The Civil Code of Québec states that natural runoff water from higher land must be able to flow freely onto lower land.
As a result, if you are the owner of lower land, you cannot build any kind of structure to prevent natural runoff.
Conversely, if you own higher land, you cannot do anything to aggravate the condition of lower land, and you are not presumed to do so if you carry out:
work designed to facilitate runoff along its natural slope;
drainage work, if your land is used for farming.
If you own a building, you must make sure that water, snow or ice from your roof falls onto your land only, and not ontp your neighbour’s land. Where necessary, your neighbour may force you to install a snowguard or eavestrough to keep snow and water on your side of the boundary.