(vegetation management schemes)
What is riparian vegetation management: This involves the select removal of exotic and/or non flood compatible vegetation and the replanting of suitable native species around the stream or river. This management measure can be useful to increase the discharge capacity of the channel, reduce the severity of erosion and culvert blockage and increase the aesthetics of the waterway. The potential negative impacts include increasing the velocity, timing and severity of flooding downstream and short term environmental impacts of riverine habitat destruction and stream bed and bank stability issues. Please note: This is not the complete removal of all vegetation around the stream or river as this can cause major negative environmental and flood behaviour impacts for the catchment.
Riparian vegetation management may improve community access and recreational use. Why? Over grown banks and the natural varying channel sections can be replaced with more uniform geometry and landscaped features. These landscaped features may generally be more aesthetically appealing and provide increased recreational access opportunities however, can cause adverse environmental impacts including bed and bank stability issues particularly in the short term.
Riparian vegetation management on public land may disadvantage individual members of the community. Why? Depending on the nature and extent of vegetation removal prior to reestablishment of native plants, flood events have the increased potential to cause scour and erosion which could significantly alter flood behaviour and undercut peoples properties. Additionally some people may like the natural aesthetics of the current stream or river and feel like a loss of environmental features occurs when landscaping is undertaking.
Riparian vegetation management if undertaken correctly and slightly improve safety to the community during flooding. Why? A well planned vegetation management scheme involving the propagation and planting of native vegetation that is well suited to the local flood conditions, can stabilise the channel banks which can reduce debris loads and unpredictable flow conditions increasing safety to the community. Just removing vegetation on the other hand can cause significant instability in the channel leading to erosion and sedimentation, unpredictable flow conditions, and increases to the velocity, timing and severity of flooding downstream.
Riparian vegetation management generally does not raise community awareness and understanding of the local flood risk. Why? Riparian vegetation management for flood management purposes is usually quickly forgotten or perceived as a beatification measure and not as a flood reminder. However, local communities are often involved in the planning and implementation of vegetation management through the formation of a Bushcare groups and public meetings. This may locally increase awareness of the local flood risk.
Riparian vegetation management can improve native habitat helping local plants and animals if undertaken correctly. Why? This measure generally involves the select removal of exotic and/or non flood compatible vegetation and the replanting of suitable native species around the stream or river. In the long term this can create important habitat for local plants and animals and stabilise the stream or rivers banks. However, if not properly designed or implemented vegetation removal in particular can quicken the flow of water through the stream channel causing negative environmental and ecological impacts including erosion and scour, habitat destruction, unpredictable flow paths and increased urban pollution runoff.
Riparian vegetation management is generally neutral for water quality. Why? Riparian vegetation management in the short term can be negative as it can reduce the ability for the river or stream to regulate its flows, which causes scour and erosion, increases turbidity and reduces the ability for the floodplain to recharge which collectively decreases water quality. However over the long term the planting of suitable local plants can create a buffer for urban pollutants and stabilise the river or stream, improving water quality.
Riparian vegetation management has minor to moderate initial costs to Council. Why? It is a relatively simple process that involves a works crew physically removing and mulching exotic or non flood compatible vegetation, and then replanting with suitable native plants. Costs for riparian vegetation management schemes generally range from $5 to $50 per linear metre of stream. If a local bush care group is involved Council labour costs can be reduced. Sometimes mitigating downstream impacts including, bank stability measures, flood management works, and associated legislative costs can skew riparian vegetation management costs per linear metre significantly.
Riparian vegetation management generally has minor to moderate ongoing costs to council particularly in the short term. Why? Although maintenance generally only involves weeding and replanting of vegetation, post a storm event works may need to be undertaken to fix stream instability issues such as erosion, scour and head cuts and replanting of native vegetation.
Riparian vegetation management may slightly reduce annual average damages to the community during flooding. Why? A well planned vegetation management scheme involving the propagation and planting of native vegetation that is well suited to the local flood conditions, can stabilise the channel banks which can reduce debris loads and unpredictable flow conditions which can reduce annual average flood damages for the community.
Riparian vegetation management has the potential to cause adverse flood impacts to other areas. Why? As mentioned previously riparian vegetation management particularly in the short has the potential to increase water flow through the stream channel. This amplified conveyance can move flood water downstream quicker and with more energy, causing possible damage to downstream assets and cause erosion and scour within the stream. It is vital that careful planning and consultation with the community and various government agencies is undertaken to ensure riparian vegetation management maximises both environmental and flood management goals.