Excessive erosion is one of the leading causes of rehabilitation failing to get sign off against completion criteria. Trying to repair erosion can be difficult and expensive – particularly after operations have finished in an area and equipment is no longer available.
It is much easier and cheaper to identify and fix areas of potential erosion during the process of constructing a landform rather than years after you have completed rehabilitation of a site. Remote sensing can be used at all stages of the landform construction and rehabilitation process to identify high risk areas for erosion and guide management decisions to reduce the risk of requiring long-term maintenance and repairs. It can also be used to gather data to demonstrate that completion criteria for landform stability have been achieved.
In the final article in this series the benefits of undertaking remote sensing during the secondary rehabilitation earthworks to post rehabilitation stages of landform construction are summarised along with some of the other benefits of remote sensing.
Completion of Secondary Earthworks
During the process of applying cover materials and topsoil, a remote sensing survey can identify areas at risk of:
- Excessive erosion
- Exposure of underlying materials
- Excessive infiltration into underlying materials
- Inadequate soil depth for vegetation establishment.
After ripping has been completed, a remote sensing survey can identify any areas where:
- Concentration of surface water may occur
- Overtopping of riplines may occur.
Identifying areas that need rectification while machinery is still on site can result in significant savings in the long run.
After the completion of rehabilitation, use of remote sensing for monitoring performance against completion criteria can remove some of the problems commonly associated with traditional field based transect or quadrat based measurement. Traditional monitoring methods are not particularly effective for landform stability measurement as fixed point transects or quadrats can easily miss large areas of erosion. Remote sensing captures data at the landscape scale – which allows the performance of the whole landform to be understood and assessed.
Remote sensing has many other benefits over traditional ground based monitoring including:
- Opportunity for providing timely, quantifiable and repeatable information
- Ability to be used across large and/or inaccessible areas
- Removal of the safety risk associated with people accessing landforms.
At this stage, remote sensing can be utilised to gather data required to get government sign off on completion criteria. It can be used to identify:
- Gully depth
- Gully spacing
- Rate of change in gully depth and spacing
- Rate of material loss due to sheet erosion
- Change in size of sediment fans and impact on the surrounding environment.
The image below shows the location and depth of erosion gullies on a section of a batter. On a landscape scale this data can also be presented in tables or histograms, identifying the percentage of landform falling within different categories, or categorising the percentage of landform in compliance with completion criteria.
This article focuses on the use of remote sensing for monitoring of landform stability measures. However, it is equally as relevant for other aspects of rehabilitation monitoring that are best represented across a whole landform, such a percent foliar cover and plant density.
Astron are experienced with all aspects of data acquisition, processing and interpretation for remote sensing and rehabilitation monitoring. Contact our Geospatial team on 9421 9600 or via our online form to find out how we can assist you in making your rehabilitation monitoring more cost effective and efficient.