A drainage easement is an attachment to a property deed which states that access to part of the property is given to a third party, usually a municipality, for the purpose of maintaining drainage. The drainage easement may include a culvert or drain which feeds into a drainage system or the easement may simply state that runoff needs to be allowed to flow freely over an area of the property. The easement cannot be lifted from the deed unless there are special circumstances, and it will be associated with the deed even when it is transferred or sold.

Easements in general are used to address cases in which someone other than the property owner needs the right to access the property, and the easement comes with the right to use, but not full ownership rights. Another common example of an easement is a road easement, in which part of a property is used for a shared or even public road and an easement protects the rights of others to use that road. Easements are drafted by lawyers who work with the property owner and the parties who need access to ensure that the document is accurate and fair.

In the case of a drainage easement, the easement benefits the property owner as much as it benefits anyone else. In order for a municipal drainage system to work effectively, the municipality needs to ensure that drainage easements are in place so that city workers can access private property in order to maintain and repair drainage areas. For example, if a culvert runs through a property, the drainage easement allows the city to replace it if it is damaged.

If the drainage system does not work properly, the property owner can be at risk of flooding and other problems. In exchange for allowing the municipality to access the property, the property owner gets to enjoy a property which drains freely, and knows that neighbors are also obliged to maintain their drainage easements to ensure that water intrusion will not occur along the property line.

When a drainage easement is in place, there are restrictions on how the easement area can be used. People usually cannot regrade the soil or build structures because this could impede the free flow of water over the property. If there is a culvert or pipe, trees cannot be planted over it, because their roots could block it, and people are expected to keep gratings clear so that the water can drain properly. If people would like to change the terms of the easement, they must reach an agreement with the agency which holds the easement.