Overland flow paths in Auckland: what they are and what you can and cannot do
Since the 2023 floods, overland flow paths have moved from an engineering footnote to something that decides what can be built, where fences can go, and which sites need a serious stormwater design. Auckland Council now runs an assessment programme across the region.
If you own land, are developing a site, or are trying to work out why the council has written to you about stormwater, this is the concept underneath it.
What an overland flow path actually is
Council defines them as routes where water naturally flows across the ground. They carry extra stormwater during heavy rain and when the pipe network is full, blocked, or does not exist at all. When that happens, these paths become temporary, fast-flowing streams.
The critical detail for property owners is the next one: overland flow paths cross both public and private land. Having one run through your section is common, and it is not in itself a problem. Obstructing it is.
An overland flow path is not a fault in your property. It is the route the water was always going to take. The damage happens when something is put in the way of it.
How to find out whether one crosses your property
Council publishes a Flood Viewer for exactly this purpose. It shows whether an overland flow path is mapped across a given property. For anyone buying land, developing a site, or planning a fence or a shed, that check takes minutes and is the cheapest piece of due diligence available.
What blocks a flow path
Council is specific about this. Water builds up and enters homes when a flow path is blocked by items such as fences, buildings, trees or stored items. The everyday version of the problem is rarely dramatic:
Solid fences installed across the path with no gap at ground level
Sheds, bins, outdoor furniture and general storage placed in the route
Landscaping, raised beds and retaining that redirect or dam the flow
Debris, rubbish and garden waste that wash downstream and block something else
Blocked gutters, downpipes and catchpits that push more water into the path than it was carrying
Buildings placed across the route
The council assessment programme
Council assesses overland flow paths across Auckland to understand how rainwater moves across properties in heavy rain, to plan and prioritise wider improvements, and to identify stormwater issues that raise flood risk for a home and the surrounding area.
If a property sits in an overland flow path area, the owner may receive a letter explaining why an assessment is needed. The visit is short, in the order of fifteen to thirty minutes, and looks at how stormwater flows across the site during heavy rainfall and whether improvements are needed. Any required action is followed up by letter or email. Where a flow path continues to cause serious problems, council may take action to ensure it is kept clear.
What you can do about it
Council guidance for owners is practical rather than punitive:
Keep the route clear of debris, rubbish, garden waste and anything that can be carried downstream
Do not place furniture, bins, sheds or storage in a flow path
Keep gutters, downpipes and catchpits clear and working
Design fences and landscaping so water can pass, using raised or slatted designs rather than solid panels to ground
Use permeable surfaces for driveways and outdoor areas where possible
Get professional advice and the right consents before making major changes
Council also publishes downloadable guides on maintaining gutters, downpipes and catchpits, on ground soakage, and specifically on fences that block overland flow paths.
What it means if you are developing
On a development site an overland flow path is a design input, not an obstacle to be removed. It affects building platform position, levels, fencing, driveway design and the stormwater system, and it interacts with whatever detention or soakage the site requires. Getting it wrong is expensive twice: once at consent, and again when the water arrives.
Related reading: stormwater detention tanks and soakage and on-site stormwater disposal.
Questions we get asked
How do I know if I have an overland flow path?
Check the council Flood Viewer, which maps overland flow paths across Auckland by property.
Can I build over an overland flow path?
Blocking a flow path with a building is exactly what council is trying to prevent, because it pushes water into homes. Major changes need professional advice and the right consents before you start.
Can I fence across one?
Only in a way that lets water pass. Council specifically recommends raised or slatted designs rather than solid fences to ground level, and publishes a guide on fences that block flow paths.
What happens in a council assessment?
A visit of roughly fifteen to thirty minutes to check how stormwater flows across the property in heavy rain and whether improvements are needed. Any actions follow by letter or email.
Does having one affect what I can build?
It is a design input on any development site, affecting platform position, levels, fencing, driveway design and the stormwater system. It is better handled at design stage than at consent stage.
This page summarises publicly available Auckland Council information at the time of writing and is general in nature. Confirm requirements for your property with Auckland Council.
Draeinail Construction has been putting drainage in the ground across Auckland and the Franklin district since 2006. Request a quote or call Darryn Muir on 021 271 0035.
