natural runoff
In French: écoulement naturel des eaux
Definition
Water that flows by itself from higher land to lower land. The lower neighbour must receive it, but the upper owner may not make things worse by concentrating or redirecting water toward them.
Sources
The Quebec government summarizes Civil Code article 979: lower land receives natural runoff and the upper owner may not make it worse. (C.c.Q. art. 979)
Écoulement des eaux (rapports de voisinage) · Gouvernement du Québec