Managing forestry after flooding and prolonged rainfall

How flooding and prolonged wet weather can affect forests

Native forests on floodplains adapt to flooding as a natural part of the Australian landscape. You should still take care to assess and manage your forest under the Private Native Forestry Codes of Practice (PNF Codes) after flooding or prolonged rainfall.

There are three key aspects of your private native forest to consider during and after flooding and prolonged wet weather:

• weed control
• soil erosion
• forest infrastructure.

Forest management after flood or prolonged rainfall

Following a flood or prolonged rainfall, do not start repair works or operations using machinery until soils are no longer saturated. Saturated soils are prone to erosion and will not compact sufficiently.

It may be possible to implement erosion control works without machinery. For example, you can install hay bales, silt fencing and/or coir logs to capture sediment.

You may use:

• forwarders
• excavators
• truck-mounted loaders

as stationary loaders when there is runoff from the log landing. All other machinery on the log landing must remain stationary when there is runoff from the log landing surface, unless the log landing is made of gravel or other stable material.

Assess condition of forest infrastructure

Once it is appropriate and safe to do so, assess any damage to:

• roads
• access tracks
• drainage features and
• drainage feature crossings.

When undertaking repairs, refer to the PNF Codes. This will help ensure construction of the forest infrastructure meets required standards.

Drainage lines and crossings may have become blocked with debris during higher flows. It is important to remove significant blockages. This will help to maintain the integrity of crossings and allow fish passage through drainage lines.

After a flood, debris may have washed into fencing and against tree trunks requiring repair or removal of fence lines. If you need to remove native vegetation to undertake fencing repairs in your PNF area, talk to Local Land Services for advice on allowable activities within PNF Plan areas.

If you have undertaken recent harvest operations, assess snig track drainage and erosion control structures for damage. Consider any actions needed to repair or remediate drainage and erosion control structures.

Under the PNF Codes, snigging, use of log landings and portable mill operations must not occur when:

• there is runoff from the snig track surface
• the soils have become saturated
• machinery ruts the soil more than 200mm deep below the track surface over a section 20m or longer.

Prioritise weed control

During flood events, weeds can end up in flood waters. The weeds are then carried downstream to areas where they were not previously established. As soon as it is safe and allowable to do so under the PNF Codes, assess your forest for weed outbreaks. Early weed treatment will prevent bigger outbreaks and will be more cost effective long-term.

PNF Codes after floods or prolonged rainfall

There are parts of the Private Native Forestry Codes that you should treat with extra care after floods or prolonged rainfall.

Section 4: Protection of the environment

Areas of existing mass movement and dispersible erodible soils are likely to be more prone to erosion during and after heavy rainfall. Erosion controls are important in areas with these landscape features after a flood or significant rainfall event.

Drainage feature protections apply to all PNF Plan areas. Riparian exclusion and buffer zones are particularly important during and after a flood to reduce soil erosion.

Reassess drainage features and unmapped drainage lines within your PNF Plan area. These may have changed during flooding or prolonged rainfall. Apply drainage feature protections in the PNF Codes as required.

Section 5: Construction and maintenance of forest infrastructure

Following a flood or prolonged rainfall, there may be damage to roads and drainage feature crossings. Maintain existing roads to minimise the construction of new roads and drainage feature crossings as far as practicable within PNF Plan areas.

Runoff flows may have removed or flattened vegetation around drainage discharge areas. This can create a higher risk of erosion. If stable discharge areas are difficult to find, use other sediment control structures. You can use sediment fencing, hay bales or rock armour to stabilise the area and reduce erosion and sediment movement into waterways.

Take caution when re-commencing operations. Track surfaces may look dry, the subsoil may still be saturated. This makes heavy vehicle movements unsafe and may lead to high repair costs if the road surface fails.

Landholders must document all works in their forest operation plan under the PNF Codes.

Removing a tree or other living native vegetation that may be presenting a safety risk

The allowable activities in PNF Plans allow for removal of trees to reduce an imminent risk of serious personal injury or damage to property. Such clearing should be only be undertaken to the minimum extent necessary.

If you are unsure how to apply the allowable activities and PNF Codes to your situation, please contact LLS for assistance.

Prepare your forest for future flood and prolonged rainfall events

Investing in forest management ahead of floods and prolonged rainfall can reduce the impact they may have on your forest and forest infrastructure. Road upgrades can reduce roads susceptibility to wash away and erosion. Hard stand areas on log dumps, such as gravel beds can allow trucks to park and turn around with less risk of soil displacement.