Repeat gully terrestrial laser scanners data for geomorphic change detection and estimating volumes of erosion and deposition - Upper Burdekin and Bowen catchments 2016 - 2019 (NESP TWQ 2.1.4, CSIRO)

This dataset contains Riegl terrestrial laser scanner scans and their derived 5 cm gridded digital elevation models (DEMs) collected for up to 4 years between 2016 and 2019 for 4 paired Control/Treatment gully sites being monitored as part of NESP Project 2.1.4. Data collection also contains the DEMs of difference used to estimate changes in gully volume.

The data in presented in this metadata are part of a larger collection and are intended to be viewed in the context of the project. For further information on the project, view the parent metadata record: Demonstration and evaluation of gully remediation on downstream water quality and agricultural production in GBR rangelands (NESP TWQ 2.1.4, CSIRO).

Monitoring of these sites is continuing as part of NESP TWQ Project 5.9. Any temporal extensions to this dataset will be linked to from this record.

Methods:

Riegl terrestrial laser scanner (TLS) scans were collected for up to 5 years between 2015 to and 2019 for 4 paired Control/Treatment NESP gully sites. The fifth site, Mount Wickham, is not scanned. Each site was scanned once a year at the end of the wet season (generally April) using a Riegl terrestrial laser scanner. 

The TLS instrument used in this study was the RIEGL VZ400. The TLS was registered using five ground control points at each site. The control points consisted of a 50 cm star picket driven flush into the ground with a concrete collar. Survey bipods with reflectors were then placed over these marks to establish consistent xyz locations between scanners and for repeat surveys. To link RIEGL scans collected on the same day, additional ‘mobile’ reflectors were placed strategically around the sites. Registration was then performed by matching distances between reflector pairs (see Goodwin et al., 2016 for details). The RIEGL has an inbuilt fine-scan option to accurately locate reflector locations and is used to register separate scans into the same coordinate system with errors typically &lt; 1 cm. These datasets are then projected into real world coordinates using the internal GPS and digital compass. The number of scans captured between sites varies due to differing morphological complexity and area to be mapped. Note that TLS scanning has not occurred at Mt Wickham.

The georeferenced point clouds from each scan position are bundled as ZIP files by site and date. Naming conventions are explained in the data dictionary.

The point clouds for each site and year were combined and converted into 5 cm digital elevation models (DEMs) by determining the minimum Z (elevation) value within a 5 cm grid pattern limited to an area covering the gully headcut and immediate downstream vicinity. A 3x3 grid cell median filter was used to remove spurious elevation values. Minimum Z is assumed to represent ground level. These DEMs are provided in TIFF format for each survey. 

Difference of DEMs (DoDs) were created by subtracting one DEM from another. Common extents were required for comparison of the DoDs. For the gully, a modified region grow approach was applied to an unclipped RIEGL DEM. This approach utilises a difference from mean elevation (DFME) (Evans and Lindsay, 2010) and a slope layer to detect the gully edges. A 50 cm buffer was then applied to ensure full capture of the gully edges. 

This dataset also includes hillshading derived from the DEMs. The original point cloud data is not available for download from the eAtlas (due to its large size), but is available on request from the Point of Contact. 

The DEMs are available for the following years and sites:
Meadowvale: 2017, 2018, 2019
Minnievale: 2016, 2017, 2018, 2019
Strathbogie: 2016, 2017, 2018, 2019
Virginia Park: 2016, 2017, 2018, 2019

The DoDs correspond to the difference between the current year and the base year. 

Limitations of the data:

Minimum Z DEM’s for representation of geomorphology ignore the possibility of overhangs. The raw DEMs provided include an area larger than the mapped gullies. These areas contain many anomalies as the scans were not intended to fully capture these areas. As a result the DEMs need to be masked before analysis is applied.

Format:

This dataset consists of multiple ZIP files containing LAZ files, ArcGIS shapefiles, JPGs and geoTIFF format grids
Point_Clouds contains four folders, one for each paired Control/Treamenet gully monitoring site. Each folder contains Control and Treatment subfolders with zip files of the georeferenced TLS scans (as LAZ) by year. The file name convention is explained in the data dictionary. 
DEMs_and_DODs contains four ZIP files (one for each property) containing the DEMs and DEM of difference respectively in geoTIFF format at each control and treatment site for up to 5 years of monitoring between 2015 and 2019.
   File names For DEMs:  _DEM5cm.TIFF
   File names For Shaded relief DEMs: _DEM5cm_HS.TIFF
   Where  is the 3 letter site code (see data dictionary) 
   and  is the year surveyed
  (actual survey dates are captures in the naming convention of the Point Cloud files)
NESP_2017_controlpoints_28355.shp contains the locations of the reference markers used for georeferencing the surveys.
_META contains four zip files (one for each property) containing the DEMS and DODs in figures 21, 28, 36, and 44of the NESP report Bartley et al., 2019)
All coordinates are GDA94 MGA zone 55.

Data Dictionary:

File naming convention for the Point clouds zip files (and LAZ files) 
_[_optional][.suffix] 
 codes used:
gp = ground platform 
v1 = Riegl VZ-400 
dr = time-of-flight discrete return lidar 
 - latitude longitude in decimal degrees
 - YYYYMMDDTTTTTT

ba3 = point clouds 
bc4 = Interpolated minimum heights to regular grid with median filtered applied
m5 zone 55

The return deviation is stored in the ‘point_source_id’ field of the LAZ files and
and the range is stored in the ‘GPS_time’ field.

File naming Conventions for DEMs and DOD’s
Site_Code used for file names are as follows:
MIN = Minnievale
MV = Meadowvale
MW = Mount Wickham
SB = Strathbogie
VP = Virginia Park
 - Treatment/Control
Note: 
SBT is now the Strathbogie Control site 
SBC (to 2018) and SBT2 (after 2018) is now the Strathbogie Treatment site
 = year measured
DEM5cm = 5 cm gridded digital elevation model of ground surface 
DEM5cm_HS = hillshade of DEM
DoD_- = DEM of difference
Mask = mask showing extents used for DoD 

References:

Bartley, R., Hawdon, A., Henderson, A., Wilkinson, S., Goodwin, N., Abbott, B., Bake, B., Boadle, D., and Ahwang, K. (2019) Quantifying the effectiveness of gully remediation on off-site water quality: preliminary results from
demonstration sites in the Burdekin catchment (third wet season). Report to the National Environmental Science Programme. Reef and Rainforest Research Centre Limited, Cairns (115 pp.).

Bartley, R., Goodwin, N., Henderson, A.E., Hawdon, A., Tindall, D., Wilkinson, S.N. and Baker, B., 2016. A comparison of tools for monitoring and evaluating channel change, Project 1.2b. Report to the National Environmental Science Programme. Reef and Rainforest Research Centre Limited, Cairns (36pp.).

NR Goodwin, J Armston, I Stiller, J Muir.  (2016) Assessing the repeatability of terrestrial laser scanning for monitoring gully topography: A case study from Aratula, Queensland, Australia, Geomorphology 262, 24-36.

Data Location:

This dataset is filed in the eAtlas enduring data repository at: data\NESP2\2.1.4_Gully_Remediation_Effectiveness

Organization: Australian Ocean Data Network