View Full Version : Drainage swale

08-27-2002, 06:42 PM
We are working on a soccer field, on one side is a new drainage swale it handles all the run off for the entire park (18 acres). We installed a erosion control blanket in the bottom of the swale but with the last rain we lost everything! I mean blanket, seed dirt......

The blanket failed noted by the fragments of blanket left along the way. The swale is 700' long but only the bottom 6' is gone.

Any Ideas to solve this delema?

08-27-2002, 07:12 PM
Is there a way to slow the water down? Could it be less steep toward the outlet end or could there be stone or other material to slow down the water at least periodically?
Maybe there could be a detention pond?
Eighteen acres is a lot of runoff area. Was this designed by an engineer?
Those are the questions that I would ask.

08-27-2002, 07:25 PM
It was designed by an engineer, the LA posted in the contract documents that all straw bales be removed when seeding completed. Here's the tough part at the begining of the swale are 2 24" RCP pipes with precast FES. Water backs up but increases the velocity of the water. Swale ends up at a small creek so water quality is a major issue. TRMs maybe?

08-27-2002, 08:08 PM
This wouldn't happen to be the Fox Cities project, would it? And if it is, could it be at USA sports complex? I believe I saw them expanding the # of soccer fields they have.

As for your dilemma, FES and TRM are GREK to me. Straw bales would've been my input, but it looks like that's out (unless the LA can be turned around). Did you use turf staples throughout the blanket?

How about big roll sod stapled down?

08-27-2002, 08:33 PM
FES= Flaired End Sections
TRM= Turf Renforcment Mat

Staples were placed 18" apart for high flow areas.
the water moved the erosion blanket and dirt.

08-27-2002, 09:41 PM

soil erosion is affected by many factors such as a soil's texture, structure, slope, surface roughness, and soil cover. Slope actually has two components:grade and length. With a 700 foot length even a minor grade allows water to accelerate at the bottom of your swale and errode the swale. Have you thought of terracing the swale to reduce the effective length of the swale and slow the water? What is the % grade of the swale's slope?


08-27-2002, 11:24 PM
the grade is less than 1%

08-27-2002, 11:33 PM
I'm wondering if straw or coir wattles secured with wooden stakes across the swale in several places on the lower end would slow down the flow enough to prevent the scouring effect of the water flow. Surely Erosion Control Mag. has something that will be just right.

08-28-2002, 12:10 AM
We are looking for a solution that will allow the water to flow without stopping it and killing the any seed, now I know that 100% coverage might not be possible. this swale was going to be mantained once or twice a year ( a slow growing fescue mix) was used to seed it. The over all effect was to allow the roots of the grass to renforce the the soil and allow water to flow over it.

Main problem volume of water. even small rains at this point are a problem because no turf is able to become established.

Soils, this area of the site has had a heavy amount of dirt moved to allow the field to be playable (leveled), under the top soil (6") is heavy clay/topsoil mix but compacted by heavy equipment.

Elevation changes, the park has over 20' of elevation change by the time it starts this 700' >1% swale.

08-28-2002, 07:43 AM
Plant wheat with your grass. Wheat germinates quickly and roots dramatically. Next spring before any mowing, wheat will be high above desireable grasses, then wick wheat with Roundup. Or just wait for wheat to die in summer; but that would require more mowing.

Not sure of density to plant. I might be able to find out from an oldtimer nearby if you want the info. Wheat was used in seeding, for soil stabilization, until the 1920s. Its upright growth allows light for the desireable grasses.

Pic is wheat 3-4 days after seed hits the ground. That's a quarter in the middle.

08-28-2002, 05:49 PM
We didn't get one day out of the straw netting, installed that day and rained that night. 6" to 18" of topsoil and clay washed out.

Met with my geo fabric supplier and blanket manufactor rep today.....

Here's what they are looking into. Install a gabion blanket 16' X 8'X 6" thick at the outfall, then install a soil filled TRM 12.5' wide along the bottom of the swale. Install removable checks along the swale. These will be triangler silt dikes.

Now the reason why we are going this route, water will be flowing thru the area most if not all the time, the roots of the grass will grow thru the TRM and reinforce the soil and provide shear strength so the soil under it will not wash out.

Only question left is the type of stapes to use or wood pegs.

08-28-2002, 09:39 PM

Correct me if I'm wrong but aren't we looking at an approximate 3% grade?

Not trying to be a smart a** or anything just making sure the numbers make sense



08-28-2002, 10:08 PM
No the elevation change BEFORE the swale is 20' . the elevation of the top of the swale is 734 at the bottom is 727 the actual lenght of the swale is 768' long with a 7' drop.

08-30-2002, 09:12 PM
Turfquip/Paul....I have got to ask you man, what in the hell is that thing you have in the pic? My monitor isn't the best in the world which as it were gives me the apperance of an albino catfish, frog or something from Si-Fi. :confused:

08-30-2002, 09:29 PM
It's a picture of 3 day old wheat

08-31-2002, 07:28 AM

It's a pi**ed off mole

Moles DO bite you know....

09-02-2002, 12:23 AM
if it is not too near the playing area you could use fist sized stone or a little larger piled across the swale in a dam formation. thicker at the bottom thinner at the top. do this a serveral intervals,75 to 100 feet apart. i have seen this done along some roads to slow water down.

you plant it, I'll maintain it

09-02-2002, 11:33 AM
Don'r really have any advice for you, but wanted to drop in and say Hi!

Good Luck with your swale!! Looks like you got your hands full there partner!

Let us know how it turns out Paul.

09-03-2002, 12:14 AM
Re-ammending the contract would be the first step.

Temp silt fence would be a solution untill the grass has had adiquate time to root.

Anything to slow the water down. Those pipes feeding this swale speed the water up and cause the erosion, it will always erode until the water speed has been slowed.

How much extra are they willing to spend on this?

Those TerraCell's would be the unlimate solution for the bottom of the swale only. I guess this is similar to what you have planned.