How do I improve the drainage in my yard?

April 3, 2015

Spring is so beautiful in the Northwest.

As we watch our gardens awaken for spring we also welcome spring rains and Northwest drainage issues become much more evident. Storms become more frequent and the lower temperatures aren’t very conducive for evaporation. Areas with poor drainage struggle to recover after each storm. Proper drainage is very important in the Northwest.

Magnolia- Bellevue Botanical Gardens -Sublime Garden Design

Magnolia- Bellevue Botanical Gardens -Sublime Garden Design

The key elements of good drainage for any landscape are:

  1. Good soil
  2. Appropriate slopes
  3. Plant material
  4. An adequate exit or storage space for excess runoff

Good soil is the foundation of any garden. A healthy rich soil feeds the plants and organisms and also provides for a sustained water holding capacity. The depth of the soil is also very important. The deeper the soil before hitting hard pan the less drainage issues you will have. Soils with more organic mater (think rich black compost… mmmmm) will soak up water and hold it longer than soil lacking organic mater.

Dark, rich compost

Dark, rich compost

The slope of the site, or lay of the land, will determine where the water will go and how fast. A gradual slope will allow water to penetrate the soil as it moves, a steeper slope will increase the flow and not allow for as much water to penetrate. Some slope even if gradual is still very important. Flat ground is not good for drainage, the water will sit with nowhere to go. Even ‘flat’ lawn areas when installed properly should have some slope to them. All impervious surfaces (ie: patios) MUST have a slope. Directing the slops in your yard to direct the water purposefully will really give you the upper hand on drainage. Establishing appropriate ‘low spots’ away from high use areas will allow you to enjoy your garden even through the winter.

photo: Rain Garden Handbook for Western Washington - WSU Extension

photo: Rain Garden Handbook for Western Washington – WSU Extension

Plant material plays a key role in drainage because established root systems will help take up a good portion of the water soaking into the ground. There are plants that are water lovers that will soak up even more water than the average plant that can be beneficial for really soggy areas. These plants have created their own design trend – Rain Gardens. That is a topic for another day though.

Acorus gramineus 'Ogon'

Acorus gramineus ‘Ogon’

Water conveyance is the last but not least consideration to proper drainage. Water is lazy and will always take the path of least resistance flowing downhill to the lowest point and though the softest soils.  Once the slopes have been planned and coordinated to create a natural path  for the water to flow the next step is to plan for overflow. We live in the Northwest after all. When we get large storms or repeated wet weather  the water needs to be given a good direction to overflow. Ideally all storm-water should be allowed to soak into the land where it falls but that isn’t always possible.

As the rain falls outside take a look at the problem areas in your yard to see what elements of good drainage are missing or could be improved on.

~ Kryssie

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