I recently had a landscaping company install a mortared-stone drainage flume on the interior of a retaining wall at my house:

Drainage Flume

It looks great and works just as well. It naturally has me wondering ... On the other side of my house, there is a natural water flow since the back of our house butts up to a rather substantial hill:

Potential site

The head of the arrow shows the opening to which the water flows. For reference, we had about two inches of water flowing across the path of the arrow this morning after a thunderstorm.

My idea: I want to build a drainage flume/sidewalk. The thought is the center would be about 12" with 6" sides sloped up about an inch. (For the cross-section, it would be equivalent to about a 5" pipe.) The length of run is about 45'. Also, there is already sufficient slope of drainage.

So, my questions are:

  1. Is there anything I am missing about this that would make it a bad idea?
  2. How deep of a footer would I need to pour? The heaviest thing that will ever cross is my riding lawn-mower (~1000 lb)
  • The 5" pipe reference is to indicate how much water it could transfer. I might be using the wrong terminology. I imagine prior to putting the stone on top of the ground, it would need a sturdy concrete base on which it would rest. If I wasn't driving my mower over it, I would think I would just put the stone in mortar straight on the soil. I'm afraid the mower may crack it otherwise. – NoClue Aug 8 '17 at 23:09
  • The thickness of the footer will depend on the base material. Packed crushed rock will reduce the thickness. I would have at least 3" to prevent / reduce cracking from driving on with your mower. – Ed Beal Aug 9 '17 at 13:42

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