New Conservation Practices: Cascading Waterways, Upland Wetlands, 2-stage Ditch, Etc. - Justin McBride, Ohio Department of Agriculture, from the 2020 Conservation Tillage and Technology Conference, held March 3-4, 2020, Ada, OH, USA.

1. New Conservation Practices
Justin McBride, P.E.
Ohio Department of Agriculture
Division of Soil and Water Conservation
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2. Presentation Preview
• Basic concept of “P” movement in the
hydrologic landscape
• Two-Stage Ditches
• Upland Wetlands (for water quality)
• Cascading Waterways
• Creative process used to develop new
practices (if there’s time)
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3. Where does the “P” go?
• Phosphorus moves with water in 2 forms:
– Particulate (PP)
– Dissolved (DP)
• As water enters any conservation practice area, it
brings P with it in both forms of varying degree.
• The same is true when the water exits the conservation
practice area.
• The difference between the amount P that enters and
the amount that exits depends on the type of practice.
• Remember:
– What goes in, must come out… or must be permanently
stored.
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4. Where does the “P” go?
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Conservation
Practice
Permanent
Storage
Total P
Outflow
TotalP
W
hen
storage
isfull
Total P = PP + DP
Inflow = Outflow + Storage
Total P
Inflow

5. Compare to “N” Cycle
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Conservation
Practice
Permanent
Storage
Total N
Inflow
Total N
Outflow
TotalN
W
hen
storage
isfull
Inflow = Outflow + Storage + Leaching + N2 Gas Conversion
N
2 Gas
Denitrification
N2 Gas
Denitrification
Note: N may leach from soil in
significant amounts depending
on the conservation practice.

6. “P” and “N” Removal Mechanisms
(after they leave the field)
Phosphorus
• Adsorption (attachment) - Dissolved “P” storage
– Unreliable in natural systems
– Expensive in man-made systems
• Sedimentation – Particulate “P” storage
– Requires maintenance
• Bio-Accretion (Peat Buildup) – Long-term “Total P” storage
– Rarely designed correctly
Nitrogen
• Denitrification – “Total N” removal
– Maximize anaerobic conditions (no oxygen)
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7. New Practice #1
Two-Stage Ditch
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8. Two Stage Ditch
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9. PRE-CONSTRUCTION 2 YEARS POST-CONSTRUCTION
4 YEARS POST-CONSTRUCTION 7 YEARS POST-CONSTRUCTION
• Two stage ditches have a wider top width than a
standard “Trapezoidal Ditch”.
• Allows for a more stabile channel.
– Less ditch maintenance (dip-outs).
• May increase drainage capacity.
• Reduces N losses.
• More expensive (upfront) than a standard
trapezoidal ditch.
• Less regular maintenance cost may outweigh
increase in up front costs.
Two Stage Ditch

10. What about “P”? (2-Stage Ditch)
In all stream systems, “P” enters and exits the system in both
forms (PP + DP).
• Adsorption
– DP may adsorb to material in the benches, but, may also desorb.
• Sedimentation
– Sedimentation rates usually equal erosion rates in 2-stage
ditches.
• In most NW Ohio trapezoidal ditches, sedimentation rates exceed
erosion rates.
• However, some ditches in NW Ohio have unstable sections and may
benefit from a 2-stage ditch design.
• Bio-Accretion
– Not designed for maximum bio-accretion rates.
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11. Where should 2-Stage Ditches go?
Ditches with some or all of these characteristics
could be considered for 2-stage ditch projects:
• 1 to 3 square mile drainage area
• Failing bank slopes
• Excessive scouring
• Relatively shallow ditches
• No existing tree line along banks.
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12. New Practice #2
Upland Wetlands
(for water quality)
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• “Entrapment” mechanism
• Reduces sediment and nitrogen.
• Wildlife benefits.
• Takes a significant amount of land out of
production.
• Can be expensive to construct and maintain.
– Dikes
Upland Wetlands (for water quality)

14. What about “P”? (Upland Wetlands)
In all wetlands, “P” enters and exits the system in both
forms (PP + DP).
• Adsorption
– DP may adsorb to material in the wetlands, but, may also
desorb.
• Sedimentation
– Wetlands can be design to function similar to sediment
catchment basins.
– However, the sediment storage will eventually fill up.
• Bio-Accretion
– Can be designed to maximize bio-accretion rate (but,
usually isn’t).
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15. What about the vegetation?
• Yes, plants take up a significant amount of “P”
while they are growing.
• However, when they stop growing this “P”
removal mechanism also stops.
• Then, when the vegetation dies in the winter,
most, if not all of the “P” is released back into
the water column during decomposition.
• The only way to count on vegetation for long-
term removal of “P” is by harvesting the
vegetation every year.
– Not a realistic scenario.
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16. How to Maximize Bio-Accretion Rates
Bio-Accretion Rates can be maximized by using specific
values of the following design parameters:
• Watershed to Pool Patio (4:1)
• “P” Loading Rate (4 to 9 Lb/Ac)
• Hydraulic Loading Rate (1 inch per day)
• Hydraulic Retention Time (up to 7 days)
• Hydraulic Flow Length (Longer is better)
• Water Depth Management (always ponded)
• Plant Root-Shoot Ratio (faster is better)
• Detrital Tissue Turnover Rate (faster is better)
• Plant Species
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17. How?
1. Dikes with water level control mechanisms.
– Very common
OR
2. Shallow excavations with water level control
mechanisms.
– Rare
The main idea: We need to control the water
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23. New Practice #3
Cascading Waterway
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Grassed Waterways
• Allows surface water to channelize without
causing soil erosion.
• One of the best practices to reduce soil
eroding from gullies or washouts.
• Does not adequately remove input nutrients.

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Design Guidance Document Research Report on Maryland Site

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29. What about “P”? (Cascading Waterway)
• Adsorption
– DP may adsorb to material in the cells, but, may also
desorb.
• Sedimentation
– This is where the long term “P” storage is likely to
occur.
– However, the sediment storage will eventually fill up.
• Bio-Accretion
– Not designed for Bio-Accretion and is not feasible to
do so.
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30. Water Quality Results
Reductions Measured:
• Total Runoff = 56%
• Suspended Solids = 65%
• Total N = 64%
• Total P = 59% (63% Dissolved P)
Nutrient reduction is mostly attributed to runoff volume
reduction.
• To a smaller degree:
– Sedimentation
– Nutrient uptake
– Denitrification
– Adsorption
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31. Where does the water go?
• Evapotranspiration
– Occurs during warmer months
• Infiltration
– Highly dependent on soil drainage class
• Study sites were moderately well drained to well
drained soils.
• Most NW Ohio soils are somewhat poorly to very
poorly drained.
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32. Concerns?
• Do they work as advertised?
• NW Ohio is very different than Maryland.
• Cost
• Normal waterway costs
PLUS
• $60 to $120 per acre of watershed
• Extra Soil Disposal
• Normal waterway amount
PLUS
• 27 cubic yards per acre of watershed
• Long-term Maintenance
• Lifespan expected = 7 to 15 years
• Depends on watershed soil erosion rates
• Who is driving the tractor?
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Allen County

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Putnam County

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Seneca County

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47. Take Home Points!
• Once P get’s into concentrated surface water
flow, it’s very difficult to remove!
• Therefore, effort should be made to prevent
“P” from entering surface water flows.
• Prevention Measures
– 4R Strategies
• Containment Measures
– Drainage Water Management
– Cover Crops
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48. Questions
Justin McBride, P.E.
ODA Engineer
952 Lima Ave., Box D
Findlay, OH 45840
Office: (419) 429-8328
Cell: (614) 813-0459
justin.mcbride@agri.ohio.gov
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