Wetland Management Tools & Techniques
Macquarie Marshes Digital Terrain Model
Source: ‘Naturally Speaking’ the newsletter from the NSW Department of Natural Resources (DNR). www.naturalresources.nsw.gov.au
Macquarie Marshes trial a success
DNR’s Central West region has successfully conducted a state-of-the-art Digital Terrain Model trial in the Macquarie Marshes that will help improve the health of the iconic wetlands. This trial has meant the department now knows the best strategy for developing accurate models of floodplain flows within the Marshes.
Digital Terrain Model is a three-dimensional representation of the ground surface and the ground surface information had been collected using the latest Airborne Laser Sensing (ALS) technology. Coastal Councils such as Wollongong and Shoalhaven have used ALS technology for flood hazard mapping, but not for ecological purposes.
Wetland and Water Management
DNR’s Central West region has successfully conducted a state-of-the-art Digital Terrain Model trial in the Macquarie Marshes that will help improve the health of the iconic wetlands. Ultimately, information gathered from the full model will be used to develop a tool that will accurately predict where environmental water flows will travel, and for how long, within the Marshes.
NSW Minister for Natural Resources, Ian Macdonald said this would mean that more informed decisions could be made on where to direct environmental water to best reach, and meet the needs of, the wetland environment – so improving the health of the Marshes.
“The direction, depth, extent and duration of environmental water flows in the Macquarie Marshes are complex because it is an extremely active environment,” Mr Macdonald said.
“This trial has meant the department now knows the best strategy for developing accurate models of floodplain flows within the Marshes.”
Digital Terrain Model
DNR’s Paul Wettin, Central West Manager for Water Management based in Orange said a Digital Terrain Model is a three-dimensional representation of the ground surface and the ground surface information had been collected using the latest Airborne Laser Sensing (ALS) technology.
“ALS basically involves an aeroplane that bounces a laser signal off the ground surface,” Paul said.
“It can detect ground surface height differences as small as 15 cm which is particularly important in very flat terrain areas like the Marshes”.
“Data can be gathered quite speedily over a large area while more traditional ground survey techniques of using poles and theodolites would be prohibitively costly as well as extremely time consuming”.
“This technology is at the forefront of improved wetland management techniques and has recently been used by other researchers at Narran Lake in northwest NSW and for wetlands along the River Murray”.
“Estimates of cost and modelling accuracy that came out of the trial, show that covering most of the model area using ALS is better than total reliance on aerial photographs”.
Application of the Model
Patrick Driver, DNR’s Central West Natural Resources Officer and Project Manager based in Forbes said the aim is to make water inundation predictions at the scale of 1000’s to 10,000’s of hectares.
“This is not a simple task and while we want to have an initial flow-inundation model in the next few years, it will take many more years of development to improve its accuracy”.
“It’s a major investment for the future and eventually the flow-inundation model could be linked to ecological responses, such as River Red Gum tree health.”
Tim O’Connor, Central West Natural Resources Information Officer, Dubbo and other regional staff are providing critical support to the trial and the ongoing project.
A 2.5 by 2.5 kilometre area was selected for the trial in consultation with landholders, departmental staff with on-ground knowledge of the Macquarie Marshes and hydrology consultants who have previous modelling experience in the Marshes.
The trial study is currently being assessed and developed with a ‘technical and user group panel’ including representatives from the Department of Environment and Conservation (DEC), DNR, Central West Catchment Management Authority (CW CMA) and technical experts.
Coastal Applications
ALS techniques are currently used by coastal councils such as Shoalhaven and Wollongong for flood hazard mapping. The technology is able to provide data that the Councils use to determine the movement of flood waters following rain events.
Where this technique is used by coastal councils, the data not been used specifically for environmental purposes. However, for Councils with significant floodplain wetlands the data could assist with the location and duration of floodplain inundation, and therefore assist with the management of some coastal floodplain wetlands.
