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Water outside a Liverpool home, a guide by Dotto

Liverpool, on the Georges River

When water reaches a Liverpool home from outside

When the water comes from outside, this is the guide: the river in flood, stormwater off the roof and street, sewage that overflows, and the tank and hot water unit in the yard. This guide is written and published by Dotto, from the official sources linked on every page.

A drawn flood gauge post standing in a river, with three flood classes marked beside it: minor, moderate and major. 321 MajorModerateMinor
Drawing, not to scale. The Bureau of Meteorology warns of three classes of flooding: minor, moderate and major.

The river

Liverpool sits on a floodplain

Two major rivers run through Liverpool City Council’s area, the Georges and the Nepean, fed by many smaller creeks, and the council says many parts of its area are subject to flooding.

The Georges River has a catchment of 960 square kilometres and a population of about one million people, and the river itself is about 100 kilometres long. Its tributaries include Cabramatta Creek and Prospect Creek. Council has prepared flood studies and floodplain risk management studies and plans for all the major waterways in its area. Local councils hold primary responsibility for flood planning, with Sydney Water taking part where its stormwater assets are.

To see how flooding has behaved in a particular place, NSW SES publishes Local Flood Insights: maps of flood-prone areas, historic flood events and modelled flood risk.

Reading the gauge

The Bureau of Meteorology’s latest river heights include a gauge called Georges River at Liverpool. Most river heights are given in Local Gauge Height, which typically reads zero near the lowest level the water reaches in dry conditions.

The three classes of flooding

Where it has specialised warning systems, the Bureau warns of minor, moderate or major flooding. In its own words, shortened:

Minor
Causes inconvenience. Low-lying areas beside watercourses go under, minor roads may close and low-level bridges may be submerged. In towns and suburbs, some backyards and buildings below floor level may be affected.
Moderate
All of that, over a larger area. Main traffic routes may be affected, some buildings may be affected above floor level, and evacuation may be required.
Major
All of that, with extensive urban or rural areas under water. Many buildings may be affected above floor level, properties and towns are likely to be isolated, and evacuation may be required. Utility services may be impacted.

The three warning levels

NSW SES issues flood warnings under the Australian Warning System, at three levels.

  • AdviceThe threat has risen to a heightened level. Keep up to date as things change.
  • Watch and ActThings are changing, and it is time to start acting now to protect yourself and your family. Do not enter floodwater.
  • Emergency WarningThe top level. You may be in danger, and you need to act immediately.

When flash flooding is likely, NSW SES says the best thing to do is leave low-lying homes and businesses early, well ahead of the water, but only if it is safe to do so.

Two pipes

Rain and sewage take different pipes

Rain that runs off roofs, roads and paths is stormwater. It often flows from property drains to street gutters run by the local council, then on through channels, pipes and creeks. Unlike wastewater, it is not treated before it reaches creeks, rivers and the ocean.

Wastewater is the used water from sinks, showers and toilets, and it travels through Sydney Water’s pipes to be treated. Sydney Water’s policy keeps the two apart in both directions: no wastewater into a stormwater pipe, and no stormwater or roof water into the wastewater system. In very heavy rain, water that gets into wastewater pipes through cracks, faulty joints and direct stormwater connections can push them past their capacity, and they overflow.

Read mark 5: stormwater and sewer are different

A wide grey river in steady rain, mangroves on both banks and a long concrete bridge with a steam train crossing it.
Rain on a wide river: a heritage steam train on the Como Bridge, as the photographer describes it. This is not Liverpool. Photo by Peaky_82 on Unsplash

After the water goes down

Going back to the house

Once people have evacuated, it is NSW SES that says when a flood-affected area is safe to return to. Do not go back to your property while the emergency is still active.

If the power, gas or water supply has been damaged or disconnected, NSW SES says not to try to reconnect it yourself. Every electrical connection and appliance affected by water should be inspected by a licensed electrician before it is used again, and gas appliances and gas bottles that have been in floodwater should be inspected for safety before use.

Food and drink that has been in contact with floodwater, water included, should be thrown out. Floodwater and the debris it leaves may be contaminated with sewage.

Read mark 6: plumbing after a flood, step by step

Numbers from NSW SES

In a life-threatening emergency, call Triple Zero 000

For emergency help in a flood, storm or tsunami, NSW SES 132 500

The guide

Six marks on the post

Each mark answers one question about water outside a Liverpool home, from the official pages it links to.

  1. Plumbing after a floodGoing back in, in the order NSW SES and NSW Health set out.
  2. Stormwater and sewer are differentTwo pipes, two destinations, and the rule that keeps them apart.
  3. Blocked drains: what to check firstWhat blocks a drain, how to stay safe, and who clears it.
  4. Rainwater tanksPlacing, connecting and keeping a tank, and what a flood does to one.
  5. Hot water systems explainedThe six kinds, where each one lives, and how big.
  6. New home plumbing and warrantiesSix years, two years, and the records to keep.