Source: https://www.berliner.com/article/responsible-uphill-stormwater-causes-downhill-damage/
Timestamp: 2019-04-22 04:33:30+00:00

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But what if the measures you take to prevent stormwater damage to your property negatively impact your downhill neighbor? In many cases, the uphill landowner will be liable for any actual damages he or she causes downstream.
General Rule: An uphill landowner is liable for damages caused to downhill property resulting from surface water that the uphill owner alters from its natural course, unless the downhill owner acts unreasonably.
However, if both the uphill and the downhill landowners have acted reasonably, the uphill owner will be liable.3 This analysis is referred to as the “modified civil rule,” and it is a rule of negligence, as opposed to a property law-type rule like trespass.4 If a lawsuit ensues and a court finds the uphill owner to be liable, he/she may be ordered to fix the problem, pay the costs of correcting any actual damage caused, and/or compensate the downhill owner for any depreciation in value caused to the downhill property.
The question of reasonableness of conduct considers both the actor’s interest and the effects of the actor’s conduct upon others. It is a question of fact to be determined on a case-by-case basis, considering factors such as the amount of harm caused, the foreseeability of the harm which resulted, and the purpose or motive with which the landowner acted.5 The question of the parties’ reasonableness may get complicated depending on the specific factual scenario. For example: when there are multiple sources of uphill stormwater, when the stormwater discharge was planned or engineered not by the uphill owner but by his/her contractor, when the uphill owner was protecting his or her property from uphill, collected stormwater, or when the damage was the result of an “Act of God” (which is other than simply heavy rain).
Public Entity Liability: A public entity can be liable for negligence or inverse condemnation for stormwater discharges from a public improvement.
Has the discharger acquired a prescriptive drainage easement?
In exercising that discretion, and in weighing the relative hardships, the court should consider various factors. It starts with the premise that defendant is a wrongdoer, and that plaintiff’s property has been occupied. Thus, doubtful cases should be decided in favor of the plaintiff.
1. Defendants must be innocent – the encroachment must not be the result of defendant’s willful act, and perhaps not the result of defendant’s negligence. In this same connection the court should weigh plaintiff’s conduct to ascertain if he is in any way responsible for the situation.
2. If plaintiff will suffer irreparable injury by the encroachment, the injunction should be granted regardless of the injury to defendant, except, perhaps, where the rights of the public will be adversely affected.
Was the water problem the result of the uphill landowner(s) changing the natural course of surface water (stormwater)?
Was the upper owner’s conduct reasonable, considered in relation to potential impacts on your property?
Did you do anything to contribute to the damages? Is there some action you could have taken to prevent or minimize the damages, but chose not to do? Why/why not?
When did you actually discover the water problem? Would a reasonable person have discovered it earlier?
Was the source of the collected stormwater an uphill structure that is owned or maintained by a public entity?
Was the natural flow of surface water altered not by the uphill landowner, but by his/her contractor?
Does the uphill owner have a drainage easement across your property?
Do facts exist to support all elements of the uphill owner’s prescriptive easement claim?
It is important to be mindful about how you alter the natural surface flow of stormwater and what impacts the discharge of that stormwater may have on downhill property. Liability for accidental property damage can be avoided by implementing a responsible stormwater plan, or cooperating with your neighbors in developing a joint stormwater plan. If the uphill property owner is collecting and discharging stormwater without regard to its downhill impacts, then the law would generally hold the uphill owner responsible for any damages caused. Note that homeowners’ insurance policies may not cover either the uphill owner or the downhill owner for these types of man-made damages.
Finally, whether or not the stormwater discharge involves damages to the downhill property, the parties may dispute the uphill owner’s legal right to discharge stormwater through the downhill neighbor’s property under a prescriptive right theory. These issues can be complicated and expensive to resolve in court if there are many factual issues in dispute.
1 Keys v. Romley(1966) 64 Cal.2d 396, 405-06.
4 The downhill plaintiff may also have causes of action for nuisance and/or trespass, although those topics are beyond the scope of this article.
5 Keys v. Romley, supra, 64 Cal.2d at 409.
6 Locklin v. City of Lafayette(1994) 7 Cal.4th 327, 368.
7 Skoumbas v. City of Orinda(2008) 165 Cal. App. 4th 783, 792-93; See also Locklin v. City of Lafayette, supra.
8See Hails v. Martz (1946) 28 Cal.2d 775; Field-Escandon v. Demann (1988) 204 Cal.App.3d 228, 235; Hahn v. Curtis (1946) 73 Cal.App.2d 382, 385-86.
9Field-Escandon v. Demann, supra, at 238. See also Warsaw v. Chicago Metallic Ceilings, Inc. (1984) 35 Cal.3d 564.

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