Before any retaining wall is built, a thorough check of property title documents is essential. Water easements, drainage easements, and riparian (watercourse) setback requirements affect a significant proportion of Blue Mountains properties, particularly those in gullies, on slope interfaces, or in areas with stormwater infrastructure running through or adjacent to the lot.
Building a retaining wall over or too close to an easement area can result in BMCC refusal, forced demolition, or disputes with utility authorities. Checking title documents before you commit to a design takes minutes; fixing a non-compliant wall after construction can take months and cost tens of thousands of dollars.
Quick answer (BLUF)
Check your Certificate of Title and deposited plan (DP) for recorded easements before finalising any retaining wall position. Drainage easements typically prohibit all structures within the easement area. Water main easements restrict construction within specified setbacks. Watercourse setbacks under BMCC controls typically require 10-40 metres clearance from the bank. Your Section 10.7 planning certificate and Sydney Water/council records complete the picture.
Types of easements that affect retaining walls
Drainage easements
Drainage easements are strips of land recorded on title over which council or private parties have the right to construct, access and maintain drainage infrastructure. In the Blue Mountains, drainage easements often correspond to existing stormwater pipes, open drainage channels, or drainage swales.
What they restrict: No permanent structures, including retaining walls, can be built over or within a drainage easement area without the consent of the drainage authority (usually BMCC). In practice, council will almost never consent to a retaining wall over a drainage easement if it would prevent future access to the drainage infrastructure beneath.
Drainage easements are clearly marked on your deposited plan (DP), which is part of your Certificate of Title. They show as hatched or shaded areas with a notation like “1.0m wide drainage easement” or “variable width drainage easement.”
Water main easements
Sydney Water Corporation and some council utilities have water main easements over properties they supply. These are registered on title and restrict construction within specified distances (typically 1-3 metres) from the centre line of the water main.
Retaining wall footings that penetrate the water main protection zone require Sydney Water approval. Footing vibration from excavation, soil movement from excavation and loading from the wall structure itself are all concerns for water main integrity.
Drainage to watercourse easements (private)
Some properties share drainage infrastructure with neighbours, particularly in areas where individual lots drain to a shared drainage line that runs to a creek or gully. These private drainage easements are recorded on title and carry similar restrictions to council drainage easements.
Stormwater right-of-way
In some cases, neighbouring properties have registered rights to drain stormwater across your land. A retaining wall that would redirect this stormwater onto a neighbouring property, or that would block an established stormwater flow path, can give rise to a legal dispute regardless of whether a formal easement is registered.
Watercourse setbacks under BMCC controls
Separate from registered title easements, BMCC’s planning controls impose setbacks from natural watercourses. Under BMLEP 2015 and the associated DCP, development within specified distances from a classified watercourse may require:
- A development application (even for work that might otherwise be exempt)
- An assessment of the work’s impact on the watercourse and its riparian vegetation
- Stormwater management provisions that prevent increased runoff to the watercourse
The setback distance varies depending on the order and classification of the watercourse but is typically 10-40 metres from the bank in the Blue Mountains. First-order headwater streams, which are common in the gully systems throughout the Mountains, are classified as watercourses for this purpose even if they appear seasonal or minor.
In the Blue Mountains, gully systems are not just ecologically sensitive, they are often the primary stormwater conveyance pathway. A retaining wall that redirects or concentrates stormwater into a gully watercourse can cause erosion, waterway degradation and downstream flooding.
How to check before you build
Step 1, Certificate of Title: Your Certificate of Title identifies registered easements. The deposited plan (DP) associated with your title shows the location and extent of easements graphically. Obtain these from the NSW Land Registry Services online portal, or ask your solicitor. Where the deposited plan and the wall’s actual position on the ground don’t obviously line up, a registered surveyor can confirm exactly where the legal boundary runs, see our guide on surveyors and retaining wall boundary disputes for when that step is worth taking. If your retaining wall question is about who owns or is responsible for a boundary structure rather than an easement, see our Who Owns the Boundary Wall? guide for the general ownership principles. And if the dispute is over cost-sharing for a wall rather than an easement issue, note that the Dividing Fences Act generally doesn’t apply, see our guide on the Dividing Fences Act versus retaining wall liability for why that legal mechanism is usually the wrong tool for a wall dispute. If a boundary wall replacement is on the cards and you’re working out cost-sharing with a neighbour, see our guide on splitting replacement costs with a neighbour. If you’re also planning a fence on top of a boundary retaining wall, easement and title checks are only part of the picture, see our Fencing on Retaining Walls guide for the combined-height and liability rules that apply as well.
Step 2, Section 10.7 Planning Certificate: This document (formerly s149 Certificate) lists planning overlays, heritage constraints, flood controls and other restrictions on your property. It will identify if your property is within a waterway setback area, flood planning level, or environmental zone.
Step 3, BMCC BMaps: BMCC’s online mapping tool shows stormwater infrastructure, watercourse classifications, flood extents and heritage overlays overlaid on your property. It won’t show all private easements but will show the major infrastructure layers.
Step 4, Sydney Water: For properties connected to Sydney Water infrastructure, contact Sydney Water to identify any water main or sewerage easements affecting your property. Sydney Water has an online mapping tool (Sydney Water Tap In) for this purpose.
Step 5, Council stormwater records: Contact BMCC’s infrastructure team to request stormwater drainage records for your area. They may have drainage plans showing pipes that are not recorded as formal easements on title but that cross or adjoin your property.
FAQs
Can I build a retaining wall over an existing stormwater pipe?
Rarely. If the pipe is within a registered easement, BMCC consent (and Sydney Water consent if relevant) is required, and this will almost never be granted for a wall that would prevent access for maintenance. If the pipe is not within a registered easement (some older pipes are not), you should still notify BMCC before proceeding, building over unregistered council infrastructure creates liability if the pipe fails.
There’s an easement on my property but I’ve never seen any drainage pipe. Can I ignore it?
No. The easement records an existing right regardless of whether the infrastructure is currently visible or in use. The drainage authority can install infrastructure within the easement area at any time, and any structure you’ve built within the easement may need to be removed at your cost.
My neighbour’s stormwater currently drains across my property. Can I build a retaining wall to redirect it?
Only if you don’t have a registered or implied easement granting your neighbour the right to drain across your land. Unilaterally redirecting a long-established drainage path, even if it’s not formally registered, can give rise to a nuisance claim. Get legal advice before redirecting stormwater that affects a neighbour.
What if it’s the other way around, a neighbour’s wall near a drainage line is failing onto my property?
Drainage line proximity is often part of why a wall fails in the first place, uncontrolled stormwater concentrating behind or beside a structure that wasn’t designed for that flow. See our guide on what to do when the neighbour’s wall is failing onto your land for the documentation and escalation steps, alongside the easement checks above.
Does the watercourse setback apply to a seasonal creek that only runs after rain?
Yes. Under NSW planning law, even seasonal or ephemeral watercourses (those that only run after rainfall) are classified as watercourses for planning purposes, and the setback controls apply. The identification of what constitutes a watercourse on your property may require BMCC or an environmental consultant to confirm.