Drainage Rights

1
Drainage Rights

• Dr. Matt Helmers
• Assistant Professor and Extension Agricultural
  Engineer
• Department of Agricultural and Biosystems
  Engineering
• Iowa State University

2
Drainage Rights

• Drainage is necessary for crop production in many
  areas of Iowa
• Landowners are sensitive to practices that have
  potential to negatively impact drainage on their
  land

3
Drainage Rights and the IOWA CREP Program

• Technical advisory committee established to
  assist and advise the Iowa CREP on technical
  issues related to design and locations of
  wetlands to protect rights of individuals and
  Drainage Districts

4
Technical Issues Specifically related to Drainage
Rights

• Vertical separation between tile line invert and
  normal water level of wetland
• Maintain drainage rights of upstream landowners
• Backwater surcharging of tile lines outside of
  the CREP easement area
• Wetland outlet/inlet designs for wetlands inside
  the tile zone
• Design standards to preserve rights of future
  drainage district improvements

5
Technical Issues with Iowa CREP Wetland Design

• Vertical separation between a tile line invert
  and the normal water level of wetland or low flow
  water level of a channel
• 1 foot separation adequate for tile outlets
• Limit principal spillway design for storm stage
  event to 3.5 feet or less where auxiliary
  spillway is provided

6
(No Transcript)
7
Technical Issues with Iowa CREP Wetland Design

• Backwater surcharging tile lines outside of the
  CREP easement area
• Committee concurred that no adverse effects would
  result to existing tile on adjacent property if
  the guidelines detailed in vertical separation
  are followed.
• Easements would be offered to the adjacent
  landowner under these circumstances, but would
  not stop the project from moving forward,
  provided adjacent landowner still consents to the
  project.

8
Technical Issues with Iowa CREP Wetland Design

• Wetland outlet/inlet designs for wetlands in the
  tile zone
• Recommend gravity flow designs with language Not
  more than 100 of gravity flow when downstream
  data is known, unless other information exists
  that prescribes some process to protect drainage
  rights.
• For drawdown structures, install orifice that
  limits outflow to 75 of tile capacity (Q) along
  with an approved management plan that allows for
  drawdown not sooner than 7 days following rain
  events greater than 2.
• Consider modified inlet protectors to lesson the
  build up of debris.

9
Technical Issues with Iowa CREP Wetland Design

• Design standards to preserve rights of future
  drainage improvements within the watershed
• Shall allow for future drainage improvements to
  the most distant area, or lowest area, or the
  combination of both, that potentially may be
  drained by limiting normal wetland pool elevation
  such that a vertical difference of one foot for
  the outlet overfall, plus 0.001 grade from the
  pool to the potential new outlet, plus four feet
  for tile depth at the potential area to be
  drained.

10
Watershed Area
County Road
Constructed Wetland
Intake
Berm
Outlet Structure
PROFILE
Road
Hydraulic grade line
OUTLET STRUCTURE DESIGN CONSIDERATIONS