It is increasingly apparent that high resolution terrain mapping is required to better understand and target erosion . The BBB region has been fortunate in acquiring several Light Detection and Ranging ( LIDAR ) tiles ( 100- 300km 2 ). These datasets allow the construction of high-resolution Digital Elevation Models ( DEM ) ( 1 m 2 ), that are suitable for terrain mapping at fine scales .
The catchment modelling team , consulted with the P2R science group , who had begun work on the mapping of erosion features with LIDAR . Through initial collaboration a GIS tool was designed that semi autonomously mapped gully edges and derived volumes . However , it became obvious that the work could provide many additional products for catchment science and modelling .
Through further work , The P2R gully monitoring team designed and constructed the Digital Incision Reconstruction Tool ( DIRT ) ( e . g . Figure 7 ). This tool produces a suite of outputs including , but not limited to the following ,
• Polygon delineations of incision ( gully and stream ) edges ,
• Modelled incision caps with raster layer incision depth relative to the modelled cap ,
• Average thalweg slope per mapped incision ,
• Headcut knickpoints and their respective contributing catchments ( contributing catchments , include relevant attributes , including , slope , soiltype , roughness , vegetation cover etc ),
• Classification of incision ( Hillslope / Alluvial / Colluvial )
• Incision connectivity to main channel ( ie , continuous or discontinuous )
• Infrastructure module which , maps roads dams and contour banks , etc
• Finally a DEM of Difference ( DOD ), allowing rates of erosion and deposition to be determined by feature type
This is an emerging area of reef catchment science , and it is envisaged that , more on ground monitoring will be required to value add to the spatial datasets . We predict that the frequency and spatial footprint of LIDAR will increase over time , likely driving a drop in cost per km 2 . Thus LIDAR has the potential to be a key component of reef market infrastructure .
Figure 7 . High resolution LIDAR showing erosional DIRT mapped features .
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