A Khandallah owner once brought me photos of her back lawn under ten centimetres of water every time it rained hard, taken over three winters, timestamped, with a rough sketch of where the water was coming from. That file was one of the easier ones I dealt with, not because the fix was simple, but because she had done the one thing most people skip: she documented it properly before asking anyone for help. Her neighbour uphill had regraded a section of garden two years earlier, and the water that used to spread across open ground now ran in a defined channel straight onto her lawn.
The general principle behind surface water
The starting point in most district plans and in general law is that a landowner should not deliberately concentrate or divert natural surface water flow in a way that causes damage to a neighbouring property. Water that already drained downhill across open, undeveloped ground is treated differently from water that has been artificially collected, piped, or channelled and then discharged onto a lower section. Quality Planning’s guidance on stormwater and surface water under the RMA sets out how this general principle is usually applied across different district plans. Reshaping a garden, adding hard paving, or building a wall can change how water behaves even without any intention to cause harm, and the person who changed the ground is generally the one expected to manage the consequence, not the neighbour who receives it.
Why documentation matters more than the first phone call
Before raising the issue with a neighbour or the council, the useful record is dated photos taken during and after a rain event, a rough measurement of how much water collects and where, and ideally a note of when the change on the upper section happened relative to when the flooding started. Verbal complaints are easy to dispute later; a paper or photo record with dates on it is not. A short, factual written note to the neighbour — what has been observed, when, and what would help — is generally a better first move than a heated conversation at the fence, partly because it creates the same kind of record if the issue does not resolve quickly.
When it is the council’s business and when it is not
If the runoff involves a public stormwater system — an overloaded council pipe, a blocked public sump, water backing up from infrastructure the council owns — that is squarely council business and worth reporting to them directly. If the issue is one section’s private regrading or paving sending water onto another private section, with no public infrastructure involved, that generally sits as a private matter between the two owners, potentially resolved through direct negotiation, mediation, or in a persistent case, a civil claim, rather than something the council can compel a neighbour to fix. District plans sometimes carry rules about maximum impermeable coverage or stormwater management for larger works, which the council can enforce if a resource consent condition was breached, but a garden reshaped without any consent trigger at all often falls outside anything the council can directly act on.
Engineering fixes and where their limits sit
A swale — a shallow, vegetated channel that slows and spreads water rather than concentrating it — is often the first thing suggested for diffuse surface flow, and it can work well within a single section without needing any consent. A cut-off drain along a boundary, intercepting water before it reaches the lower property, is a step up in engineering and sometimes needs to tie into a piped system, which brings drainage connection rules into play — what you may and may not connect into that system is covered separately in drainage connections: what you may and may not connect. Any solution that discharges water directly onto a neighbour’s land, rather than to a lawful outlet such as a public stormwater main or an approved soakage area, generally is not a fix at all — it just moves the same problem to a different boundary, and a council or a court is unlikely to see it as resolved.
Frequently asked questions
Is a neighbour responsible for water that naturally flowed downhill anyway? Generally no — the distinction most plans and courts draw is between natural flow and water that has been concentrated, piped, or diverted by human alteration of the land.
What should I do first if a neighbour’s regrading is flooding my section? Record it properly first — dated photos, a rough measurement, and a written note to the neighbour — before escalating to the council or legal advice.
Can the council make my neighbour fix a private drainage problem? Only if public infrastructure or a specific consent condition is involved; a private regrading dispute with no such trigger is usually a civil matter between the two owners.