Question
QUESTION: hi, we are considering putting in drains underground to drain off rainwater from two lawns that drain into our yard.  we have heard that they would only be viable for 5 years before getting clogged.  would it be better to put in the dry riverbed/ trenches with gravel instead?  we don't want to have to redo the work in a few years.
ANSWER: Open channels are always preferred over a closed pipe system, for ease of maintenance as well as the potential for clogging, as you've mentioned, especially if you are using drain-rock to help the water "go away".  If the pipes are big and the flow small, then you'll be able to have less work, and a longer drain service-life.  Of course, the entry/exit structures for larger pipes will be bigger & uglier, too.  They can (but don't always have to) involve large "headwalls" and such, to channel the water into the pipe, and "flares" to reduce the destructive force of concentrated waterflow exiting the pipe system - depends on how much water we're talking about.  

It also depends on how much and how far the water has to go for you to get rid of it.  Two "lawns" might not be a lot in a residential subdivision, but in the suburbs, it can be acres worth of a water-problem!

All this, to say that the "dry river" option has a lot more going for it, both in looks and in cost.  It, too, has its problems: mowing over rocks is a major pain, and there is nothing better for getting a dog (or kids) muddy.

If planned right, though, it will add to the landscape and create a wonderful amenity for you and the outdoor critters.

A word of caution, an open channel also become a major eye-sore if you just dump any old leftover rocks down and hope for the best.  It is like a sculpture: you are trying to mimic a natural system with irregular rock-sizes and a wandering pathway.  Don't try to "engineer" it, or you'd be better off with the pipe option.

The key to either option is to remember (lots of folks don't!) that "water flows downhill", and if there is a flat spot or a reversal of the grade, expect trouble.

Hope it helps ~Marc

---------- FOLLOW-UP ----------

QUESTION: thanks for that.  we were wondering about cost for the dry river.  do you know how expensive the rocks would be for that?  i am guessing good looking rock will be expensive.  are you talking about those rocks that are rounded like they have been in a stream?

Answer
They come in many sizes, and are pretty plentiful here (we're on the Truckee River), so the price is $26-28/yard for the small stuff (2" to 8"), and upwards of $50/yard for the big stuff (7" x 14").  Check with your local landscape bulk-supplier, and NOT Home Depot or you'll really pay a crazy price for the rock!

I don't even think they carry it here, in the land of large river rocks.  They have great prices on most everything else, just not large, bulk landscape materials, plus they sell them in cute little 2/cubic FOOT bags - thats 1/14th of a cubic YARD, so times their bag prices by 14 when thinking about equivalent cost ~!

You'll want a mix of sizes, for that "streambed" look (maybe some of those smaller stones can be purchased at Home Depot).  One yard will cover about 80-100 square feet, depending on how thick you lay them (3-4 inches, minimum), so a 3 foot wide by 27 feet long bed is 80 sf or about 1 yard of rock.

This is the local "delivered" price in my area, and usually a bit more (+$30/load) for fuel costs or a "short load" - anything under 10 yards, typically. Delivered means they dump it in your driveway, and you get to haul it to the final location!  And if you live in an area with NO source for these river rocks, you'll pay a premium...We get to pay through the nose for Arizona flagstone or Arkansas limestone; its only fair!

Some other tips:  Be sure and lay down some weed fabric, too.  It won't stop them from coming in, just slow them down for a year or two.  Remember that these rocks ADD thickness to the stream bed, so you may actually have to dig OUT some dirt to keep the same slope.  This can be used to add thickness to the sides of the bed, further "channeling" the water to the middle and away. It will look somewhat ragged for the first few seasons, but then the "growies" will soften the edges over time.

Good luck! ~Marc