Flood

Riverine flooding

Riverine flooding happens when there’s been a lot of rain over several days or weeks. When there is too much water, creeks and rivers can burst their banks and that’s when flooding happens.

Flash flooding

Flash flooding happens where there is a lot of rain in a short period of time. It can happen anywhere, at any time, and often without a lot of warning. Flash flooding is dangerous. Expect to see powerful, water moving fast. In built up, urban areas drains and creeks can fill up quickly and spread to nearby buildings, streets, roads and parks. Certain areas within the City of Launceston are prone to flash flooding due to older storm water and sewerage infrastructure and the topography of the land.

Minor flooding

If the water level reaches the minor flood level, it causes inconvenience. Low-lying areas next to water sources are inundated. Minor roads may be closed and low-level bridges submerged. In urban areas flooding may affect some backyards and buildings below floor level as well as bicycle and pedestrian paths. In rural areas removal of livestock and equipment may be required.

Moderate flooding

If the water level reaches the moderate flood level, the area of flood inundation is larger. Main traffic routes may be affected. Some buildings may be affected above floor level. Evacuation may be required. In rural areas removal of livestock is necessary.

Major flooding

If the water level reaches the major flood level large areas are inundated. Many buildings may be affected above floor level. Properties and towns may be isolated and major traffic routes closed. Evacuation may be required. Utility services may be affected.

To understand floods further visit the Bureau of Meteorology's Flood Knowledge Centre.

Depending on your location, you may experience floods differently. Your location can help determine whether you are likely to experience flooding. Understanding the type of flooding you are likely to experience will help you to prepare for how quickly the flooding is likely to occur, the duration of heightened flood water levels, where flooding is likely to occur, and the impact it will have on your home, workplace and transport networks.

Note that your home does not need to be at risk of flood for you to be impacted. Isolation is an issue that can impact people living in elevated areas when surrounded by water sources. It can prevent you from coming and going from your home or workplace during a flood. This occurs when major roads are cut-off due to flood waters, meaning that people are unable to leave their homes until the floods have subsided. 

The Launceston Flood Maps provides information on your properties likelihood risk of flooding. The base flood layer is automatically set to show the extent of a 1% AEP* flood however this can be changed by choosing different layers.

Annual Exceedance Probability (AEP) is a term used to the express the percentage of likelihood of a flood of a given size or larger occurring in a given year. If a flood has an AEP of 1%, it has a one in 100 likelihood of occurring in any given year.

Check the Launceston Flood Maps to assess your level of riverine flood risk.

Check the Urban (Stormwater) Flooding Map for flash flooding storm water flood maps. 

*AEP - Annual Exceedance Probability

Everyone must take particular care when they are in the vicinity of the storm water system as storm water drains, manholes, pits and grates pose a danger in both wet and dry weather.

The storm water system criss-crosses the city taking rainwater away from our streets and homes, sending it to the ocean. The system is more than 438 kilometres long, which is approximately the distance from Launceston to Hobart and back. 

Some sections of the storm water drains are only a few metres long, but others run for kilometres. They consist of pipes that narrow down and expand back out.  They have debris traps and deep pits with no ladders - and no means of escape.

When it is not raining, they are homes to rats, snakes and spiders. When it rains, the pipes flow to full capacity, sucking in anything they can from bicycles to wheelie bins.  The storm water system is dangerous in the dry and can be deadly in the wet.

Fast moving storm water

Flowing storm water and hidden debris can easily knock a person over and sweep them away, possibly into storm water drains. It also has the potential to sweep cars of flooded causeways and roads. Never drive through flood water. Turn around and find a safer route.

For more information, view the Water Wise: Floodscapes clip prepared by Tasmanian Visual Artist Karen Revie, Invermay Primary School and Big Picture School. 

Roads are usually flooded before properties. It is important that you stay informed of local road conditions to prevent you and your family becoming isolated. Many drivers rescued from flood waters report that they were in a hurry to get home safely, using this as an excuse to drive through floodwaters. Regardless of the type of car you drive, driving through flood water is extremely dangerous.

Please remember:

• Most flood-related deaths occur at night and involve cars driving on flooded roads. Creeks and rivers can rise very quickly, and the road surface can wash away making water much deeper than it appears.
• Once cars are swept downstream, they will often roll to one side and perhaps flip over entirely leaving the driver and occupants little time to escape.

Launceston was settled at the junction of two rivers - the North Esk and South Esk. These are fed by a system of rivers and lakes that cover 14% of Tasmania. These two rivers meet to form the Tamar/Kanamaluka River.

Most of Invermay and some parts of Newstead sit within the flood plain, an area that will flood in a natural river system. In fact, Invermay's ground level is actually below the high tide, and if the flood levees were not in existence some parts of Invermay would be subject to water inundation twice a day with high tide. 

Since Launceston was established, there have been 36 significant floods with 1929 reputedly the worst. However the years 1852, 1863 and 1893 are also recorded as very serious flood events. The 1929 flood saw the evacuation of 4,000 people. 1,000 homes were inundated and 20 ultimately condemned. During the flood, 4,250 cumecs* of water flowed from the South Esk River and 567 cumecs* flowed from the North Esk River, prompting authorities to seriously consider the need for a new levee system.

Image: Corner of Holbrook and Forster St, Invermay April 1929

A Flood Levee Project to protect areas of Launceston began in the 1960s to provide a level of protection from flood waters.  A series of levees - some as high as four metres - were built as part of the Flood Levee Project to protect the low-lying areas on the flood plain, separating the city from the rivers.  These levees have now been repaired and rebuilt.

Launceston's most recent significant flood was in June 2016, when 2,375 cumecs of water from the South Esk River and approximately 800 cumecs from the North Esk River resulted in the largest flood since 1969. The levees held, limiting damage; however, some unprotected homes and businesses near the Tamar Yacht Basin, Newstead, St Leonards and Nunamara were inundated and Invermay was threatened. Traffic was disrupted due to parts of the city being cut off. The City of Launceston utilised this website and its social media channels to communicate regular updates and evacuation notices and keep community members well-informed.

More recently in October 2022, the City of Launceston again suffered from significant flooding with the North Esk river at a similar height to the 2016 flood, however the South Esk river was significantly lower.

The City of Launceston also has a long history of flash flooding due to urban development in flood prone areas. However significant investment in a variety of projects has improved the infrastructure to minimise the impacts of urban flooding. This work continues to be implemented.

*Cumecs: a cubic metre per second, as a unit of rate of flow of water or refers to the volume of water in the river - one cumec equals one cubic metre of water flowing past a point in one second. One cubic metre of water equals one thousand litres and weighs one tonne.

The City of Launceston has 12km of concrete and earth flood levees which provide increased protection to approximately 6,000 people.

What is a levee?

A levee is a man-made structure built to contain, control or divert the flow of water in order to provide protection to towns and/or agricultural land from flooding. Levees are designed to hold back a certain amount of floodwater.

Levees can be made out of earth or concrete. The crest is the top and the design height is the height of the floodwater the levee is intended to hold back. The freeboard is added to the levee to ensure it can withstand a flood that has reached the levee's design height; it takes into account factors such as wind or wave action of the water, erosion or settling of the earth over time. Freeboard should not be relied upon to hold back water.

Why does a levee fail?

Depending on a levee's age and its condition, water can seep through the levee leading to flooding in the area it has been built to protect. This can happen slowly or suddenly. Fast moving water, trees and animal holes can all lead to a weakness in a levee that can cause it to fail.

Outside of emergencies regular levee inspections are undertaken to ensure levee integrity is maintained.

During a flood incident if levee gates are closed, the City of Launceston will undertake regular patrols across the levee system. The aim of flood levee patrols is to maintain a physical presence and regularly inspect Launceston’s system of flood levees by:

• Monitoring flood levels and condition of levees
• Detection of early warning signs of flood levee failure
• Monitoring imminent and actual flood levee failure

Why do levees overtop?

When a flood occurs, floodwater might flow over the crest of the levee - this is called overtopping. When a levee overtops it will cause flooding in the area behind the levee. Overtopping can be slow or fast and can also cause erosion leading to a full breach of the embankment and rapid high-speed flooding behind the levee.

Charles Street Flood Levee Gate 2016

In 2018, the City of Launceston invested in an update of flood modelling for the North Esk and South Esk rivers. This information assists the City of Launceston to further understand the risks associated with floods, as well as understanding what the future impact may be from a climate change perspective. The data in these reports is of a technical nature but provides important information of the future state of floods in the municipality.

• North and South Esk Rivers Flood Modelling and Mapping  Update Levee Breach Assessment
• North and South Esk Rivers Flood Modelling and Mapping Update Volume 1: Technical Report
• North and South Esk Rivers Flood Modelling and Mapping Update Volume 2: Flood Mapping