Water drainage generally includes the movement of surface water and often becomes a legal issue when the surface water causes erosion or other damage to a landowner’s property. A landowner (neighbor) or a homeowner’s association (HOA) responsible for common area maintenance from which the water moved or drained is generally not responsible for damage to a landowner’s property if the water movement, drainage, or runoff is caused by naturally occurring rain and land conditions.

But if the landowner or HOA landscaped or changed its property (such as with a berm) in a way that caused more water to run on another landowner’s property or to move or erode soil and damage another landowner’s property, the landowner or HOA that made the changes may be liable for the damage.

Laws vary from state to state but there are three legal rules courts may apply in determining whether a landowner or HOA that alters the drainage or runoff of water on its property is liable for damage to another landowner’s property caused by the drainage or runoff:

• Reasonable Use Rule—The reasonable use rule generally allows a landowner or HOA, for example, to make reasonable alterations to the drainage patterns on their property and to avoid liability for damage caused by the resulting water drainage or runoff—unless the altered drainage or runoff pattern causes unreasonable harm to adjoining or nearby landowners. In determining whether the alteration was reasonable courts consider factors such as: (1) whether there was a reasonable necessity for the landowner to make the alteration to make use of their land; (2) whether the alteration was done in a reasonable manner; (3) whether the utility, usefulness, or increased value of the landowner’s property outweighs the damage done to other properties; and (4) whether the damage to the adjoining or nearby property owners was reasonably foreseeable to the landowner or HOA that altered the drainage or runoff pattern.

• Common Enemy Rule—The Common Enemy Rule treats rainwater and other natural sources of groundwater as a common enemy of all landowners and allows each landowner to protect their land from surface and runoff water. If a landowner is adversely affected by another landowner’s alterations, the adversely-affected landowner must make their own alterations to address any resulting property damage. Some states that apply the Common Enemy Rule have modified it to make a landowner or HOA that negligently makes alterations to its property liable to a landowner whose property is damaged or diminished in value.

• Civil Law Rule—The Civil Law Rule—also known as the Natural Flow Rule—is the opposite of the Common Enemy Rule and makes any landowner who alters their land in a way that changes the natural flow of surface water liable to another landowner whose property is damaged as a result of the alteration. Some states that apply the Civil Law Rule have modified it to allow a landowner to alter their property without liability to another landowner if the alteration is reasonable.

In Alaska, the regulation of water drainage and liability for property damage caused by alterations in water flow is not governed by a specific statute but rather by common law principles, which are court-made laws derived from precedent. The state generally follows a modified version of the Reasonable Use Rule. This rule allows a landowner or homeowners' association (HOA) to make reasonable alterations to their property, including changes to drainage patterns, without being liable for any resulting water drainage or runoff damage to another's property, unless the alterations cause unreasonable harm. When determining reasonableness, Alaska courts may consider factors such as the necessity of the alteration, the manner in which it was done, the benefits to the altering landowner's property versus the damage to others, and the foreseeability of the damage. Alaska does not strictly adhere to the Common Enemy Rule or the Civil Law Rule, but the principles of these rules may influence court decisions, particularly in terms of negligence and the reasonableness of alterations. It is important for landowners and HOAs to consider the potential impact of their property alterations on neighboring properties and to consult with an attorney if they are planning significant changes that may affect water drainage.