If you are planning a deck for entertaining or modifying the garden with retaining walls you need to think about protecting your family, and guests.
You can do a lot of damage with a fall from from a relatively low height.
If someone falls and you haven’t provided appropriate barriers you could be personally liable and the insurance company has the opportunity to avoid paying compensation.
National Construction Code
Here is a summary of the current regulations on protecting from falls:
Where people could fall 1 m from a floor, or through an opening a barrier must be provided.
The barrier must be continuous and extend for the full extent of the hazard; and be high enough to protect people from accidentally falling
The construction shall prevent people from falling through the barrier, including small children, and should be strong enough to withstand thee impact of people; and the pressure of people pressing against it.