New Drainage Initiatives

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New Drainage Initiatives
2008 Partnering Conference

• David Moses
• Chief Drainage Engineer
• Kentucky Transportation Cabinet

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New Drainage ManualGeneral Information
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Slow Going Until We Had a Breakthrough
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Manual Layout

• Keeping Same Basic Chapter Layout

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Manual Layout

• Same layout as the Design Manual
• Chapters will be divided into subjects with
  separate page numbering
• Footers will indicate the effective date of each
  subject
• Criteria Summary at the end of each chapter

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Criteria Summary
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Final Format
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Rewrite Process

• Draft theory chapters first, then focus on
  policy and procedure chapters
• Drafts sent out to Preliminary Review Committee
• Three Chapters Currently under Preliminary Review
• Chapter 2 - Stormwater Floodplain Management
• Chapter 4 Hydrology
• Chapter 9 Dams Storage

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Preliminary Review Committee
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After Preliminary Review

• After Preliminary Review, Corrections and Changes
  Made
• Chapters Will Be Officially Released by Design
  Memo
• With Release of Design Memo the Policy Will
  Become Effective, However a Grace Period Will
  Apply
• Projects That Have Already Had Preliminary Folder
  Submitted Can Use Previous Policy

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After Official Release

• Each Chapter Will Be Released Electronically Via
  Drainage Website
• 3 Month Comment Period to Allow for Errors
• After 3 month Period Some (hopefully minor)
  Revisions May be Necessary

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Drafted Chapter Highlights
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Ch 2 - Stormwater Floodplain Management

• More coordination with DOW and local floodplain
  coordinators
• Floodway analyses only necessary when a FEMA
  mapped floodway is encroached upon
• No Rise certifications will be required in
  certain cases when FEMA mapped floodways are
  encroached upon
• Allowable Rise concept based on either local
  criteria, state criteria or cumulative rise

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Chapter 4 Hydrology

• Updated Regional Method
• Adoption of NRCS (formerly SCS) Unit Hydrograph
  Method (When Hydrograph Analysis is Required)

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Chapter 9

• Refers to Division of Water Criteria for Dams
• Detention Basin Criteria For All Basins
• Limit post construction peak discharges from the
  basin to the pre construction (existing) peak
  discharges for the 2 year, 10 year and 100 year,
  24 hour SCS Type II design storms.
• The water surface elevation in the basin
  resulting from the 100 year storm should be a
  minimum of 1 below the top of basin (point where
  water begins to overflow) when assuming all
  spillways and/or outlets are functional.

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Chapter 9

• Basins with separate emergency spillway
• Design the emergency spillway to convey the 100
  year flow, without overtopping the basin, by
  assuming the principal spillway is clogged.
• Basins without a separate emergency spillway
• Ensure that clogging of the principal spillway
  pipe is addressed by constructing an outlet
  structure that has openings that are either
  smaller that the principal spillway pipe, or are
  protected by grates.

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Policy Direction of Future Chapters
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Spread Criteria

• Based solely on spread into a driving lane

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Channel Design

• Thresholds that require no calculations
• Area?
• Flowrate?
• Slope?
• Inclusion of Turf Reinforcing Mats

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Temporary Drainage Design

• All drainage design is based on acceptable levels
  of risk
• Design of temporary structures highlights this
  concept

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Risk Assessment

• For example
• A claming horse has been running at the 10,000
  level in his last three races and has finished in
  the money in all three races. This horse is
  going off at 81
• Another horse in the race, has been running in
  70,000 allowance races and has been finishing in
  the middle of the pack. This horse is going off
  at 41
• What is the best way to double your money?

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Answer

• Fold your money in half and put it back in your
  pocket
• This will save money that can be used to buy a
  beer later

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Temporary Drainage Design / Risk Assessment

• Key Concept Examples
• A diversion that is built for a construction
  project that will last for only 3 months has a
  much smaller risk of seeing a large storm than
  one where the diversion will remain in place for
  2 years.
• Diversions in highly populated areas with houses
  in close proximity to the structure should be
  designed to higher levels than one where no
  dwellings are located.
• There is less acceptance to a temporary diversion
  flooding on a highly traveled route with no close
  detour as opposed to a route with low traffic or
  a close detour

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Temporary Drainage Design

• As with any stream crossing, temporary structures
  should be design to accommodate larger floods
  than the design flood. This accomplishes two
  primary goals
• Reduce damages from larger floods
• Avoid total washout of diversion
• This is usually accomplished by ensuring that
  anything over the design storm overtops the
  structure.

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Two Primary Considerations in Determining overall
Risk

• Frequency that a undesired event will happen
• Impact of the event

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Guidance On Surveying For Hydraulic Structures

• Preliminary Hydraulic Runs?
• Written for the Survey Crew
• Length Downstream and Upstream of a structure
• Hydraulic Section Survey (Perpendicular to Flow)
• Whole Floodplain Coverage

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Hydraulic Sections
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Structure Layout Information

• What information is important to convey to
  bridges
• Proper Skew Definitions
• Wing Layouts
• Actual Culvert Lengths

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Floodplain Coverage
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Software Policy

• Recommendations or Requirements?
• Narrow to a short list

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