Raised bed drainage issues

(Question)

Hello!
So I was building my first raised bed ever and I’m placing it in my back yard. Issue is when it rains my yard floods a bit and I was wondering if that will negatively affect my raised bed. I was planning to line the bottom with cardboard but should I use something more sturdy to separate my new soil from the dirt underneath? Also there seems to be long periods of rain in my city (Toronto) so what should I do to prevent damage to my future garden. Thank you so much in advance!

(Answer)

Congratulations on your project – it is very rewarding to grow your own food.

As a future reference for you, there is a wealth on information regarding raised beds available on the Toronto Master Gardeners website.  If you type “raised beds” in the box under the Find it Here heading on the right side of the screen, you will be able to read all previous questions and answers related to this topic.

From the photo you included, it appears your bed will be in a low lying area in your yard which is prone to being very wet.  You did not indicate how deep you plan to build your bed or what you plan to grow in there.  If vegetables are your choice, the minimum depth for edibles is 8″ – 12″.  Also, adding organic matter such as leaves and compost as well as some shredded up newspaper will facilitate drainage.  Opinions are mixed regarding the addition of crushed granite or pea gravel to the bottom of the bed, so I would suggest you resist going this route.

https://www.selfsufficientme.com/fruit-vegetables/how-much-drainage-and-soil-do-i-need-in-a-raised-garden-bed

A second alternative is to build an elevated raised garden bed as illustrated in the following website:

https://savvygardening.com/elevated-raised-bed-gardening/

Good luck.