Good Trenches Make Good Neighbors? A Brief Primer on Neighbors’ Rain Runoff

As you’ve surely noticed, there’s been a lot of rain in San Diego, and in California in general, this year. One of the issues all this water causes are neighbor disputes about runoff from one property to another. Someone called me the other day about exactly that, and the fact that rainwater from an uphill neighbor’s property had flooded the ground floor of this poor guy’s house during a particularly heavy deluge. He wanted to know what his rights were.

Generally, the rule in California depends on the condition of the neighbor’s property, and a recent case on the issue is Contra Costa County v. Pinole Point Properties, LLC, (2015) 235 Cal.App.4th 914. Summarized, the law is that if the uphill property is in its natural condition then the excess water is a “common enemy” and it’s the downhill property owner’s problem. But if the uphill property has been altered, then the rule of reasonability controls. Both the uphill owner and the downhill owner must take reasonable steps to mitigate the flow, and if the downhill owner is still unhappy then he or she will sue, and then the parties will argue over (and maybe ultimately go to trial on) what constitutes “reasonable.” Unfortunately, there’s no bright line rule on what’s reasonable versus unreasonable, and it comes down to a case-by-case analysis of the respective properties’ facts.

Let me know if you need help dealing with a neighbor and water, and we’ll work together to figure out how best to handle it. If I can’t help you then I’ve got a great network that includes real estate litigators with experience in such disputes.

Greg Borman is an attorney in San Diego, California, who advises and represents businesses of all sizes and stages, as well as their owners.  He can be reached at or at (858) 232-7100.

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