Push-Up Greens Drainage: Visualized You know you have poor drainage when you see: Dr. Ed McCoy Ohio State University Water on the surface hours after a.

Push-Up Greens Drainage: Visualized

You know you have poor drainage when you see:

Dr. Ed McCoyOhio State University

Water on the surface hours after a rain.

You know you have poor drainage when you see:

A thin turf stand.

Wet, soft greens.

You know you have poor drainage when you see:

Moss.

Black layer.

From a playability perspective, improved drainage serves to increase the firmness of the surface because soils typically gain strength when drier.

There are 2 goals for improved drainage on greens.

From an agronomic perspective, improved drainage is the opening of air-filled pores in the surface layer to improve soil aeration.

So how does one deal with a slowly draining push-up green …

having a shallow, sandy topdressing layer underlain by a fine textured soil?

Consider a 12-ft section through a push-up green …

4-inch topdressing layer

native soilhaving a soil profile as shown.

12-ft

Consider 2 scenarios: 1) a 2-inch pipe at a 16-inch depth and 2) the same but with a sandy backfill.

Then, lets rain on these greens at 0.2 inches per hour for 5 hours delivering a 1-inch rainfall.

These animations show water flow in the greens over 42 hours.

My analysis also allows calculation of an Aeration Stress Index (greater values imply greater stress) to compare turfgrass response to soil moisture conditions.

Time (days)

Ae

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on

Str

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s I

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ex

(%

)

0 1 2 30

20

40

60

80

100

12-ft Spacing12-ft Spacing, Sandy Backfill

These figures show the path of water flow to the drain for the 2 scenarios.

For the backfilled trench scenario, water flow by-passes the slowly permeable clay loam soil.

And comparing 16- vs. 24-inch pipe depth with a sandy backfill shows little difference.

Time (days)

Ae

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Str

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ex

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0 1 2 30

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12-ft Spacing, Sandy Backfill12-ft Spacing, Deep Sandy Backfill

Is pipe placement at 12-ft centers fast enough?

Even with a sandy backfill?

Well, then lets consider two closer spacing scenarios.

Shown on top we have 6-ft drainage spacing and on bottom we have 3-ft drainage spacing.

These animations show water flow in the greens over 42 hours.

The Aeration Stress Index shows faster drainage at 3-ft spacing than at 6-ft spacing.

Time (days)

Ae

rati

on

Str

es

s In

de

x (

%)

0 1 2 30

20

40

60

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6-ft Spacing, Sandy Backfill3-ft Spacing, Sand Curtain

Flow path analysis shows that at 3-ft spacing only a narrow sand curtain is required to by-pass the clay loam soil.

Considering all 4 scenarios, one sees the benefit of closer spacing for more rapid drainage.

Time (days)

Aer

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tres

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(%

)

0 1 2 30

20

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12-ft Spacing12-ft Spacing, Sandy Backfill6-ft Spacing, Sandy Backfill3-ft Spacing, Sand Curtain

6-ft spacing across the green is the conventional method of push-up greens drainage and require trenching and laying of pipe.

In this particular case, the trenches are 4-inches wide to 16-inches depth. A 2-inch pipe is placed at the bottom and a sandy backfill is added to near the surface. The stripped sod is then replaced.

But how does one reasonably install drainage elements at 3-ft spacing?

This is accomplished with the Passive Capillary Drainage (PCD) element (my invention). A 1-inch diameter bundle of wettable fibers with a 3/8th inch hollow core.

sand curtain

Installed at a 10-inch depth and with a 3/8th inch sand curtain backfill.

The Passive Capillary Drainage System

Installed only in areas within a green where needed.

This drainage element can be pulled in – resulting in minimal surface disruption.

And for push-up greens, PCD installation is accompanied with a 3/8th inch wide sand curtain to within 1 to 2 inches of the surface.

Water injection & a light rolling finishes the surface for return to play.

Slope (%)

Dis

sc

ha

rge

(G

PM

)

3/8th Core Manning's Equation Flow Capacity

0.2 0.3 0.40.5 0.7 1 2 3 4 5 6 7 8 910 200.02

0.03

0.04

0.05

0.07

0.1

0.2

0.3

0.4

0.5

We measured the flow capacity of the PCD element at a range of slopes to develop a flow capacity curve.

But how can a 3/8th inch core compete with a 2-inch pipe?

Hours of Drainage

Cu

mu

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ve

Dra

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e (g

al)

PCD DrainageFree Flow Only

0 4 8 12 16 20 240

50

100

150

200

25030 ft60 ft90 ft

Hours of Drainage

Cu

mu

lati

ve

Dra

ina

ge

(ga

l)Conventional Drainage

0 4 8 12 16 20 240

30

60

90

120

15030 ft60 ft90 ft

Drainage from 30, 60 and 90 ft of run for a conventional system reflect only the rate that water is moving to the pipe from the soil.

The 2-inch pipe never flows full.

Drainage from 30, 60 and 90 ft of a PCD system shows pipe capacity at 2% slope controlling flow at early times for 60 & 90 ft (the linear portion).

The 3/8th core flows full for early drainage.

Hours of Drainage

Cu

mu

lati

ve

Dra

inag

e (g

al)

PCD vs. Conventional at 90 ftFree Flow Only

0 4 8 12 16 20 240

50

100

150

200

250PCD (DS38)Conventional

Hours of Drainage

Cu

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rain

age

(gal

)PCD vs. Conventional at 60 ft

Free-Flow Only

0 4 8 12 16 20 240

25

50

75

100

125

150PCD (DS38)Conventional

Direct comparison of PCD and conventional systems shows equal drainage rates at 60 ft of run and nearly equal at 90 ft.

But because of the closer spacing of PCD, more water is removed overall.

And this analysis only considers free water flow in the PCD system.

The wettable fibers of the PCD element have a capillary attraction to water.

By installing the PCD element to create a hanging water column, I estimate that from 24 to 36 hours of drainage an additional 90 and 135 gallons would be removed for the 60 and 90 ft runs of the previous slide.

A demonstration of the hanging water column principle:

There are 3 principles that influence push-up greens drainage:

1) A sandy backfilled trench or sand curtain is required for adequate drainage.

2) Depth of drain placement is not very important when such a connection is used.

3) Closer spacing yields faster drainage and even small diameter conduits can adequately serve.

Any Questions?