Reinstate floodplain connection

Many rivers have been disconnected from their floodplain. In addition to its many other functions, the floodplain is a natural water storage that can reduce the energy of flood water when the river breaks its banks, by increasing the roughness of the surface that the water is in contact with and facilitating infiltration into the floodplain soils. When floodplains are engaged with the river, they can provide significant reductions in the extent and severity of flooding and disturbance, such as erosion at a local and system-scale. Options to increase connection and floodplain storage include removing artificial levees and re-engaging wetlands. Activities to increase floodplain storage may be incorporated in both floodplain and river management strategies, particularly those relating to flooding. While the floodplain may be the focus the benefits are realised throughout the river channel.

Potential benefits from this intervention:

• Increased flood attenuation through storage of floodwaters in floodplain areas (e.g. water storage in soil profile, in wetlands and/or topographic depressions), with decreased transfer of floodwaters through the river system and reduction in erosion.
• Increased channel-floodplain interactions that benefit ecosystem functioning in the channel, including fish spawning in wetlands, biota movement and feeding on floodplain, and movement of organic matter and nutrients from the floodplain, to river carbon inputs.
• Floodplain ecosystem benefits including riparian vegetation watering.
• Social values including amenity and recreation may come from land zonation that enables periodic flooding. However, when the flood is occurring amenity and recreation in those areas is reduced.

Potential negative implications from this intervention:

• Potential conflicts with infrastructure and private land on the floodplain.
• Flood alleviation in lower reaches (through flow storage) may be at the expense of increased flooding on the floodplain.

Intervention considerations:

• Seek appropriate specialist advice and check legal obligations (e.g. permits).
• This approach is only appropriate when the original channel was connected to the floodplain.
• Take a long-term approach to flood management, recognising the variability in flooding in Queensland and the future predictions of flooding regimes.
• As far as practical attempt to recreate natural flood and storage patterns.
• Take a risk management approach to the consideration of social and economic infrastructure through the consideration of current and future land uses.
• Consider multi-use floodplains, by incorporating emergency response contingencies to deal with conflicts during flooding.
• Where possible remove or relocate artificial levees to increase riverside floodplain capacity.
• Where possible reduce wetland sill levels to re-engage floodplains at sub-bankfull levels.

Additional information

Links:

Wetlands and disaster management

Murray-Darling Basin Floodplain Management Strategy

Brisbane’s Floodsmart Future Strategy 2012-2031

Last updated: 23 June 2022