Stormwater, tides and surcharge in the Redlands

Updated October 2026

There is a particular Redlands problem that looks like a blocked drain and is not one. The pipe is clear, the grates are clean, and the water still will not go away. That is surcharge, and on low-lying bayside land it has more to do with grade and tide than with anything stuck in a pipe. Redlands Blocked Drains connects you with QBCC-licensed local drain plumbers who diagnose stormwater and surcharge problems across the Redlands.

What surcharge actually is

A drainage system moves water downhill to a discharge point. If the discharge point is under water, nothing moves. If the grade is almost flat, water moves slowly even when the outlet is clear. Put a heavy summer storm over a flat system at high tide and the water backs up from the bottom, out of pits, out of gullies and across the ground.

That is why the same house can flood in one storm and sail through a heavier one. The variable is not the rain, it is where the tide was when the rain arrived.

Why the Redlands gets it

Flat grades. The mainland is a low bayside strip. Old stormwater runs have very little fall, and nothing can be done about fall without re-laying pipe.
Tidal influence. The foreshore streets at Thorneside, Wellington Point, Cleveland, Victoria Point, Redland Bay, Coochiemudlo Island, Amity Point and Point Lookout all drain towards water that rises twice a day.
Subtropical rainfall. Summer storms arrive in volume over a short period, which is the worst case for a flat system.
Age. A great deal of the bayside stormwater network was laid for a smaller catchment with less hard surface above it than exists now.
Hard surfacing since. Every patio, shed, driveway and extension added over the decades sends more water to the same pipe.

The council maps this. The Redland City Plan runs a flood and storm tide hazard overlay and a coastal protection erosion prone areas overlay, and the council's overlay maps are the authority on any particular property. This page does not tell you whether your land is mapped, and you should be sceptical of anyone who tells you that without opening the map.

The overflow relief gully is doing its job

On the sewer side, the thing that saves the house during a surcharge event is the overflow relief gully, the grated drain outside set lower than the lowest fixture indoors. When the system backs up, the water lifts that grate and spills outside rather than coming up through the shower.

Which means the worst thing you can do in a surcharge event is block it. People do, because it is spilling waste water in the yard and that is unpleasant, and then the next lowest opening becomes the floor waste in the bathroom. Keep it clear, keep it liftable, keep people and pets away from anything that has surfaced. The full gully guide is on this site.

What can actually be done

Some of this is cheap and some of it is not, and an honest plumber will tell you which category your property is in.

Rule out a real blockage first. Silt in a flat run is extremely common and it is not surcharge. A camera and a jet blast settle it, and the footage shows whether the pipe is holding water because of grade or because of sediment.
Silt pits. Catch sediment somewhere you can empty it rather than letting it settle in the pipe. Cheap, effective, and rarely installed.
Downpipe and surface redirection. Getting roof water away from the slab and into something adequate solves a surprising share of pooling complaints.
Re-grading or re-laying a run. The real fix for back-fall, and it is construction work with excavation, so the acid sulfate soil and vegetation questions below apply.
Non-return devices on stormwater outlets. On a tidal outlet, a flap or non-return valve can stop tidal water coming back up the line. Whether it suits your system is a site-specific judgement and needs the right product properly installed.
Pumped systems. On a genuinely low site below the tidal outlet level, the only reliable answer is a sump and pump. That is a real project with running costs and a maintenance obligation, and it should be the answer after the cheaper ones have been ruled out, not before.

The two things that come before any digging

Acid sulfate soils. The Redland City Plan maps potential acid sulfate soils across the coastal and estuarine lowland, with a performance outcome requiring that development minimise and manage disturbance so that acid and metal contaminants are not released. Deep excavation and dewatering below the natural surface can trigger those management requirements. This page states no trigger depth or level, because the thresholds come from the state planning policy and the council's mapping and are site-specific. The contractor confirms what applies before quoting.

Vegetation. Most of the mainland sits inside the state's koala mapping, and the council runs an environmental significance overlay and a local law protecting vegetation on private property. Trenching a new drainage line through an established tree's root zone is a permit question. It is also usually avoidable, and a good contractor will route around it.

And in all cases, use Before You Dig Australia before anything goes in the ground.

Foreshore and canal properties

Raby Bay in Cleveland and Aquatic Paradise in Birkdale sit at the sharp end of this. Canal frontage means the outlet level is tidal by definition, salt air and salt water shorten the life of grates, risers and metal fittings, and property values make a water event expensive. Work close to the water can also attract extra assessment under the coastal protection overlay. None of that is a reason to do nothing. It is a reason to get the diagnosis right before spending money.

Frequently asked questions

My drain only floods on a king tide. Is it blocked?

Probably not, but rule it out with a camera before spending on anything bigger. If the pipe is clear, you are dealing with surcharge and the answers are different.

Can the council fix it?

The council's network is the council's, and a blocked council pit or kerb inlet should be reported. Drainage on your own property is yours. Where the problem is the catchment rather than any one pipe, it is a council planning matter rather than a plumbing job, and the overlay maps are where that conversation starts.

Is a non-return valve a good idea?

On a tidal outlet it can be, and on the wrong system it creates a new problem by holding water in. It depends on levels, on the outlet and on what else drains through that line, so it is a site assessment rather than a product recommendation.

Will a bigger pipe fix it?

If the restriction is the pipe, yes. If the restriction is the tide or the fall, a bigger pipe fills up slightly more slowly and then does the same thing.

Does this affect sewer or just stormwater?

Both, in different ways. Stormwater surcharges because it cannot discharge. The sewer system is affected by groundwater and stormwater getting into it through cracked joints and illegal connections, which is one more reason old clay line and heavy rain do not mix well.