Heavy rain can cause real problems for Brisbane backyards, especially when water starts to flow across property surfaces. Overland flow and stormwater flooding often lead to soggy lawns and damage to gardens. Water entering your home can also cause structural damage if not managed the right way.
Slick N Co was called in by a homeowner in The Gap to fix her flooded backyard. For the last 20 years Pam’s pergola and the backyard were unusable when it rained. The rain caused persistent flooding and water pooling across the entire surface.
Weo fixed the drainage issues and Pam can now enjoy her pergola all year round.
Key Takeaways
- Overland flow flooding is a common problem for Brisbane properties
- Effective drainage and landscaping solutions help prevent stormwater damage
Flood Impact on Brisbane Backyards
Overland flow and stormwater flooding impacts thousands of Brisbane homes. Common effects include soil erosion, loss of garden plants, and damage to outdoor structures. Strong flows can knock down fences or wash away garden beds.
Pools of water attract mosquitoes and cause slippery or muddy conditions. Water run-off can also enter garages or sheds, damaging stored items and tools. The impact is especially severe if backyards sit in natural overland flow paths or lack defences like retaining walls and gardens.
Over time, water damage can change the shape of the yard, affect tree roots, and increase maintenance and insurance costs.
The Gap Site Investigation
For Pam’s property we completed a detailed site investigation. This work included pot holing to confirm exact depths of the plumbing services. We then used CCTV camera inspections of the existing stormwater drain.
Our team identified several critical issues:
Broken Stormwater
The stormwater drainage around the perimeter of the pergola had been incorrectly installed. The pergola installer hadn’t glued the pipes together. This allowed tree roots to enter the pipe. During rain events the back fall in the pipework and cracks in the pipes caused the surrounding ground to flood.
Undersized Downpipe
The 80m² roof area above the pergola was serviced by a single undersized 50mm downpipe. This pipe was not able to handle water during heavy rainfall, leading to overflow of the gutters. The overflow caused more flooding of the ground around the pergola.
Missing ground drainage system
A retaining wall sat next to the pergola. However, there was no sign of a French drain, drainage rock, or other waterproofing methods to manage subsoil water pressure, and prevent water ingress into the pergola area.
The water escaping from the cracked pipe and the overflowing gutter had nowhere to go. This caused waterlogging, damage to nearby brick work, and mould build up.
Scope of Works
To fix these issues, Slick N Co carried out a full drainage rectification and stormwater upgrade in this area.
These works included:
Manual Excavation
Due to limited access to the backyard, all excavation behind the retaining wall was completed by hand. We dug an 18m trench at 0.5m deep so that it sat below the existing slab level. This depth allowed excess water to flow away from the home.
Drainage Installation
A new aggie pipe drain system was then installed behind the retaining wall. Over the pipe we placed washed drainage rock. The rock was wrapped in geofabric sheeting to prevent sediment contamination and promote long-term effectiveness. The wall and trench was also lined with core fluting.
Roof Drainage Upgrades
Two additional 90mm downpipes were installed to replace the single undersized 50mm pipe. The new downpipes significantly improving the roof’s capacity to shed water during peak rain events.
New Stormwater Mains
New 100mm stormwater lines were laid and correctly connected to the existing household system. The rainwater is now captured and flows away from the home to the stormwater mains in the street.
Ground reinstatement
Upon completion of all plumbing works, the area was carefully reinstated. This work including the spreading of new topsoil and laying of matching blue couch turf to restore the rear yard to its original condition.
The Gap Project Outcome
The rectification works have successfully resolved the flooding issues that previously rendered the rear pergola unusable during rain. Pam now has a functional and dry outdoor area that can be used year-round with the peace of mind that her stormwater system is up to standard.
Customer Testimonial
Slick N Co solved all of my long standing stormwater issues. They were thoroughly professional, kept me fully informed and left the property looking extremely neat and tidy. It was an absolute pleasure to deal with them.
Pam – The Gap, Brisbane
How to Flood Proof Your Home
Homes in Brisbane face a risk of overland flow and stormwater flooding, especially during heavy rain. Strengthening a home’s flood resilience requires careful planning and abiding by current building standards.
Proven flood-prevention strategies include using landscaped slopes to redirect water flow away from living areas, installing new drains, or retrofitting your home’s drainage system. The right combination can prevent water from pooling and protect your property.
Slick N Co offers draining solutions for existing homes, civil earthworks for infill and new subdivisions, and commercial plumbing solutions for local businesses.
Frequently Asked Questions
Brisbane backyards face unique challenges with stormwater and overland flow, often due to heavy rainfall and changes in the landscape.
What Is Overland Flow?
Overland flow and stormwater floods are common issues for many Brisbane homes. Overland flow is rainwater that moves across the ground after heavy storms, rather than soaking into the soil or going into drains.
When the ground cannot absorb more water, it travels along the surface. In Brisbane, this is a serious issue due to the region’s weather and many steep blocks and valleys.
The path water takes during overland flow is called an overland flow path. These paths often follow natural dips, slopes, or low spots in a backyard. Overland flow is different from river flooding, as it comes from local rainfall and stormwater run-off, not the Brisbane River.
What are the common causes of stormwater flooding?
Stormwater flooding happens when drains, gutters, and creeks cannot handle the water from severe storms.
In Brisbane, common causes include:
- Sudden, heavy rainfall from severe or flash storms
- Blocked or under-sized stormwater drains
- Poorly maintained gutters, downpipes, or yard drainage systems
- Hard surfaces like driveways and patios that increase water runoff
When rain falls faster than the land or drains can cope, stormwater collects and floods low areas or backyards. Stormwater run-off can also pick up soil, rubbish, and debris, making erosion worse and increasing the risk of local flooding.
What homes are most likely to flood in Brisbane?
Homes located next near the Brisbane River, near creeks, or in low-lying areas are at higher risk of overland flow or riverine based flooding. Storm surges caused by tropical cyclones, or high tides combined with major storms can also cause localised flooding.
The Brisbane City Council’s Flood Awareness Map can help you identify if your property is affected.
The suburbs most at risk of flooding include:
| Albion Ashgrove Bardon Brighton Carina Coopers Plains Hemmant Lota | Morningside Nudgee Beach Windsor Rocklea Sandgate Tingalpa Indooroopilly Wynnum West |
How can I direct overland flow on my property?
Shape the land to direct water away from the house and towards drains or the street. Install swales, small channels, or underground pipes to guide water flow during storms. Use permeable surfaces in gardens, such as gravel or porous pavers, to slow down water and reduce pooling.
Slick N Co are experts in experts in earthmoving and sub surface plumbing. We can reshape your backyard when we fix or replace existing drains, sewers, or stormwater systems.
What does stormwater management cover?
Good stormwater management is the first defence against flooding on your property.
Effective solutions can include:
- Well-designed drainage systems, earth swales, and storm water storage tanks to handle excess run-off
- Keeping gutters and drains clear prevents blockages
- Permeable paving and rain gardens to help absorb and slow down rainwater
By directing water away from foundations and living spaces, homeowners can reduce the risk of water entering the home.
Who is responsible for managing stormwater drainage?
The Brisbane City Council manages public drainage systems outside private boundaries. Brisbane property owners manage stormwater drainage within their boundaries.
If you build or alter a home near drainage systems, you will need a certified plumber to do this work and to certify its completed to Queensland and local council rules.
Slick N Co are experienced plumbers located in Brisbane. We are a member of Master Plumbers Queensland. We are also fully licenced by the Queensland Building and Construction Commission (QBCC) and the Queensland Government.
Are flooding issues disclosed when buying a home?
In previous years, Queensland vendors and their agents were not legally obliged to disclose a property’s flood zone status. However, the Queensland Property Law Act 2023 has now changed from a ‘buyer beware’ to a detailed disclosure model.
In addition to improved legal protections, its is wise to ask the Brisbane Council for specific advice about the property, particularly if you want to subdivide the land, renovate, or add an extension to your home. Slick N Co can then help you with all your plumbing and earthworks jobs.
What are pre-purchase plumbing inspections?
Slick N Co offers pre-purchase plumbing inspections so that you have a comprehensive understanding of the home’s water, sewer, and stormwater systems. We also check the home’s hot water system, toilets, taps, gutters, and downpipes.
During inspections we use a CCTV camera to inspect the pipes and drains so that you don’t face nasty surprises after you move in. Older homes and Queenslanders are most at risk as the galvanised water pipes are often corroded, which causes low water pressure and blocking.
Older homes may also share a combined drain with neighbouring properties. These clay pipe drains can become brittle then crack over time, causing waste water and sewerage to leak.
