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Understanding Flood Risk in Sorell

Like most of Tasmania’s East Coast, the Sorell Municipality, on average, receives a lower than average annual rainfall when compared with the rest of the State.  However, the Municipality on occasions, is subject to rainfall events that are high in intensity and short in duration.  These events can occur at any time during the year.  Depending on the amount of rain and where it falls determines the extent of local flooding issues.  Flash floods are a result of fast rising water and fast receding water. Flood events are often shallow waters, but fast moving.

Flooding also occurs when the Municipality has received regular rainfall over an extended period of time and the ground becomes so saturated that it cannot absorb any further rainfall.   In coastal areas when a high tide occurs in the same period as an extreme rainfall event, flooding can be even worse.

Most residents are aware of the rivers, streams and rivulets that run through the region.  There are also a number of constructed drains (e.g. the one that runs along Montagu Street) and naturally occurring overland drainage pathways that generally remain dry for most of the year.  It is important that all these overland drainage paths are well maintained and kept free from obstructions including fencing and other structures.

Your property maybe at risk of flood damage if:

  • You are near a waterway, including naturally occurring ephemeral waterways that are usually dry.
  • Your property is in a natural depression, including behind a coastal dune strip.
  • Your property slopes up into surrounding farmland or natural bushland.
  • Your property is in a low-lying area near the coast or a waterway.
  • Your property is located at the bottom of a hill with adjoining developed properties above.

Flood maps are available for the urban areas to see if your property maybe subject to flooding.

Flood Maps

Council commissioned a number of flood studies for the Municipality, including:

  • Urban areas of Sorell, Midway Point and the Southern Beaches 1% AEP flood mapping: broad scale flood modelling used to approximate flood extents through the Municipality’s overland flow paths at a whole of catchment scale.

They show the drainage lines and natural flood ways where flood water is predicted to travel through during a 1% AEP event.

The modelling has been done at a catchment wide level and provides an indication of potential hazards but may not be accurate at a property level. Seek independent advice for your site-specific flood risk.

The modelling identifies major flow paths during extreme events. It does not pick up localised nuisance flooding associated with undersized pits or pipes or localised road camber. It also does not pick up un-concentrated sheet flow, such as what occurs at the bush-urban interface. Just because your property is not within the mapped hazard extent does not mean you won’t be affected in a flood.

Sorell Council Flood Modelling 1 in 100 Year Event

Council’s Role in Mitigating Flood Risk

Before a flood:

  • Model and map flood risk.
  • Statutory planning in flood risk areas.
  • Undertake stormwater pit and grate inspections prior to a major rainfall event.

During a flood:

  • Keep the pipe system clear of blockages.
  • Ensure the main natural drains are kept free of debris as much as possible.
  • Respond to customer requests about blockages with the existing infrastructure.

After a flood:

  • Clear debris from waterways, roadways, and parks.
  • Repair damaged assets.

Whilst Council does all it can within available resources to ensure the drainage/stormwater infrastructure for which Council is responsible is efficiently and effectively maintained and continuously improved, it should be noted that it is not unusual for drainage and storm water infrastructure to reach capacity very quickly during significant rain events.

Property Owner’s Role in Mitigating Flood Risk

We encourage you to monitor local flood levels and seek appropriate weather warnings via the Bureau of Meteorology’s Flood Knowledge Centre – Flood Knowledge Centre (bom.gov.au)

Property owners should do everything practicable to ensure drainage and stormwater infrastructure within their properties is kept clear of debris.

It is important for property owners in flood prone areas to have an emergency/flood plan in place to prepare for such an event, including ensuring the safety of animals and stock where practicable.

Before a flood:

  • Know and understand the likely flood risk at your property.
  • Ensure that you have adequate insurance, including coverage for all parts of your property likely to be affected (such as fences and outbuildings).
  • Prepare a flood response plan.

During a flood:

  • Move valuable and hazardous possessions to higher levels.
  • Follow your flood response plan.
  • If evacuating, do not return home until you have been advised it is safe to do so.
  • Call the SES on 132 500 if you are in immediate danger.

After a flood:

  • Contact your insurance company if there has been damage to your property.
  • Check in with your neighbours.

To learn more about what you can do before, during and after floods, please visit the Tasmania State Emergency Service website.

Next topic: Flood Mapping