November 2020 – Law and Civil Engineering

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Be Aware If Your Plan Increases Surface Water Runoff
by Eugene Bass

An adjoining land owner made some improvements to their property that changed the surface water drainage patterns. The improved land was slightly higher and after the improvements were completed, the downslope neighbor experienced flooding of a walkway adjacent to the common property line.

An expert hired by the downslope owner concluded that the improvements by the up-slope owner changed the surface water drainage of the property to reverse the original direction of flow from the rear to the front of the lot and to increase the amount of runoff onto the down-slope property. The down-slope owner sued the neighbor for damages resulting from the increased flow. The resulting case recited the various rules applicable to liability for damages resulting from runoff of surface waters.

Surface waters are defined as water diffused over the surface of land and resulting from rain, distinguishable from water flowing in a fixed channel or identifiable body, such as a river or lake. It is the general rule that the owner of an up-slope property is entitled to discharge surface water from his land as the water naturally flows. The rule has been defined and interpreted by the courts, however, to attempt to remain applicable to increased urbanization.

When an up-slope owner does something that results in increased surface water flow onto a down-slope property, the down-slope owner is required to follow reasonable conduct, under the circumstances. The social utility of the upper owner’s conduct will be weighed against the burden that such conduct imposes on the lower owner. The courts have not said that an upper owner cannot do anything that would result in increased runoff but have sought to realistically deal with the normal increases in surface water runoff that results from urbanization.

In determining liability of an upper owner to a lower owner, the courts have defined certain rules. It is incumbent upon every person to take reasonable care in using his property to avoid injury to adjacent property through the flow of surface waters. Failure to exercise reasonable care may result in liability by an upper to a lower landowner. An upper landowner is liable to a lower landowner where there is a discharge resulting in damage to the property of a reasonable lower landowner: (1) if the upper owner is reasonable and the lower owner is unreasonable, the upper owner wins; (2) if the upper owner is unreasonable and the lower owner is reasonable, the lower owner wins; (3) if both the upper and lower owners are reasonable the, the lower owner wins. An upper landowner may not avoid liability to a lower landowner by showing that a lower landowner was unreasonable simply for failing to take affirmative action to prevent the flow of surface waters onto his or her property. And, where the lower landowner acts reasonably, by action to minimize the damage, or by inaction which does not unreasonable increase his damages, the upper landowner is liable for the lower landowner’s damage.

The laws relating to liability for increased surface water runoff need to be considered in the development of civil engineering plans that affect the flow of surface waters.

This article is intended only to provide general information regarding legal issues. It is not to be relied upon for legal advice. Contact your attorney for advise and guidance on general and specific legal issues.

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