Proposed Novato Creek Bank Stabilization Guidelines

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Proposed Novato Creek Bank Stabilization
Guidelines

• Questa Engineering Corp.

2
Urban Bank Stabilization Problems

• Privately owned creekbed
• Typically incising bed creating retreat of bank
  tops
• Adjacent structures need to be protected
• Large mature canopy trees
• Long-term Geomorphic evolutionary tendencies

3
Guideline Development Steps

• Assess Existing Conditions
• Conduct Hydraulic Analysis
• Determine Long Term Trends
• Define basic Creek Management Approaches
• Describe suitable bank stabilization treatments
• Provide permitting guidance for design and
  permitting of bank stabilization structures

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Existing Geomorphic Conditions

• Long Profile Analysis
• The channel has down cut about as far it can go.
  Natural bedrock controls prohibit extensive
  vertical degradation
• Bankfull Channel Dimensions
• Reach 1 - 33 top width Max depth 3 feet
• Reach 2 34 top width Max depth 3 feet
• Lack of Large Woody Debris
• Bedload D50 17 mm surface 4.8 mm subsurface
• Lateral erosion will be greatest erosion pressure
  in the reach

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Existing Erosion Canopy
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Existing Hydraulic Conditions

• Bankfull flows are at threshold of erosive
  velocities (Max. 5 to 7 fps)
• 10-year flows are above erosive velocity (Max.
  9.7 to 12.1 fps)
• Bank erosion episodic and is likely to occur at
  flows greater than bankfull, at 5 to 10 year
  intervals
• Expect projects to be developed on a 5 to 10 year
  cycle

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Existing Conditions Summary

• Channel is near stable vertically
• Lateral erosion may occur over the long-term
• The channel should managed to maintain at a
  minimum the average top-width and bottom width

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Creek Management Approaches

• Fill Approach
• Cut Approach
• Vertical Approach

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Design Approach Factors

• Adjacent structure setback - 20 distance
• Presence of Trees larger than 12 DBH within 5
  of Top-of-bank
• Average Channel Top-width
• Average Channel Mid-width
• Presence of Trees larger than 48 DBH

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Bank Stabilization Design Approach Flow Chart
DRAFT
Existing Adjacent Structure or Utility
No
Yes
Riparian Trees lt 12DBH
Trees gt 12 DBH
Building Setbackgt 20
Building Setbacklt 20
Single
Top Width lt 65
Multiple
Trees lt 12 DBH
Cut Solution
Trees gt 12 DBH
lt48 DBH
gt48 DBH
Top Width gt 65
Mid Width gt 55
Mid Width lt55
Top Width gt 65
Cut Solution/ Preserve Tree
Cut Solution/ Lose Tree
Cut Solution
Cut Solution
Fill Solution
Within 10 of TOB
Vertical Solution or Cut Solution Max feasible
Not Within 10 of TOB
Multiple
Single
Cut Solution Max. Feasible
Mid Width gt 55
Mid Widthlt55
Fill Solution
Cut Solution
Trees Not Within 10 of TOB
Trees Within 10 of TOB
Mid Width gt 55
Mid Width lt55
Mid Width lt55
Mid Widthlt55
Mid Width gt 55
Mid Width gt 55
Cut Solution Max. Feasible
Fill Solution
Cut Solution
Fill Solution
Vertical Solution
gt48 DBH
lt48 DBH
Fill Solution
Cut Solution
Mid Width lt55
Mid Width gt 55
Mid Width lt55
Mid Width gt 55
Cut Solution/ Preserve Tree
Cut Solution/ Lose Tree
Vertical Solution
Fill Solution
Fill Solution
Cut Solution

• Top Width is defined as the distance from top of
  bank to top of bank .
• MidWidth is defined as the width at half the
  distance to top of bank from the channel thalweg
• TOB Top of Bank DBH diameter as base height
  (4 above ground)
• Riparian tree is defined as any tree within 10
  feet of existing top of bank
• Adjacent structure/utility is a structure that is
  permitted through existing city ordinances or is
  more than 10 years old
• Fences are not considered structures

FIGURE
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Approach Check

• Station 83925
• Priority R1-2
• Structures Shed within 20 of TOB
• Trees one stump within 5 of TOB
• Top Width 55
• Mid Width 46
• Solution ? Vertical or Cut max feasible

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Priority R1-3 (Station 84350)

• Structures House within 20 of TOB
• Trees multiple trees less than 12 DBH within
  5 of TOB
• Top Width 45
• Mid Width 30
• Solution ?

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Bank Stabilization Design Approach Flow Chart
DRAFT
Existing Adjacent Structure or Utility
No
Yes
Riparian Trees lt 12DBH
Trees gt 12 DBH
Building Setbackgt 20
Building Setbacklt 20
Single
Top Width lt 65
Multiple
Trees lt 12 DBH
Cut Solution
Trees gt 12 DBH
lt48 DBH
gt48 DBH
Top Width gt 65
Mid Width gt 55
Mid Width lt55
Top Width gt 65
Cut Solution/ Preserve Tree
Cut Solution/ Lose Tree
Cut Solution
Cut Solution
Fill Solution
Within 10 of TOB
Vertical Solution or Cut Solution Max feasible
Not Within 10 of TOB
Multiple
Single
Cut Solution Max. Feasible
Mid Width gt 55
Mid Widthlt55
Fill Solution
Cut Solution
Trees Not Within 10 of TOB
Trees Within 10 of TOB
Mid Width gt 55
Mid Width lt55
Mid Width lt55
Mid Widthlt55
Mid Width gt 55
Mid Width gt 55
Cut Solution Max. Feasible
Fill Solution
Cut Solution
Fill Solution
Vertical Solution
gt48 DBH
lt48 DBH
Fill Solution
Cut Solution
Mid Width lt55
Mid Width gt 55
Mid Width lt55
Mid Width gt 55
Cut Solution/ Preserve Tree
Cut Solution/ Lose Tree
Vertical Solution
Fill Solution
Fill Solution
Cut Solution

• Top Width is defined as the distance from top of
  bank to top of bank .
• MidWidth is defined as the width at half the
  distance to top of bank from the channel thalweg
• TOB Top of Bank DBH diameter as base height
  (4 above ground)
• Riparian tree is defined as any tree within 10
  feet of existing top of bank
• Adjacent structure/utility is a structure that is
  permitted through existing city ordinances or is
  more than 10 years old
• Fences are not considered structures

FIGURE
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Priority R2-4 (Station 91900)

• Structures within 20 of TOB
• Trees two trees greater than 12 DBH within 5
  of TOB none greater than 48 DBH
• Top Width 90
• Mid Width 40
• Solution ? Vertical solution

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Bank Stabilization Design Approach Flow Chart
DRAFT
Existing Adjacent Structure or Utility
No
Yes
Riparian Trees lt 12DBH
Trees gt 12 DBH
Building Setbackgt 20
Building Setbacklt 20
Single
Top Width lt 65
Multiple
Trees lt 12 DBH
Cut Solution
Trees gt 12 DBH
lt48 DBH
gt48 DBH
Top Width gt 65
Mid Width gt 55
Mid Width lt55
Top Width gt 65
Cut Solution/ Preserve Tree
Cut Solution/ Lose Tree
Cut Solution
Cut Solution
Fill Solution
Within 10 of TOB
Vertical Solution or Cut Solution Max feasible
Not Within 10 of TOB
Multiple
Single
Cut Solution Max. Feasible
Mid Width gt 55
Mid Widthlt55
Fill Solution
Cut Solution
Trees Not Within 10 of TOB
Trees Within 10 of TOB
Mid Width gt 55
Mid Width lt55
Mid Width lt55
Mid Widthlt55
Mid Width gt 55
Mid Width gt 55
Cut Solution Max. Feasible
Fill Solution
Cut Solution
Fill Solution
Vertical Solution
gt48 DBH
lt48 DBH
Fill Solution
Cut Solution
Mid Width lt55
Mid Width gt 55
Mid Width lt55
Mid Width gt 55
Cut Solution/ Preserve Tree
Cut Solution/ Lose Tree
Vertical Solution
Fill Solution
Fill Solution
Cut Solution

• Top Width is defined as the distance from top of
  bank to top of bank .
• MidWidth is defined as the width at half the
  distance to top of bank from the channel thalweg
• TOB Top of Bank DBH diameter as base height
  (4 above ground)
• Riparian tree is defined as any tree within 10
  feet of existing top of bank
• Adjacent structure/utility is a structure that is
  permitted through existing city ordinances or is
  more than 10 years old
• Fences are not considered structures

FIGURE
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Priority R2-6 (Station 92200)

• Structures none within 20 of TOB
• Trees roughly 6 trees greater than 12 DBH
  within 5 of TOB none greater than 48 DBH
• Top Width 90
• Mid Width 56
• Solution ?

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Bank Stabilization Design Approach Flow Chart
DRAFT
Existing Adjacent Structure or Utility
No
Yes
Riparian Trees lt 12DBH
Trees gt 12 DBH
Building Setbackgt 20
Building Setbacklt 20
Single
Top Width lt 65
Multiple
Trees lt 12 DBH
Cut Solution
Trees gt 12 DBH
lt48 DBH
gt48 DBH
Top Width gt 65
Mid Width gt 55
Mid Width lt55
Top Width gt 65
Cut Solution/ Preserve Tree
Cut Solution/ Lose Tree
Cut Solution
Cut Solution
Fill Solution
Within 10 of TOB
Vertical Solution or Cut Solution Max feasible
Not Within 10 of TOB
Multiple
Single
Cut Solution Max. Feasible
Mid Width gt 55
Mid Widthlt55
Fill Solution
Cut Solution
Trees Not Within 10 of TOB
Trees Within 10 of TOB
Mid Width gt 55
Mid Width lt55
Mid Width lt55
Mid Widthlt55
Mid Width gt 55
Mid Width gt 55
Cut Solution Max. Feasible
Fill Solution
Cut Solution
Fill Solution
Vertical Solution
gt48 DBH
lt48 DBH
Fill Solution
Cut Solution
Mid Width lt55
Mid Width gt 55
Mid Width lt55
Mid Width gt 55
Cut Solution/ Preserve Tree
Cut Solution/ Lose Tree
Vertical Solution
Fill Solution
Fill Solution
Cut Solution

• Top Width is defined as the distance from top of
  bank to top of bank .
• MidWidth is defined as the width at half the
  distance to top of bank from the channel thalweg
• TOB Top of Bank DBH diameter as base height
  (4 above ground)
• Riparian tree is defined as any tree within 10
  feet of existing top of bank
• Adjacent structure/utility is a structure that is
  permitted through existing city ordinances or is
  more than 10 years old
• Fences are not considered structures

FIGURE
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Stabilization Treatments
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Design Guidance Appendix

• Design Goals and Design Requirements
• Project Permitting Approval Process
• Design Steps
• Existing County and City Ordinances