multi-flow directions in anudem michael hutchinson fenner school of environmental and society...
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Multi-flow directions in ANUDEM
Michael Hutchinson
Fenner School of Environmental and SocietyAustralian National University
Contents
• Background – the 9 Second Australian continental DEM
• ANUDEM – locally adaptive multigrid method
• Multiple data sources – points, contours, lakes, streams, cliffs
• Major anabranches and braided stream networks
• Implementation in ANUDEM
• Current and future progress
History of Australian DEMs1976-82 First coarse scale Aust DEM - BMR 1965-88 Digitising 1:100K maps - AUSLIG 1983-88 Early development of ANUDEM 1991 First drainage enforced 90 second Aust DEM 1996 9 second DEM Version 1 1998 National Wild Rivers Study - CRES 1988-00 Further development of ANUDEM 2001 9 second DEM Version 2 – with AUSLIG 2001-08 Further development of ANUDEM 2005-08 9 second DEM Version 3 – with Geoscience Australia
9 Second Australian DEM Version 3 2008
Maximum elevation error as functions of cumulative percentage area of the
continent
0
20
40
60
80
100
120
140
160
180
200
0 10 20 30 40 50 60 70 80 90 100Cumulative Percentage Area
Ele
vatio
n E
rror
(m
) Maximum Standard Error
Maximum Absolute Error
Input DataPoint elevations
Sink points Streamlines
Boundary polygons Contours
Lake polygonsCliff lines
Data mask polygons
ANUDEM
Diagnostic FilesSinks
Large residuals Stream and cliff errors
Derived streamlinesDerived cliff lines
Digital Elevation Model
Flow direction gridAspect grid
Mapping Tool GIS
Error Correction
Input DataPoint elevations
Sink points Streamlines
Boundary polygons Contours
Lake polygonsCliff lines
Data mask polygons
ANUDEM
Diagnostic FilesSinks
Large residuals Stream and cliff errors
Derived streamlinesDerived cliff lines
Digital Elevation Model
Flow direction gridAspect grid
Mapping Tool GIS
Error Correction
Data Flows for ANUDEM Elevation Gridding Program
Cliff (red) and streamline (blue) data
Automated adjustment of streams and cliffs to represent morphology
Major anabranching systems – Darling River
Major anabranching systems – Murray, Murrumbidgee
Braided Stream Networks
ANUDEM representation of braided stream network
With multi-flow directions
Without multi-flow directions
Very complex braided streams
Two multi-flow grid directions is not enough
Heights not reliable in determining major branches
Conclusions
Up to two flow directions at each stream grid point can represent major anabranching networks
Not always insufficient for complex braided networks
Additional branches required to respect full connectivity of stream data networks – needed for reliable hydrological and catchment analyses – such as revised pfafstedder systems (Janet Stein)
Revised grid flow direction structures needed
Stream heights not reliable in determining principal flow directions
Somewhat distinct from possible representation of multi-flow directions on general hillslopes