Business, industry and planning guidance

Risk assessment

Assessing risk is the first step in managing it, meaning you need to know your risks before addressing them. For this, you can assess your own risk or request the services of a suitable consultant to help you. The following publications may assist:

Risk factors

In assessing erosion and sediment risks, consider the factors that are specific to your site and activities that you are undertaking.

Site risk factors

The characteristics of a site and its surrounds all contribute to site risk, as summarised in Table 1.

Table 1: Site risk factors

Site factor Description Considerations
Soil types

Different soil types have varying:

  • levels of resistance to erosion
  • potential for dust generation in dry conditions
  • potential for sediment-laden runoff generation in wet conditions.

Soil types can include sand, silt, clay, silty clay, rock, sodic soils, and others.

Dispersive or sodic soils (soils with high sodium content) tend to:

  • have lower soil cohesion (ability for soil particles to stick together) which reduces soil structure
  • readily break up and disperse (prone to water and wind erosion)
  • remain suspended in water (cause turbidity)
  • have reduced drainage ability.

Silty soil, sands and gravels are prone to wind erosion and dust emissions.

Permeable soils tend to soak up more water and produce less runoff.

Surface cover Surface cover, including vegetation onsite.
  • Maintaining dense vegetation cover over the soil surface helps to stabilise soil structure and makes it resistant to erosion forces like rain, flowing water, and wind.
  • Maintain deep rooted plants to hold slopes together.
Topography Changes in land level on a site (slopes/gradients).  Gravity increases water flow rates on sloped areas of land which makes them prone to water erosion.
Onsite activities and nearby sensitive areas
  • Where an activity occurs onsite (e.g. soil disturbance or stockpiling) can impact on nearby sensitive areas such as waterways and drainage systems.
  • Additionally, other sensitive areas need protection from flowing water (e.g. slope embankments).

Identification of onsite and nearby sensitive areas combined with good planning, location, and management of onsite activities, can reduce the risk of: 

  • soil disturbance
  • erosion
  • sediment deposits into aquatic systems (which affects plants and animals and increases flood potential)
  • drainage. 
Drainage and runoff
  • Onsite or nearby drainage systems.
  • Flow of water onto and around a site.
  • Water may flow onto a site (as runoff) from an adjacent site or may begin on a site.
  • This may carry or collect sediment which can discharge into and clog drainage lines or waterways. 
Weather and timing 
  • The prevailing weather conditions can be a result of the site location or the season.
  • The longer that a site area is exposed to wind or rain is an important factor in determining the erosion potential. 
  • The erosion potential varies according to the time of year and prevailing wind and rain conditions. Seasonal conditions need to be considered when planning timing of activities.
  • Site activities should be managed to minimise soil exposure times (staging or phasing activities can help, rather than clearing an entire area at once).
  • How much water or wind will you need to control?
  • This is relevant to the control measures that you need to consider and how useful they are under load.

Activity risk factors

The following table provides guidance on activities and potential risks and controls. However, the controls outlined are suggested only and may not always be appropriate. Other measures that create equal or better outcomes may need to be tailored to the individual circumstances of your site and activity in order to meet your obligations.

Table 2: Activity risk factors and potential controls

Activity  Examples of risk  Relevant erosion controls (Table 3)  Relevant sediment controls (Table 4) 

Exposing soil

  • Land clearing and development.
  • Excavations. 

Soil that is exposed to water and wind erosion can cause:  

  • dust emissions
  • movement and loss of top soil
  • transport of soil contaminants
  • deposits of dust or sediment into waterways
  • formation of soil surface rills and gullies
  • excavation wall collapse. 







Material stockpiling

  • Construction material storage.
  • Earth material extraction.
  • Earth material supply, handling and transfer. 

Material stockpiles can be subject to wind or water erosion resulting in:  

  • movement of material, nutrients, contaminants
  • dust emissions.
  • Manage offsite flows.
  • Prevent erosion of bulk materials.
  • Slow wind or water flow rates down.




Water extraction and disposal 

  • Dewatering.
  • Block/paver cutting slurry. 
  • Water flowing down steep pit excavations can cause wall collapse.
  • Discharge of sediment or slurries to drainage systems.

Manage offsite flows.

  • Perimeter structures.
  • Water treatment, filtration or retention. 

Infrastructure development and protection 

  • Road.
  • Rail.
  • Bridges.
  • Embankments.
  • Dams.
  • Utility connections.

Unprotected or unmaintained assets may be subject to:  

  • wind erosion and dust emissions
  • embankment or batter slope collapse
  • dam wall failure
  • undermined structural footings.
  • Soil conservation.
  • Prevent erosion of bulk materials.
  • Manage offsite flows.
  • Soil stabilisation.


Unsealed roads and thoroughfares

  • Engineering.
  • Vehicle movements on unsealed roads.

Unsealed roads or thoroughfares which are unprotected, unmaintained, or overused may be subject to:  

  • increased churn by vehicle tyres
  • increased emission of sediment laden flows
  • increased emission of dust. 
  • Prevent wind erosion on unsealed roads.
  • Minimise erosion potential from unsealed roads or thoroughfares.
  • Perimeter structures.
  • Protect the existing drainage system. 


Development of:   

  • swales
  • wetlands
  • slopes
  • walls
  • mounds. 

Landscaping can result in:  

  • erosion of disturbed and exposed soils
  • erosion prone slopes and mounds
  • emission of dust
  • emission of sediment into wetlands
  • wetlands overtopping and causing erosion of nearby areas.
  • Manage offsite flows.
  • Soil stabilisation.
  • Prevent erosion of bulk materials.
  • Perimeter structures to capture and manage sediment.
  • Water treatment, filtration, or retention. 

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Page last updated on 1 Mar 2019