Court Opinion

ID: 9558858
Source: CourtListenerOpinion
Date Created: 2023-08-21 17:18:01.679686+00
Date Added: 2024-06-11T09:09:38.570728
License: Public Domain

MOSK, J.
I concur in the holding and much of the reasoning of the majority. The majority correctly adopt the requirement that upstream and downstream riparian owners act reasonably, in the same manner in which the reasonableness requirement for the discharge of surface waters was explicitly recognized in Keys v. Romley (1966) 64 Cal.2d 396, 409-410 [50 Cal.Rptr. 273, 412 P.2d 529]. I write separately merely to clarify the issue of inverse condemnation liability with respect to the City of Lafayette (City) and the California Department of Transportation (Caltrans).
In this case, plaintiffs offered expert testimony that runoff from City streets, and from Highway 24 operated by Caltrans, was a substantial cause of increased flow of Reliez Creek and of the resultant flooding. Such evidence would ordinarily be significant enough for us to remand the case to the trial court for a full adjudication of the causation issue. However, as the majority rightly conclude, plaintiffs failed to prove the other elements necessary for making their case: that the public entities acted unreasonably, and that plaintiffs took reasonable measures to protect their own property.
The lack of such evidence of reasonableness in this particular case, however, should not mislead public entities. Today’s opinion, in adopting a reasonableness requirement for upstream riparian owners, and in reaffirming the cost-spreading rationale behind inverse condemnation liability, clearly puts public entities on notice that they are responsible for monitoring and mitigating the effects of the cumulative development of streets and highways on downstream riparian owners.
According to the principles enunciated by the majority today, downstream property owners would be able to prevail against a public entity in inverse condemnation liability if they are able to show: (1) that runoff from public streets and highways substantially contributed to the damage of the downstream owners’ property; (2) that the owners took reasonable measures to protect their own property; and (3) that the public entities responsible for the streets and highways failed to adopt reasonable measures to mitigate the foreseeable effects of such development. The precise meaning of “reasonable” mitigation measures in this context remains to be delineated on a case-by-case basis.
*379Nonetheless, the majority claim that they refrain from deciding “whether a riparian property owner who has altered the natural drainage has a continuing obligation to monitor the impact of the runoff from the property as urbanization occurs . . . (Maj. opn., ante, at p. 373.) It appears to follow inescapably from the principles of inverse condemnation liability reaffirmed by the majority, however, that when the riparian owner is a public entity, such an obligation to monitor does exist. Otherwise, downstream riparian owners would be compelled to pay a disproportionately high price for the cost of development of streets and highways in the form of damage to their property, and upstream public entities would be free of liability regardless of whether they could have taken reasonable mitigation measures to prevent foreseeable harm to downstream owners from cumulative development. Such a conclusion would be inconsistent with the cost-spreading rationale of inverse condemnation liability. (See Holz v. Superior Court (1970) 3 Cal.3d 296, 303 [90 Cal.Rptr. 345, 475 P.2d 441].) Nothing in the majority opinion should be interpreted to suggest the contrary.
Appellants’ petition for a rehearing was denied April 13, 1994.