Reducing flood impacts

7/28/2019 Reducing flood impacts

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Reduce F l o o d I m p a c t s

L o c k y e r V a l l e y R e g i o n a l C o u n c i l

L o c k y e r V a l l e y R e g i o n a l C o u n c i l

Damage following the January 2013 Flood at Mt Sylvia.

To reduce the amount of mud entering waterways, we must minimiseriverbank erosion.

In South East Queensland, planting vegetationalong degraded waterways and protecting existingriverbank vegetation are priority actions to reducethe risks of future ood damage.

Keeping soil on the land The 2011 and 2013 oods in Queenslanddemonstrated the destructive power of water causingover $10 billion dollars of damage to productivefarmland, houses, roads and bridges.

We will continue to receive intense rainfall eventswhich are a regular feature of the sub-tropical climatein South East Queensland.

In order to protect our farms, homes and infrastructure,and reduce the destructive energy of ood waters,we must prepare our catchments for rainfall events byestablishing healthy vegetation along our riverbanks.

Response to FloodingIf we fail to respond to the warnings from recent oodevents and neglect to restore oodplains and increasevegetation in the catchments we will:

• continue to lose valuable agricultural land

• disrupt and endanger lives

• increase the cost of repairing or replacinginfrastructure following future oods

• risk the security of our drinking water supply

• increase sediment and nutrients entering ourwaterways

• smother aquatic habitats that support recreationaland commercial sheries as well as endangeredspecies.

Collaboration is required with farmers and landownersto improve catchment resilience to ood eventsthrough revegetation programs in strategic areas.

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The Mooloolah River oodplain was restored by planting native vegetation.

Planting of riverbank areas at Running Creek in the Albert Catchment.

S u n s h i n e C o a s t C o u n c i l

S c e n i c R i m R e g i o n a l C o u n c i l

Riverbank vegetation reducesood impactsSince European settlement, it is estimated that 80%of South East Queensland’s native vegetation hasbeen cleared for agriculture, industry and housing.

During large rainfall events, riverbank vegetationplays an important role in holding the soil in placeand preventing erosion. Vegetation creates a roughsurface, which helps to slow the ow of water, givingit time to soak into the ground. This reduces oodingdownstream and reduces erosion associated withfast owing water. Slower moving water also allowsthe mud to settle on the land before it reaches ourwaterways.

Scientic modelling predicts that planting vegetation

in the upper catchments can reduce the speed of ood water by up to 50% therefore protecting roads,bridges and other infrastructure downstream.

In addition, by planting vegetation along riverbanksand keeping soil on the land, we are protecting fertilefarming lands and keeping valuable top soilon the land to grow crops.

We need to strategically increase native vegetationalong riverbanks and in the oodplain, to provideresistance to the ood water, in the same way treesand hedges have been used by farmers to protectpaddocks and stock from strong wind.

Multiple benets of riverbank vegetationRiverbank vegetation:

• slows the ow of water and reduces the risk of ood damage to farms, homes, roads and otherinfrastructure.

• reduces the risk of riverbank erosion or collapsebecause the roots of vegetation hold the soil inplace.

• lters rainwater and traps mud, pollutants andother debris before it reaches waterways.

• provides habitat for both land-based and aquaticanimals.

• provides shade and moderates water temperaturethrough over-hanging trees.



Three steps for ood mitigationFloodplains are areas of low-lying land next to a waterway which are subject to ooding. Floodplains with wellestablished vegetation help to spread and slow the ow of oodwater and allow water and soil to soak intothe ground.

Follow the three steps below to manage ooding downstream, increase productivity of land and reduce

damage associated with fast moving water.

Step Two Identify oodplains, be aware of local topographyand avoid developing in high risk areas. Steepslopes or areas where the oodplain is narrow willconcentrate water and cause high energy ooding.

Image: Avoid developing areas of the oodplain which are restricted bysurrounding hills, as these are commonly ash ood areas.

Step OneProtect existing riverbank vegetation and plantmore vegetation along degraded riverbanks. Vegetation will slow the ow of water and causeood water to spread across the oodplain,

reducing the destructive energy of oods.Image: Rain water is intercepted and absorbed by well establishedvegetation, reducing the amount of runoff.

Step Three Optimise the resilience for existing or new landuses. The speed of water and its destructiveenergy is linked to the presence of vegetation onthe oodplain and riverbank. When vegetation hasbeen removed, other solutions to slow the ow of water will be required (e.g. retention basins).

Image: Well established vegetation signicantly reduces the speed of water moving across the landscape. D

e p a r t m e n t o f E n v i r o n m e n t a n d H e r i t a g e P r o t e c t i o n

D e p a r t m e n t o f E n v i r o n m e n t a n d H e r i t a g e P r o t e c t i o n

D e p a r t m e n t o f E n v i r o n m e n t a n d H e r i t a g e P r o t e c t i o n

Speed o water fow

Surace roughness

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High

Fast

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Front and back banner: Helidon Hills Murphy’s Creek Landcare Group

Healthy Waterways

PO Box 13086, George St, Brisbane, QLD 4003

Phone: (07) 3177 9100 Fax: (07) 3177 9190

www.healthywaterways.org

SEQ Catchments

PO Box 13204, George St QLD 4003

Ph: (07) 3211 4404 Fax: (07) 3211 4405

www.seqcatchments.com.au

© Healthy Waterways 2013-007

Healthy WaterwaysHealthy Waterways is a not-for-prot, non-government organisation working to protect andimprove waterway health in South East Queensland.

By becoming a member of Healthy Waterways, youwill belong to a network of people who are workingtogether to protect our waterways. Contact us to ndout more.

H e a l t h y W

a t e r w a y s

By managing erosion we can reduce the amount of soil entering localwaterways.

What you can doWe all have a role to play in protecting and improvingwaterway health.

There are a number of things you can do on yourfarm to manage erosion and reduce the amount of soil entering local waterways.

• Plant native vegetation along waterways.

• Ensure adequate vegetation is planted aroundproduction areas.

• Use strategic plant cover crops to maintaingroundcover in production areas.

• Maintain good groundcover in pastures.

• Fence off riverbanks and provide off streamwatering points to limit animal access to localwaterways.

• Cover exposed soil with mulch.

• Cover stockpiled soils to prevent soil beingtransported into waterways by wind or rain.

• Revegetate cleared land as soon as possible.

• Seek property management advice from SEQCatchments or your local council.

SEQ CatchmentsSEQ Catchments is a not-for-prot organisationhelping to protect the natural resources of South EastQueensland.

SEQ Catchments staff work with Landcare,community groups and landholders to ensure thatimprovements at the property level help achievelandscape level targets in the SEQ NRM Plan.

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Reducing flood impacts