream Crossing Resiliency ….by accounting for natural stream processes.

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Presentation on theme: "Design for Stream Crossing Resiliency ….by accounting for natural stream processes."— Presentation transcript:

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2 Design for Stream Crossing Resiliency ….by accounting for natural stream processes

3 Design for Stream Crossing Resiliency More frequent, more intense storms: Streams convey more water…

4 Design for Stream Crossing Resiliency More frequent, more intense storms: Streams convey more water… …sediment

5 Design for Stream Crossing Resiliency More frequent, more intense storms: Streams convey more water… …sediment

6 Design for Stream Crossing Resiliency More frequent, more intense storms: Streams convey more water… …sediment …and debris …and debris

7 Design for Stream Crossing Resiliency More frequent, more intense storms: Streams convey more water… …sediment …and debris …and debris

8 Design for Stream Crossing Resiliency… …streams also convey wildlife

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10 Habitat Connectivity & Flood Resiliency: A “Win-Win” Design Scenario

11 River and Stream Continuity Partnership Guidance: MA River and Stream Crossing Standards General Standards 1. Spans (bridges, open-bottom culverts) strongly preferred (but where these are impractical, well designed culverts may be appropriate) 2. If culvert, then it should be embedded 3. Span the channel: 1.2 x bankfull width 4. Natural bottom substrate within structure 5. Design with streambed characteristics 6. Openness > 0.82 feet (0.25 meters )

12 1. Apply the Stream Crossing Standards* 2. Design for Capacity and Stability 3. Provide for Resiliency *Applicable for non-tidal streams… For tidal streams: preserve or restore natural tidal exchange. Smart Stream Crossing Design:

13 1. Apply the Stream Crossing Standards Convey the “bankfull discharge” through the crossing in a sustainable, natural channel (for replacement structures: to the extent practicable) Smart Stream Crossing Design:

14 1. Apply the Stream Crossing Standards Convey the “bankfull discharge” through the crossing in a sustainable, natural channel (for replacement structures: to the extent practicable) 2. Design for Capacity and Stability Convey a range of greater than bankfull flows, while sustaining this natural channel and the structure Smart Stream Crossing Design:

15 1. Apply the Stream Crossing Standards Convey the “bankfull discharge” through the crossing in a sustainable, natural channel (for replacement structures: to the extent practicable) 2. Design for Capacity and Stability Convey a range of greater than bankfull flows, while sustaining this natural channel and the structure 3. Provide for Resiliency Withstand extreme events without losing the structure Smart Stream Crossing Design:

16 Cross Section Geometry Cross Section Geometry Streambed Streambed Vertical Alignment Vertical Alignment Smart Stream Crossing Design: 1. Apply the Stream Crossing Standards Convey the “bankfull discharge” through the crossing in a sustainable, natural channel

17 Cross Section Geometry Cross Section Geometry Streambed Streambed Vertical Alignment Vertical Alignment Smart Stream Crossing Design: 1. Apply the Stream Crossing Standards

18 A brief primer on “Bankfull Width”

19 Design to the River and Stream Crossing Standards

20 Bankfull Discharge Bankfull discharge = the water discharged when a stream just begins to overflow into the active floodplain. Bankfull stage = the elevation at bankfull discharge Bankfull width = the width at bankfull stage

21 Design to the River and Stream Crossing Standards Bankfull Stage Bankfull discharge ~ 1.5 Year Frequency Event (varies)

22 Design to the River and Stream Crossing Standards Topographic breaks in slope Depositional features Changes in vegetation Changes in bank material particle size Undercuts in bank Other erosion features on upper bank (e.g., scour around roots) Stain lines or lower extent of lichens or mosses on boulders or structures Flat depositional surface of the floodplain Bankfull Stage

23 Bankfull Width Design to the River and Stream Crossing Standards Bankfull Stage

24 Bankfull Width 1.2 x Bankfull Width Design to the River and Stream Crossing Standards

25 Bankfull Width 1.2 x Bankfull Width Span: bridge or open bottom culvert

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28 Bankfull width

29 Bridge span

30 Span: bridge or open bottom culvert Open Area Open Area (ft 2 ) Structure Length (ft) = Openness Ratio (ft) Openness Ratio (m) > 0.82 ft for General Standards* (*Optimum Standards have greater openness and minimum clearance requirements)

31 Cross Section Geometry Cross Section Geometry Streambed Streambed Vertical Alignment Vertical Alignment Smart Stream Crossing Design: 1. Apply the Stream Crossing Standards

32 Span: bridge or open bottom culvert Preserve existing stream bed (preferred); or if necessary, Provide for bed material comparable to natural channel and that results in depths and velocities at a variety of flows.

33 Culvert with Stream Simulation Streambed 1.2 x Bankfull Width

34 Requires analysis of Streambed material Streambed material Design for the Streambed

35 Requires analysis of Streambed material Streambed material Design for the Streambed

36 Requires analysis of Streambed material Streambed material Bedform (how the material is arranged in the natural channel) Bedform (how the material is arranged in the natural channel) Design for the Streambed

37 Requires analysis of Streambed material Streambed material Bedform (how the material is arranged in the natural channel) Bedform (how the material is arranged in the natural channel) Requires an understanding of stream morphology

38 Crossing design for a steep gradient boulder & cobble dominated stream…

39 …may differ from the design for a flatter- gradient stream with a sand & gravel bed.

40 Cross Section Geometry Cross Section Geometry Streambed Streambed Vertical Alignment Vertical Alignment Smart Stream Crossing Design: 1. Apply the Stream Crossing Standards

41 From Gubernick & Bates, Stream Simulation Design for AOP, Culvert Summit 2006 Analysis of the “Long Profile”

42 From Gubernick & Bates, Stream Simulation Design for AOP, Culvert Summit 2006 Analysis of the “Long Profile”

43 From Gubernick & Bates, Stream Simulation Design for AOP, Culvert Summit 2006 Analysis of the “Long Profile” New Span

44 Capacity for Design Flows Capacity for Design Flows Stability Considerations Stability Considerations Smart Stream Crossing Design: 2. Design for Capacity and Stability Convey a range of greater than bankfull flows, while sustaining this natural channel and the structure

45 Capacity for Design Flows Capacity for Design Flows Base flows addressed by bankfull channel design Base flows addressed by bankfull channel design Peak flows based on accepted engineering standards Peak flows based on accepted engineering standards Smart Stream Crossing Design: 2. Design for Capacity and Stability

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47 Engineering Design Standards Statutory Review Requirements MGL Chapter 85 MGL Chapter 85 No bridge on a public highway having a span in excess of ten feet… shall be constructed or reconstructed by any county or town except in accordance with plans and specifications therefor approved by the department. Said department shall approve or alter to meet its approval all such plans submitted to it and shall determine the maximum load which any such bridge may safely carry… No bridge on a public highway having a span in excess of ten feet… shall be constructed or reconstructed by any county or town except in accordance with plans and specifications therefor approved by the department. Said department shall approve or alter to meet its approval all such plans submitted to it and shall determine the maximum load which any such bridge may safely carry… Requires review by MassDOT District/Bridge Requires review by MassDOT District/Bridge Applies to any span >10 ft (including multiple barrels) Applies to any span >10 ft (including multiple barrels)

48 Item 49 – USDOT Recording and Coding Guide for the Structure Inventory and Appraisal of the Nation’s Bridges Item 49 – USDOT Recording and Coding Guide for the Structure Inventory and Appraisal of the Nation’s Bridges Engineering Design Standards Statutory Review Requirements

49 MGL Chapter 85 MGL Chapter 85 Design to MassDOT/ASHTO bridge standards Design to MassDOT/ASHTO bridge standards 2009 MassDOT LRFD Bridge Manual 2009 MassDOT LRFD Bridge Manual AASHTO LRFD Bridge Design Specifications AASHTO LRFD Bridge Design Specifications Submittal Requirements Submittal Requirements Hydraulic report Hydraulic report Geotechnical report Geotechnical report Structural design requirements Structural design requirements Scour analysis/scour protection at spans Scour analysis/scour protection at spans Engineering Design Standards Statutory Review Requirements

50 Smart Stream Crossing Design: 2. Design for Capacity and Stability Design Flows – what about climate change? Precipitation Data Precipitation Data TP-40 is out of date TP-40 is out of date New data options… New data options… Stream Gage Data Stream Gage Data USGS Regression Equations for Massachusetts are out of date USGS Regression Equations for Massachusetts are out of date New data options… New data options… Even with updated data, forecasting using historic data may be problematic Even with updated data, forecasting using historic data may be problematic Provide for resiliency… Provide for resiliency…

51 NRRC and NRCS Precipitation Data: current option… Greatly expanded and recent data base Greatly expanded and recent data base Authorized by NRCS for TR-55 and TR-20 until NWS Atlas 14 is updated Authorized by NRCS for TR-55 and TR-20 until NWS Atlas 14 is updated Not formally adopted by MassDEP Not formally adopted by MassDEP

52 County Rainfall Depth (in) Percent Change TP-40NRCC Barnstable % Berkshire North2.8 0% Berkshire south2.9 0% Bristol % Dukes % Essex % Franklin % Hampden % Hampshire % Middlesex North3.0 0% Middlesex Central3.1 1% Middlesex South % Nantucket % Norfolk % Plymouth3.4 -1% Suffolk % Worcester North % Worcester Central % Worcester South % 2 year County Rainfall Depth (in) Percent Change TP-40NRCC Barnstable % Berkshire North % Berkshire south % Bristol % Dukes % Essex % Franklin % Hampden % Hampshire % Middlesex North % Middlesex Central % Middlesex South % Nantucket % Norfolk % Plymouth % Suffolk % Worcester North % Worcester Central % Worcester South % 100 year

53 NOAA Atlas 14 Precipitation Frequency Estimates Volume 10: Northeastern States Projected web-publication: September 2015 Precipitation Data: on the horizon…

54 Regional Regression Equations for Peak Discharges MassDOT/USGS update is underway. Scheduled for completion late 2015 (Published 1983)

55 Stability Considerations Stability Considerations Stream bed sustainability Stream bed sustainability Structure integrity Structure integrity Smart Stream Crossing Design: 2. Design for Capacity and Stability

56 Streams are dynamic Bridges and culverts are static (or intended to be!) Smart Stream Crossing Design: 2. Design for Capacity and Stability

57 Streams are dynamic… …crossing structures are static …crossing structures are static

58 Streams are dynamic… Culverts are rigid horizontally and vertically Stream bed horizontal and vertical adjustment limited to material in the culvert Culvert bottom acts as a “grade control” structure

59 Streams are dynamic… ….culverts are rigid However, “stream simulation” culvert design can prevent this condition

60 Bridges and open bottom culverts are rigid horizontally (unless undermined!) Stream bed vertical adjustment is not limited by the bottom of the structure Future channel? Streams are dynamic…

61 …bridges are rigid horizontally …bridges are rigid horizontally …however, this can (and must) be addressed by design.

62 Requires analysis of Stability of the crossing structure: protect (sustain) the bridge! Stability of the crossing structure: protect (sustain) the bridge! Dynamic stability of the streambed material: sustain the streambed! Dynamic stability of the streambed material: sustain the streambed! Design for stability

63 “Critical Conditions” design Structure stability under critical conditions: Structure stability under critical conditions: MassDOT LRFD Bridge Design Manual (check for latest revision): MassDOT LRFD Bridge Design Manual (check for latest revision): Evaluate bridge foundation scour using flow parameters of the local flood event that generates the maximum depth of bridge foundation scour- considering flood return frequencies (depending on type of road) up to 500 years. Apply countermeasures if warranted. Apply countermeasures if warranted.

64 Supplemental Guidance to LRFD Bridge Manualfor streambed design for crossings

65 Design must evaluate stability within the crossing structure… Need to address both: Base flow (habitat continuity) Extreme flow events

66 In some cases, design may need to provide for stability within the crossing structure… Stream Simulation with Stable Sub-bed Design to address foundation scour and streambed stability Design to simulate streambed material and bedform

67 RIPRAP GRADE CONTROL STRUCTURE Adapted from: US Army Engineer Research and Development Center (1999), Channel Rehabilitation: Processes, Design, and Implementation In some cases, design may need to consider stabilizing the channel… Bridge

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69 What about replacements?

70 Constraints affecting replacement to provide wildlife passage: Flood management concerns Flood management concerns Conveyance capacity Conveyance capacity Impacts on existing flood profiles Impacts on existing flood profiles Potential wetland alteration Potential wetland alteration Road impounded wetlands Road impounded wetlands Potential “head cut” considerations Potential “head cut” considerations Vertical alignment limitations Vertical alignment limitations

71 Constraints affecting replacement to provide wildlife passage: Historic structures Historic structures Existing utilities Existing utilities Construction-phase logistics Construction-phase logistics Maintaining road traffic Maintaining road traffic Maintaining stream flow (water handling) Maintaining stream flow (water handling) Site access and weight/size limits on equipment and materials Site access and weight/size limits on equipment and materials Historic structures

72 Constraints affecting replacement to provide wildlife passage: Costs and funding priorities Costs and funding priorities Mitchell Brook – before and during construction

73 Flood Profile Impacts Existing elevation of 100-year design flood Flow

74 Flood Profile Impacts Altered elevation of 100-year design flood Caution: Potential downstream flooding impacts

75 Federal Executive Order Federal Executive Order Restricts federally funded actions that would result in raising the 100 year flood elevation Restricts federally funded actions that would result in raising the 100 year flood elevation Flood Profile Impacts

76 Addressing Flood Profile Impacts: Determine if potential for alteration exists Determine if potential for alteration exists Determine whether the impact can be addressed Determine whether the impact can be addressed Alternative design approaches? Alternative design approaches? Downstream actions? Downstream actions? Determine if CLOMR (or other action) is required Determine if CLOMR (or other action) is required Document and file application Document and file application If no to above, explore other ways to mitigate for habitat disconnection: If no to above, explore other ways to mitigate for habitat disconnection: May require a lesser restoration of habitat connection May require a lesser restoration of habitat connection

77 Road-Impounded Wetlands

78 Flow Altered hydrology results in establishment of wetlands Flow constriction results in sediment deposition upstream of culvert

79 Road-Impounded Wetlands Flow More effective conveyance, lowering invert can lower upstream water surface, erode accumulated sediment, and alter wetland hydrology

80 Addressing Road-Impounded Wetlands: Determine if potential for alteration exists Determine if potential for alteration exists Determine whether the “gain” offsets the “loss” Determine whether the “gain” offsets the “loss” If yes to above, can it be permitted? If yes to above, can it be permitted? Consultation with resource agencies Consultation with resource agencies If no to above, explore other ways to mitigate for habitat disconnection: If no to above, explore other ways to mitigate for habitat disconnection: In-stream mitigation may be warranted: In-stream mitigation may be warranted: Application of stream restoration techniques to offset or correct impacts Application of stream restoration techniques to offset or correct impacts

81 Road-Impounded Wetlands Flow Install counter measure (e.g. rock weir) to prevent upstream headcutting and maintain wetland hydrology

82 Required opening height Required span Vertical alignment and bridge geometry constraints Existing vertical alignment Bridge Chord Bridge Deck New required vertical alignment

83 Existing Utilities

84 Urban channel alteration & degradation

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86 Constraints, constraints… …Some crossings need to be fixed!

87 Adapted from Gubernick, Culvert Summit 2006

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89 Some other alternatives

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91 Analysis for peak flows similar to new crossings More analysis required for “passage” flows: May need to base on less than bankfull discharge: Species/life-stage specific (consult with MassDFG), or 10% exceedance quantile, or 25% of Q 2-yr Need to evaluate culvert bed material stability relative to nearby channel stability Need to assess need for a low flow channel 90% exceedance quantile, or 7Q2 Smart Stream Crossing Design: 2. Design for Capacity and Stability Replacement Crossings

92 References for designs less than 1.2 x bankfull width ConceptsDesign analysis

93 Design methodology for providing stream bed continuity at road crossings Examples: “No-Slope” design* “No-Slope” design* “Stream Simulation” design* “Stream Simulation” design* “Roughened Channel” design* “Roughened Channel” design* Bridge replacement with retained abutments** Bridge replacement with retained abutments** *Based on work by: Kozmo (Ken) Bates (formerly with Washington DFW) and USDA Forest Service **Based on MassDOT practices

94 “No Slope” design option Applicable only to culverts, not bridges or bottomless structures Applicable only to culverts, not bridges or bottomless structures Suitable for new structures or replacements Suitable for new structures or replacements Generally limited to locations with natural gradients less than 3% Generally limited to locations with natural gradients less than 3% Most likely applicable to streams with fine-grained, mobile bed material Most likely applicable to streams with fine-grained, mobile bed material

95 4. Upstream countersink 40% of rise, maximum 3. Downstream countersink 20% of rise, minimum, or greater depth if required by MA Standards “No Slope” design option 1. Culvert installed with flat invert gradient 2. Culvert width = 1.2 x bankfull width 5. Bed material = native material, either installed or “recruited” Note: Given countersink requirements (#3,#4), maximum length of culvert will be limited by slope of stream (L < 0.2*D/s) flow

96 Stream Simulation Design Applicable to new and replacement culverts Applicable to new and replacement culverts Applicable to replacements of pipe culverts with bottomless culverts or bridge spans Applicable to replacements of pipe culverts with bottomless culverts or bridge spans Applicable to new clear-span structures where stream alignment would be altered Applicable to new clear-span structures where stream alignment would be altered Suited to moderate to high channel gradient, and locations with narrow stream valleys Suited to moderate to high channel gradient, and locations with narrow stream valleys Greater than 6% gradient may have limitations Greater than 6% gradient may have limitations Structure cross section size must be sufficient to permit access for stream bed construction Structure cross section size must be sufficient to permit access for stream bed construction

97 Stream Simulation Design Culvert installed with sloped invert Bed consists of various materials and bed forms designed based on geomorphologic analysis of local stream bed or suitable “reference” stream

98 Stream Simulation Design Alluvial (e.g., cobble/gravel) Non-alluvial (e.g. step-pool)

99 Roughened Channel Design Applicable to new and replacement culverts, where not feasible to provide width > 1.2 bankfull width Applicable to new and replacement culverts, where not feasible to provide width > 1.2 bankfull width Suited to moderate to high channel gradient, and locations with narrow stream valleys Suited to moderate to high channel gradient, and locations with narrow stream valleys Structure cross section size must be sufficient to permit access for stream bed construction Structure cross section size must be sufficient to permit access for stream bed construction May require scour protection (e.g., armoring) of channel at the culvert outlet May require scour protection (e.g., armoring) of channel at the culvert outlet Not recommended for flat-gradient streams with fine-grained mobile bed material (consider “no- slope” design instead. Not recommended for flat-gradient streams with fine-grained mobile bed material (consider “no- slope” design instead.

100 Roughened Channel Design Bed consists of material designed for stability under anticipated design flows – typically requires size of material to be comparable to the larger material found in natural channel Scour protection at outlet Shaped channel

101 Before

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105 Winter 2013

106 Bridge Replacement with Retained Abutments

107 Problematic Design Issues Climate Change Pressure Flow Flood Relief Embankment “piping” Floatation Debris Smart Stream Crossing Design: 3. Provide for Resiliency Withstand extreme events without losing the structure

108 Source: FHwA HEC-5

109 d τ = γ*d*s Bankfull condition

110 Source: FHwA HEC-5 τ = γ*d*s d Critical flood condition

111 Potential Countermeasures: Options: control depth, energy grade, or size/gradation of channel bed material: Wider structure? Valley span? Wider structure? Valley span? Flood plain relief culverts? Flood plain relief culverts? Design section of road as spillway? Design section of road as spillway? Use larger bed material size in structure? Use larger bed material size in structure? Use larger material as a sub-bed to the stream simulation bed material? Use larger material as a sub-bed to the stream simulation bed material?

112 Source: Forest Service Stream Simulation Working Group (2008), Stream Simulation Flood relief culverts, spillway

113 Source: Forest Service Stream Simulation Working Group (2008), Stream Simulation Flood relief culverts, spillway

114 Example of reinforced spillway Source:

115 Adapted from: FHwA HEC-5 Pressure Flow Issues: Seepage (piping) through embankment Free draining material for road construction is not necessarily designed for conditions when roadway acts as a dam

116 Adapted from: FHwA HEC-5 Buoyant force Pressure Flow Issues: Floatation of flexible pipe Particularly of concern with corrugated metal or other flexible pipe

117 Debris Issues

118 During Hurricane Irene

119 After Hurricane Irene

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121 Design References and Guidance

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124 _Passage_ pdf

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126 Questions?

127 Bridge Replacement with Retained Abutments

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131 After Hurricane Irene September 2011 Culvert Replacement – site with constrained access Source:

132 During Construction Source:

133 November 2012 Source:

134 Questions?


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