Question
Dear S.D.
I just bought a new house in Katy, the back yard lawn app. size of 24 x 55 ft. The lawn has a drainage system, with some drain holes in the middle of the lawn, and it has almost like 'deep trench' a spread across the 55 ft long yard. While I understand for Slope required for good drainage, but there also has to be a good balance of a 'flat' lawn to enjoy. Is there any guide line of how much slope minimum required for a good drainage?
Thank you for your expert advise.

Iwan Chandra

Answer
Iwan,

Thank you for your patience in me getting back with you.

Concerning your drainage issue, there are some considerations to give towards your problem. The first is the type of soil. The more dense the soil is, the more important your slope is. Concrete for instance requires a 2-3 degree slope to insure that water drains. In such situations where you have a dense soil or ground that has a shallow hard pan just below the surface, a slop of as much as 10 degrees to a drain which can take the water away from the area is needed to unsure that you do not have continually wet top ground/turf.

The next would be the permeability of the existing soil. If you could increase the permeability of the soil you can reduce the slope of your lawn towards the drains, whereby increasing the functionability of your lawn. This can be resolved by roto-tilling up the soil and adding sand and other organic matter.

You can also consider installing French drains throughout your yard to catch the water and take it to a low point in lawn. If you use this approach, you can take the water to the back of the lawn (and if appropriate, to a water feature of some sort that can complement your landscape. We have done this on several occasions for homeowners with similar needs for effective drainage of their lawn while enhancing it functionability for recreation.

I hope this information is helpful. Please do contact me again if you need any further insight or encouragement in addressing this problem. I will attempt to be more diligent in getting back with you, but until I am no longer having to be at the hospital (no Internet access), it may take a few days. Thanks again for your patience.

In the garden,

David Ward