## Facts

- Crest operated an automobile dealership on a parcel in Delavan, Wisconsin; the adjoining parcel to the west was owned by Willemsen/A.O. Bauer Glass, Inc.
- Before 1979, the Bauer Glass parcel lay at a lower elevation than Crest’s parcel, and surface water historically flowed from Crest’s parcel onto Bauer Glass’s parcel and then dissipated or drained off to the north/northwest.
- Willemsen purchased the Bauer Glass parcel knowing it was low relative to land to the east and that surface water tended to accumulate on it.
- Willemsen placed substantial fill on the Bauer Glass parcel, raising its elevation above Crest’s parcel and reversing the prior drainage pattern.
- Willemsen installed a private storm sewer system on the Bauer Glass parcel connected to the municipal storm sewer (about $68,348.94).
- Willemsen urged Crest to connect to the municipal storm sewer (estimated about $9,000 at the time) and warned that otherwise diverted water would back up onto Crest’s property.
- Crest did not connect immediately; after the elevation change and improvements, surface water accumulated on Crest’s property and caused flooding damage.
- Crest sought about $4,500 in property damage and $11,620 for the cost of connecting to the municipal system, alleging a private nuisance from unreasonable diversion of surface water.

## Issues

1. Whether the defendants’ land alterations unreasonably diverted surface water onto Crest’s property under Wisconsin’s reasonable-use doctrine for surface water, creating liability in private nuisance.
2. Whether Crest’s failure to promptly connect to the municipal storm sewer constituted an unreasonable failure to mitigate damages barring or reducing recovery.

## Decision

- The Wisconsin Supreme Court affirmed the court of appeals.
- The court held the defendants acted unreasonably by altering elevation and drainage in a way that diverted and accumulated surface water on Crest’s parcel, creating a private nuisance and liability for resulting harm.
- The court held mitigation principles apply in nuisance cases, but Crest did not respond unreasonably by declining to immediately incur the cost of a sewer connection.
- The defendants were liable for $16,120 in damages, including flooding damage and the cost of the sewer connection.

## Legal Principles

- Wisconsin applies a reasonable-use standard to surface-water disputes; liability turns on whether the landowner’s conduct causing interference with another’s land is unreasonable under all the circumstances.
- In determining unreasonableness in a surface-water nuisance case, courts balance the gravity of harm against the utility of the actor’s conduct, including foreseeability, the extent of harm, and feasibility of avoiding or reducing harm.
- A landowner who materially alters natural drainage and thereby causes an unreasonable interference with a neighbor’s use and enjoyment of land may be liable in private nuisance.
- An injured party generally must take reasonable steps to avoid avoidable consequences (mitigation), but mitigation does not require unreasonable expenditures or shifting the cost of an intentional nuisance from the creator to the victim absent unreasonable inaction.
- Where a defendant’s unreasonable diversion makes protective measures necessary, the reasonable cost of those measures may be awarded as damages.

## Conclusion

The court held that a landowner who raises and improves property in a manner that reverses natural drainage and causes surface water to accumulate on a neighbor’s land commits an unreasonable interference under the reasonable-use nuisance doctrine, and the neighbor’s recovery is not reduced absent an unreasonable failure to mitigate.


Crest Chevrolet-Oldsmobile-Cadillac, Inc. v. Willemsen, 384 N.W.2d 692 (Wis. 1986)