Riverine, flash flooding and coastal inundation information for communities along the D’Entrecasteaux Channel, including lunawani / Bruny Island

Draft for community input – email ses@ses.tas.gov.au .

Storms often affect the D’Entrecasteaux Channel area, bringing heavy rain and damaging winds. Stormwater runoff and flash flooding can affect many areas during a severe storm. Areas that are prone to flooding from rivers (riverine flooding) are:

• Snug – low lying areas to the South of Snug River downstream of the Channel Hwy, mainly near the Esplanade North, Pybus St & Gillies St
• Adventure Bay – near Captain Cooks Creek

In both cases flooding is more likely with storm surge at high tides.

All waterways in the area are short, and so river gauges cannot provide sufficient warning. Flash flooding can impact:

• Roadways at low-lying river crossings, including the Channel Highway for short periods in some places, the Huon Highway near Sandfly and Sandfly Road
• 6 properties in Margate near Margate Rivulet or North West Bay Rivulet
• Several shacks near the mouth of Captain Cooks Creek at Adventure Bay, Bruny Island.

Some properties may become isolated for short periods due to flooding across roads. Debris can also be washed across roads, blocking access for longer times.

There are some low-lying shoreline areas that are at risk of coastal inundation.  Coastal flooding is more likely during storm events at high tide. Areas at most risk include:

• the Esplanade Dru Point, Margate and Barretta waterfront areas
• Snug foreshore
• Lower Snug/ Old Station Rd, Conningham
• Bruny Island Main Rd near Great Bay and the Isthmus
• Adventure Bay near Captain Cooks Creek
• Dennes Point Nebraska Beach, and some areas of the Bruny Island Main Road near Great Bay and the Isthmus.

Coastal erosion can also impact some areas. This is more likely during storm/ flood events.

See the Tasmanian Strategic Flood Maps to view the flood maps in more detail. To check if your property is at risk of coastal inundation or erosion see alert.tas.gov.au/get-ready/risk-ready/. SES is currently adding riverine flood maps to TasALERT risk-ready.

The maps in this guide show the level of flooding from rivers or coastal inundation that has at least a 1% chance of happening any year (climate up to 2016). You are likely to experience flooding such as that shown in the maps in your lifetime. Tasmanians need to prepare for flood events that may not happen often as well as the minor flooding they may have experienced. Even if your home is not flooded, you should be prepared for isolation plus potential power and telecommunications outages. Depending on where the rain falls and how heavy it is, other access roads may also be impassable. Travel in the area is likely to be difficult or impossible until roads are clear.  If you are safe at home or elsewhere, it is usually best you stay where you are until the flooding subsides, unless there is an emergency. If you need to evacuate, you should leave early, before flood waters rise.

Go to tasalert.com or listen to ABC local radio 936AM for warnings and advice.

Are you at risk of flood?

Aside from Snug river mouth and Adventure Bay near Captain Cook’s Creek, riverine flooding is not a concern for most areas around the Channel, but there is a long history of severe storms bringing heavy rain.  Severe storms causing storm water run-off and flooding issues happened for example 1872, 1881, 1954, 1954, 1960, 1973, 1983, 1995, 1996, 2004, 205, 2010, 2011, 2015 and 2018.

What should I do?

• Check the map to see whether your home or business could flood.
• Assess your home or business and prepare it to minimise possible flood damage.
• Check if you can safely get to your home, work, or school during a flood.
• Prepare a Home Emergency Plan. See Get Ready for Emergencies – A guide for individuals and households to prepare for emergencies. 
• If you may be isolated and you must have access to services, you may need to evacuate early. Think about what you might need to take.

Floods like the one shown in the map will occur again. No two floods are the same.

If you live in a low-lying area or near a watercourse, your house may flood. Even if your home is safe, you may need to detour around flooded areas or your road access may be cut. Unless there are landslips, trees down or debris over roads, most areas are likely to only be isolated for a few hours.

Never drive into or enter flood waters. Roads and bridges may be washed out or unsafe. Avoid travel during floods.

Knowing what to do can save your life and help protect your property. Having a Home Emergency Plan is one of the best ways to prepare. See Get Ready for Emergencies – A guide for individuals and households to prepare for emergencies. Decide on weather and rainfall triggers for when to act.

Bureau of Meteorology Forecasts, Warnings, and Observations

The Bureau issues a Flood Warning, Severe Weather Warning and/or Thunderstorm Warning for heavy rainfall that may lead to flash flooding whenever heavy rain is expected in an area. The time between the warning and heavy rain occurring can vary from an hour to 24 hours or more.

There are no river level flood warnings for any rivers in the area – the short catchment means river gauge information would not provide enough warning time.

Check Rainfall Observations at Mt Wellington / kunanyi, Margate, Dennes Point and other nearby rain gauges. Given the very short warning times, it is best to act on the predictive BoM warnings rather than wait for any flood alerts during rainfall.

The Mt Koonya Radar is useful to be aware in real-time where heavy rainfall is falling.  Radar Rainfall estimates can also fill in gaps in areas where there are no rainfall stations.

Understand the warnings and key information

Keep aware of what is happening around you. Check forecasts, observations and warnings regularly.

• TasALERT.com
• your local ABC radio station or
• the Bureau of Meteorology’s website.

	Advice (Yellow): an incident has started. There is no immediate danger. Stay up to date in case the situation changes.
	Watch and Act (Orange): There is a heightened level of threat. Conditions are changing and you need to start taking action now to protect you and your family
	Emergency Warning (Red): An Emergency Warning is the highest level of warning. You may be in danger and need to take action immediately. Any delay now puts your life at risk.
	Community update (Blue): Specific information and updates for affected communities regarding a particular event or incident.
	Incident (White): an incident is the initial occurrence of an event before it becomes an emergency warning. As soon as an incident is reported, TasALERT published basic information including the type and location of incident.

For more information see www.ses.tas.gov.au/warnings/ .

Flood levels

While no two floods are the same, the following describes what you can expect at different flood levels around the area. Even if your property is not flooded, you need to think about access. Different levels of rainfall can cause flooding depending on its intensity, duration and how wet the ground is beforehand and where the rain falls. Flooding is more likely at high tides around coastal areas. Weather systems producing heavy rain can also cause storm surge, coastal inundation and coastal erosion.

Minor flooding

Minor flooding can affect

• Some minor road river crossings
• Agricultural land on river flats
• Riverside parklands. Coastal parkland areas might also be affected at high tide.
• This level of flooding has about a 10% or more chance of happening any year.

Moderate flooding

A moderate flooding event can inundate riverside parklands and low-lying backyards and streets. Some homes and other buildings may start to be affected, particularly

• Brookfield near Margate and a couple of properties along Margate Rivulet
• Low-lying areas near Snug River mouth
• Some other low-lying areas near the coast and waterways

This level of flooding has about a 2-5% chance of happening any year.

Storm water, water and sewerage systems may be impacted.

Major flooding

Major flooding with a 1% chance of happening could impact:

• Many properties around the mouth of the Snug River
• Some properties near Captain Cooks Creek, Adventure Bay, Bruny Island
• Some properties along North West Bay Rivulet and Margate Rivulet
• May mean some areas of Channel Highway and Bruny Island Main Road may be cut for a short time. Some areas may be isolated.
• At high tide there may be some extra areas also at risk of coastal inundation, such as:
• Margate Dru Point/ Esplanade and Barretta
• Snug foreshore, including areas around the Oval to the caravan park
• Lower Snug/ Conningham near Snug Creek and Old Station Road
• Kettering Marina/ Ferry Road area
• Woodbridge foreshore
• On Bruny Island, Dennes Point, various areas along Nebraska Beach
• Adventure Bay especially around Captain Cooks Rivulet
• Some sections of Bruny Island Main Road near Great Bay, the Isthmus and Alonnah.

Know your risk, get ready, reduce risk where you can, connect with others, stay alert and act safe.

Before a flood

1. Know your risk

Flooding often happens in Tasmania and can cause widespread and significant damage. In the past 200 years there have been 78 flood related deaths in Tasmania. This guide is to help you understand flood risk in your area.

2. Prepare your household

Have an emergency plan that covers storms and floods

Thinking about what you would do in a storm or flood means you are more prepared and everyone is safer. Have an emergency plan that everyone in your household understands. There are checklists to help you think through your plan – see Get Ready for Emergencies – A guide for individuals and households to prepare for emergencies. 
Check your plan regularly and test it by everyone in the household thinking through a flooding scenario that may affect your household.

Prepare an Emergency Kit

Regularly test batteries in radios and torches.

3. Reduce your risk from flooding where you can

• Think about storms, flooding and other hazards when buying, maintaining or developing property.
• Trim or remove trees and branches overhanging your home, business or near powerlines on your property.
• Keep your gutters and drains clear.

4. Connect with others

Know your neighbours and get involved in your community.  A connected community is a safer and more resilient community in an emergency and can help everyone recover better afterwards. Check that family and neighbours are safe and aware of what’s happening.

During

5. Keep up to date

Keep aware of what is happening around you. Check forecasts, observations and warnings regularly. 

• TasALERT 
• your local ABC radio station or
• the Bureau of Meteorology’s website.

6. Act Safe

• Supervise children.
• Prepare for possible power, water or internet outages.
• Check your emergency kit is ready to go.
• Keep clear of flooded areas such as drains. NEVER walk, play, ride or drive in floodwater. You can’t always see what is under the water or how deep or fast-moving the water is. It is easy to be swept away and drown in as little as 20cm of fast-moving water. Flood water can be dangerous.

When your home may be flooded

• Put household items up high to minimise possible damage.
• Turn off the electricity and gas if it is safe to do so. 
• A great way to stop sewerage flowing back into your home is to place sandbags inside plastic bags and use them to block toilets and cover drains and sinks.
• Leave while you can get out safely.

If you need to evacuate

• Follow the advice from SES / Tasmania Police.  
• Take your emergency kit. 
• Go to friends or family in a safer place or an evacuation centre. 
• Let others know where you have gone.

Look after your animals

You are responsible for your animals in an emergency. If you have pets and other animals it will take you longer to evacuate in a flood or other emergency. Move livestock from flood prone areas well before flood waters may rise.  For more information see

• RSPCA’s guidance on preparing for animals in an emergency
• Huon Valley Council’s advice on preparing an emergency pet plan
• the Primary producer farm flood readiness toolkit.

Avoid travelling during storms and after storms

• Do not go sightseeing. Sightseers delay emergency services and cause accidents.
• Watch out for hazards such as
  • water over roads
  • damaged powerlines
  • landslides
  • damaged roads
  • falling trees or roofing iron.
• Never drive through flood waters. Most deaths and rescues in floods are from people driving through flood waters.
• Drive slowly and turn your headlights on roads not affected by flood waters.

After

• Keep listening for ABC Local Radio updates, road re-openings, community meetings, etc.
• If you left your home, do not return home until SES or Tasmania Police tell you it is safe to do so.
• Be aware of road hazards, such as mud or debris on the road, damaged roads/bridges and crews working on clean-up and repairs.

If your home has been damaged

• Stay at ground level while checking for damage. Be careful of fallen trees, broken glass, loose roofing or other hazards.
• Wear strong boots, gloves and protective clothes. 
• Use a torch, never use matches or candles inside flood affected buildings. 
• Boil all drinking water until you are told the tap water is safe again.
• Do not turn on it is tested by a licensed electrician or gas fitter for safety.
• If your home is damaged and you need to stay somewhere else, take your emergency kit and pets with you
• Take photos of any damage if safe for you to do so and contact your insurance company.
• Supervise children.
• Check neighbours are okay.

For further information go to www.ses.tas.gov.au

Staying informed and further information

Current warnings (TasAlerts) alerts.tas.gov.au

Bureau of Meteorology (BoM)

Emergency Broadcasters ABC 936AM

TASSES Social Media

• facebook.com/sestasmania

Preparing for Flood Emergencies ses.tas.gov.au/plan-prepare/flood 

Derwent Valley Council  derwentvalley.tas.gov.au   6261 8500

National Relay Service (NRS) relayservice.gov.au

Disclaimer

The maps show potential flooding risks from consistent levels of rainfall across catchments, such as a 1% Annual Exceedance Probability (AEP).  In flooding events, rainfall is likely to be more inconsistent across a catchment, so these flood maps should be considered indicative only.  The mapped areas of flood risk show higher probability of inundation. Other areas have lower probability of flooding, but in severe and rare events (rarer than 1%AEP), other lower areas may be also at risk of inundation.

The information in this guide is current at the date of publication. While every effort has been taken to ensure the validity and accuracy of the data presented, the State Emergency Service does not take responsibility for data error or omission. Please see the standard Tasmanian Government’s Copyright and Disclaimer Statement for more details.