Flooding from Tropical Cyclone Jasper

Tropical Cyclone Jasper made landfall in Far North Queensland as a Category 2 storm in December 2023. The slow-moving storm system brought record-breaking rainfall to the region, causing widespread flooding that washed sediments across coastal habitats.

The affected region included parts of the Wet Tropics of Queensland and Great Barrier Reef World Heritage areas – home to valuable mangrove forests, intertidal fringing coral reefs, and seagrass meadows. These coastal habitats are vulnerable to the impacts of terrestrial runoff, including sediment-laden floods.

Surveys of the affected region are needed to understand the environmental impacts of the flooding, potential for recovery, and priority areas for restoration before these ecosystems face another disturbance. Initial assessments can then be followed by monitoring to track recovery over time and inform management decisions to support these valuable coastal ecosystems in the future.

Surveys in 2024 with First Nations partners

Our researchers partnered with Jabalbina, Yirrganydji, Gunggandji, Gunggandji-Mandingalbay Yidinji and Mandubarra Rangers to survey coastal habitats from Cooktown to just south of Cairns.

Together, we assessed the impacts of the flooding on mangrove forests, inshore coral reefs, and seagrass meadows and identified potential sites for restoration, using:

• Helicopter surveys to assess intertidal inshore areas across more than 250km of coastline, including mangrove condition and benthic habitat cover.

• Boat surveys to record subtidal benthic habitats – including algae, coral, and seagrass – and mangrove condition in the Daintree River.

• Drone surveys to assess reef top habitats at Struck Island, Unity Reef, and Ganyjira Reef.

• Remote sensing to map mangrove cover and condition using satellite imagery before and after flooding.

Damage, recovery and potential restoration  

The team found significant damage as well as some signs of potential recovery across the habitats they surveyed:

Mangroves:

• Extensive damage to mangrove ecosystems across the region, particularly in the Bloomfield River and Daintree River. Large areas of mangrove trees were flattened and uprooted, with significant shoreline scouring and erosion. There were also other forested areas where the breathing roots of mangrove trees were buried in mud and silt.

• Losses from erosion damage to mangrove cover of around 19 square kilometres, with early signs of patchy regrowth in the 12 months since flooding.

• Delayed, ongoing damage and loss of mangrove trees in areas where trees survived but had roots buried by sediment deposition.

Corals:

• Many intertidal fringing coral reefs remained smothered in mud, blocking the sunlight needed to sustain existing corals and preventing new coral recruits from becoming established.

• Coral presence at Hope Isles, Snapper Island, Low Isles, and Double Island, but with significant losses in coral cover.

Seagrasses:

• Eight seagrass species spanning over 35 square kilometres, and just four species in the north of the region where impacts were most severe.

• Despite the low cover, these seagrasses show signs of potential recovery if conditions remain favourable.

• Assessing the impact on seagrasses was challenging due to limited data being available on seagrasses in the region prior to Tropical Cyclone Jasper, highlighting the need for expanded monitoring programs.

Late in 2025, the team will return to the area to track natural recovery as well as ongoing impacts. These follow-up surveys will also identify sites for small-scale restoration trials, designed to test techniques and locations where restoration efforts may be most effective.

Future monitoring efforts will use satellite mapping, aerial surveys, and field monitoring to continue to assess habitat condition and recovery, and to guide potential restoration and mitigation options.

Project details

This project is part of the Queensland and Australian Government initiative under the National Environmental Science Program and Commonwealth-State Disaster Recovery Funding Arrangements.