Can My Neighbor Drain Water Onto My Property? Runoff Laws by State

The two questions that decide most cases

1. Did someone change how the water arrives? Water that crosses the line as a broad sheet, the way the land has always sent it, is natural flow. Courts in nearly every state treat it as part of owning lower ground. Water that now arrives at a point, faster, or in places it never used to — after a neighbor added a downspout outlet, a pipe, fill, a patio, a regraded lawn or a ditch — has been altered, and that is where liability is possible.

2. Which rule does your state use for the change? That decides how a court weighs it:

• Reasonable use (20 states) — Each owner may make reasonable use of their land, even if that changes how surface water flows, but is liable when the interference is unreasonable — courts weigh the purpose and benefit of the change against the harm it causes the neighbor.
• Modified common enemy (11 states) — Surface water is treated as a 'common enemy' every owner may fend off, but with limits: no needless or careless harm, and generally no collecting water and discharging it onto a neighbor in a concentrated flow.
• Civil law (natural flow) (15 states) — Lower land must accept water that flows naturally from higher land, and an owner who changes that natural flow to a neighbor's injury can be liable. Some states soften it, for example for reasonable improvements or normal farming.
• Mixed rule (2 states) — The state's courts apply different rules in different settings, for example one rule for farmland and another for town lots. The state card explains which applies where.

The labels matter less than they seem. Courts under all three main rules have held owners liable for collecting water and discharging it onto a neighbor through an artificial channel. In New York, a modified common enemy state, good-faith improvements are allowed but draining onto a neighbor by pipes, drains or ditches is not. Texas puts it in a statute (Texas Water Code § 11.086). New Jersey's Armstrong v. Francis Corp. (1956), the case most reasonable-use states follow, asks whether the change was reasonable given its purpose and the harm.

Two states split by setting: Alabama applies the civil-law rule outside city limits and a modified common-enemy rule inside them and South Dakota uses the civil-law rule for rural land and reasonable use for urban land.

What to do, step by step

1. Work out whether it is natural or altered flow. Has anything changed on their side, and does the water arrive at a point or along a line? Our neighbor runoff guide walks through the test.
2. Document it during rain. Video showing where water crosses the line, with a fixed reference such as a fence post; dated photos of pooling, erosion and damage over several storms; photos of the source from your side (a pipe end, a downspout, new fill); and a note of when it started and what changed around then.
3. Talk to the neighbor, then follow up in writing. Many owners don't know where their downspout or drain sends water. A short, friendly note afterwards creates a dated record that they were told.
4. Check your city or county rules. Look up the stormwater, grading or downspout section of the municipal code, or call the stormwater or code enforcement office. Some examples we verified are below. An ordinance breach can be enforced by the city without a lawsuit.
5. Check the HOA documents and your plat. Covenants, recorded drainage easements and the approved grading plan for a subdivision can decide who may send water where.
6. Try mediation. Many counties run community mediation centers for neighbor disputes, and a shared fix such as a swale along the line, written down, is often cheaper than either side's legal bill.
7. See an attorney when it matters. If there is damage to a foundation, basement or structure, the neighbor won't engage, or you're weighing a claim, talk to a local real estate or property attorney. Time limits for property-damage claims vary by state and can be short.

Meanwhile, fixes on your own side of the line — a swale or berm, an interceptor French drain, or regrading — can stop the damage while the conversation happens. Avoid simply damming the water back toward the neighbor: under several of these rules that can make you the one who altered the flow.

What the 50-state check found

• No verified state lets a neighbor do anything at all with surface water. Of the 48 states we verified, every one limits how an owner may alter the flow onto a neighbor.
• Reasonable use is the most common rule (20 states), followed by the civil-law rule (15) and the modified common-enemy rule (11).
• Several states changed rules in the last 70 years, most toward reasonable use: North Carolina in 1977, Missouri in 1993, Wisconsin in 1974 and West Virginia in 1989, among others.
• 38 states are high confidence, read in the opinion or statute and stated expressly there. The rest rest on older cases or need a later case to confirm them, and their cards say so.
• Two not verified (Kansas and Wyoming): we could not confirm their current rule, so we left the doctrine blank rather than guess.

How we researched this, and its limits

• Primary sources first. For each state we looked for the court opinion that adopted or most recently restated the rule, or the statute, and read it — mostly in the Harvard Law School Caselaw Access Project and on state court and legislature sites. Law-firm articles and legal directories were used only to find cases, never as the source.
• Quotes checked word for word. Each state's quote was copied from the opinion or statute and then checked again against the live page before publishing.
• Fixed labels. Every state gets one of 6 labels with fixed wording. Where a state softens its rule, the card says how in its own line rather than inventing a new label. Some states are labelled differently by different summaries — Pennsylvania, Maryland and Nebraska among them — and their cards explain the choice.
• Confidence. High where the opinion or statute states the rule and we found nothing later changing it; medium where the leading case is old or we relied on a later case summarising it; low where sources conflict.
• What it doesn't cover. Streams and other watercourses, groundwater, flooding from public storm sewers, farm drainage districts and state stormwater permits follow different rules. Damages, deadlines and defenses vary by state.
• Not legal advice. This is general information to help you know what to ask. Laws and cases change; the date on each card is when it was last checked. For a real dispute, talk to a licensed attorney in your state.

Open data: neighbor runoff law by state (CSV)

The full table is free to download: neighbor-water-runoff-laws-by-state.csv (one row per state: doctrine and label, modifier, rule summary, leading authority with year and URL, other authorities, quote and its URL, confidence, verification date and source URLs). It is licensed CC BY 4.0: use it for anything with credit to Yard Drainage Fixes and a link to this page.

To cite this page: Yard Drainage Fixes, “Neighbor Water Runoff Laws by State,” checked October 17, 2026, https://www.yarddrainagefixes.com/learning-center/neighbor-water-runoff-laws-by-state