The Impact of Cyclone Jasper on Wet Tropics Waterways
One year on from Cyclone Jasper, we reflect on the devastation it caused
and the lessons learned to build a resilient future
On December 13, 2023, Tropical Cyclone Jasper made landfall near Wujal Wujal, just north of Port Douglas, as a Category 2 system. Though its winds reached speeds of up to 220 km/h, it was the unprecedented rainfall and flooding that left a lasting mark.
The slow-moving cyclone unleashed over two meters of rain in less than a week in some areas, potentially making it the wettest cyclone in Australia’s history.
In the aftermath, rivers swelled to record-breaking levels. The Barron River’s floodwaters surpassed a 41-year-old record, while the Daintree River broke its 2019 record by over two meters.The floods devastated the Wet Tropics, damaging agriculture, infrastructure, small businesses, and tourism. Early insurance claims for damages to properties alone totaled $357 million, while the full cost of environmental damage remains incalculable.
In the aftermath, rivers swelled to record-breaking levels. The Barron River’s floodwaters surpassed a 41-year-old record, while the Daintree River broke its 2019 record by over two meters.The floods devastated the Wet Tropics, damaging agriculture, infrastructure, small businesses, and tourism. Early insurance claims for damages to properties alone totaled $357 million, while the full cost of environmental damage remains incalculable.
Beyond the immediate human and economic toll, Cyclone Jasper had major environmental consequences, particularly for waterways.
One of the most widespread environmental impacts on waterways was the severe erosion around waterways. Riverbank erosion is caused by the flow of water in floods and is particularly pronounced in areas with limited riparian vegetation, especially on the outside bend of a waterway where flow velocities are higher. The floods caused enormous amounts of erosion across the Wet Tropics, undermining river banks, causing sedimentation of waterways and inshore marine environments, and leaving large areas vulnerable to further erosion in subsequent floods.
Beyond the immediate human and economic toll, Cyclone Jasper had major environmental consequences, particularly for waterways.
One of the most widespread environmental impacts on waterways was the severe erosion around waterways. Riverbank erosion is caused by the flow of water in floods and is particularly pronounced in areas with limited riparian vegetation, especially on the outside bend of a waterway where flow velocities are higher. The floods caused enormous amounts of erosion across the Wet Tropics, undermining river banks, causing sedimentation of waterways and inshore marine environments, and leaving large areas vulnerable to further erosion in subsequent floods.
The record-breaking rainfall associated with Cyclone Jasper triggered major landslides across the north of the region, particularly on steep hill sides. Although many of these areas were covered in thick rainforest, the soil became saturated, increasing its weight and decreasing its cohesion, causing landslides.
The tonnes of sediment displaced from the hillsides then washed into the waterways, causing sedimentation and impacting water quality in freshwater and marine environments.
The amount of sediment washed into our waterways as a result of the erosion and landslides across the region is difficult to quantify, however there were some serious impacts on freshwater and inshore marine habitats, particularly for water quality, corals and seagrass.
For example, Emmagen Creek just north of Cape Tribulation, which is home to a high diversity of unique freshwater fish species has been severely impacted by the landslides in the catchment (before and after slideshow shown). Sediment from the landslides has washed into the creek causing sedimentation and a loss of habitat for many species and may take years to clear from the system.
Floods can promote the spread of invasive plants and animals such as amazon frogbit and tilapia.
Flooding can connect isolated water bodies, allowing invasive species to move into new areas.
Invasive species often thrive in disturbed environments, allowing them to spread and establish after an event such as this.
Floods can promote the spread of invasive plants and animals such as amazon frogbit and tilapia.
Flooding can connect isolated water bodies, allowing invasive species to move into new areas.
Invasive species often thrive in disturbed environments, allowing them to spread and establish after an event such as this.
Waterways are dynamic features in the landscape, changing course over time. However, large floods such as this can accelerate the process, changing the path of rivers and the way water moves across the landscape. Rapid changes such as this can threaten infrastructure, agriculture and residential areas.
Coral bleaching is normally associated with warm ocean temperatures however it can also be caused by sediment-laden freshwater plumes which can induce a similar stress response from corals.
Significant flood events produce large flood plumes that carry freshwater and sediment to inshore reefs, which can cause bleaching as was seen at some inshore reefs around Snapper Island near the Daintree River after Cyclone Jasper.
Coral bleaching is normally associated with warm ocean temperatures however it can also be caused by sediment-laden freshwater plumes which can induce a similar stress response from corals.
Significant flood events produce large flood plumes that carry freshwater and sediment to inshore reefs, which can cause bleaching as was seen at some inshore reefs around Snapper Island near the Daintree River after Cyclone Jasper.
The heavy rains that followed Cyclone Jasper were a stark reminder of a changing climate’s potential impacts. Extreme rainfall and floods are becoming more frequent as the average global temperature rises.
Climate scientist Dr Steve Turton says that for every temperature increase of one degree centigrade the atmosphere can hold an extra seven per cent of water vapour, and when the conditions are right it is released as intense rainfall.
“Last year was the warmest year on record and sea surface temperatures were record-breaking every single day. Then along comes Cyclone Jasper and instead of moving away and taking the rain with it, the system remained stationary, bringing down moist air down and causing several days of torrential rain,” he says.
The heavy rains that followed Cyclone Jasper were a stark reminder of a changing climate’s potential impacts. Extreme rainfall and floods are becoming more frequent as the average global temperature rises.
Climate scientist Dr Steve Turton says that for every temperature increase of one degree centigrade the atmosphere can hold an extra seven per cent of water vapour, and when the conditions are right it is released as intense rainfall.
“Last year was the warmest year on record and sea surface temperatures were record-breaking every single day. Then along comes Cyclone Jasper and instead of moving away and taking the rain with it, the system remained stationary, bringing down moist air down and causing several days of torrential rain,” he says.
Recovery from the impacts of Cyclone Jasper will take many years. Landholders, local, state and federal government, river improvement trusts and natural resource management groups are working to repair some areas of the landscape that have been impacted but the scale of the damage is likely to be much larger than the resources available.
The Cyclone Jasper floods have highlighted the importance of a resilient landscape. Resilience is a word that gets used a lot but what does it actually mean in this context? A resilient landscape is one that is robust to change and able to resist and bounce back from disturbance.
For example, a river bordered by dense, healthy riparian vegetation is significantly more capable of resisting erosion and regenerating after a flood than one with little to no vegetation. This resilience not only helps protect the ecosystem but also mitigates future damage, making it an essential focus for recovery efforts.
Recovery from the impacts of Cyclone Jasper will take many years. Landholders, local, state and federal government, river improvement trusts and natural resource management groups are working to repair some areas of the landscape that have been impacted but the scale of the damage is likely to be much larger than the resources available.
The Cyclone Jasper floods have highlighted the importance of a resilient landscape. Resilience is a word that gets used a lot but what does it actually mean in this context? A resilient landscape is one that is robust to change and able to resist and bounce back from disturbance.
For example, a river bordered by dense, healthy riparian vegetation is significantly more capable of resisting erosion and regenerating after a flood than one with little to no vegetation. This resilience not only helps protect the ecosystem but also mitigates future damage, making it an essential focus for recovery efforts.
Floods and cyclones are natural events that have shaped our environment and waterways over millennia. These events are important for connecting aquatic habitats, replenishing flood plains and wetlands, recharging groundwater supplies, dispersing and germinating seeds and helping cycle nutrients and sediments.
However, models predict that they will likely grow in intensity, and we can expect similar events and similar impacts into the future as our climate changes. The good news is that we can learn from these events and invest in the resilience of our waterways and landscapes.
Floods and cyclones are natural events that have shaped our environment and waterways over millennia. These events are important for connecting aquatic habitats, replenishing flood plains and wetlands, recharging groundwater supplies, dispersing and germinating seeds and helping cycle nutrients and sediments.
However, models predict that they will likely grow in intensity, and we can expect similar events and similar impacts into the future as our climate changes. The good news is that we can learn from these events and invest in the resilience of our waterways and landscapes.
Have you seen any significant environmental impacts across the Wet Tropics?
Let us know!
Wet Tropics Waterways and Terrain NRM have teamed up to build a register that helps the community report areas that are in need of environmental restoration. Whether that is erosion control, wetland restoration, fish barrier removal, invasive weed removal or pest animal control, you can report it through the Waterway Restoration Register.
