French Drains for Torrential Rains

Much of my deer resistant garden is on a slope. The slope was created by the construction of the house in 2005. While the builder tried to minimize the damage, the heavy machinery access required some scraping away of the topsoil as it turned and twisted to create a level building envelope. We were left with hard-packed white dirt that wouldn't grow anything.

Had the slope grown grass (we tried), there might never have been a large garden on the slope.

Dump truck loads of good garden soil were delivered. The garden slopes down to the house. In 2007, when I began planting the gardens, I created an edging trench in the form of a small French drain (rock below the grass) at the top of the slopes to separate meadow from garden.

That worked well, but there was the occasional garden erosion during heavy rains.

In November 2009, I once again began cutting out a nice, sharp garden edge between the small, hidden drain of rock and the garden until...

My husband decided that we should add concrete edging. We did. But, the torrential rains came before the grass could grow over the backfill soil!

The small rock and the soil washed downhill with the series of winter rains. The garden had significant erosion and 8,000 poppy seeds were relocated somewhere outside the garden!

In February, we tackled the drainage issues again.

This time, we dug the trench out one foot wide and deep. We laid a 4 inch perforated pipe, covered in a sock to keep the soil out. We added sharp drainage rock where the pieces are one to two inches in size. On top of the drainage rock, we added more expensive decorative round rock.

A true French drain wouldn't have the pipe, just rock. But, we took liberties with the definition of a French drain to ensure that we won't have to redo the project again!

Since the French drain was completed, we've had several more torrential rains. There was no erosion at all. An added benefit is that the decorative rock packed down firmly on top of the sharp rock. The rock is stable enough for rolling a wheelbarrow and wide enough for one person to use as a garden path—and the lawn mower can clear the rock to mow the grass.

Sometimes, you do things three times before you get it right!



This article describes how we handled our drainage issues. We are not experts on drainage systems. Words and photos by Freda Cameron, Defining Your Home, Garden and Travel.