Remotely sensed water body inputs to wetland mapping in Queensland
The Queensland Environmental Protection Agency has developed a comprehensive wetlands mapping methodology as part of a project funded under the Queensland Wetlands Programme (a joint initiative of the Australian and Queensland governments).
The mapping methodology uses existing mapping layers (topographic, vegetation, satellite imagery etc.) and combines these in a manner that maximises the usefulness of each layer. All areas of the state will be mapped to a 1:100,000 scale (minimum feature size of 5ha), with areas of the Great Barrier Reef being mapped at 1:50,000 (minimum feature size of 1ha). The majority of catchments leading to the Great Barrier Reef have already been mapped and mapping for the remainder of Queensland should be completed by July 2007.
Supervised classifications of imagery are processed using a decision tree and the Normalised Difference Water Index (NDWI) is incorporated to identify as many open water body features as possible using Landsat Thematic Mapper and Enhanced Thematic Mapper (TM and ETM+) imagery acquired over 16-years. Classified water body features are combined to identify the extent and multi-temporal characteristics of water bodies. The classified data has been processed and tested to provide a 1ha minimum mapping area.
The mapping and an associated information system (WetlandInfo Queensland) will be used to address the loss and degradation of wetlands and subsequent impacts on water quality and biodiversity in Queensland. The mapping methods facilitate the classification and inventory of Queensland wetlands and provide key information about water extent, inundation regimes, water connectivity and distribution, and the status of wetland disturbance. Resultant information will be used to guide wetland assessment and monitoring. Emerging issues include the determination of water types to define the extent of estuaries, the evaluation of aquatic conditions to facilitate targeted management actions, and the rating of flows to provide a reference for mapped inundation regimes.