5. Conclusions
This work demonstrates the application of LIDAR technology to the mapping of
storm-surge flood risk for coastal areas. The high-resolution of the LIDAR data allowed
a DEM to be constructed that can now be used to model the inundation effect of water
levels of 2 m or more higher than usual. However, the results of this study also
demonstrate the need for independent validation data to ensure the reliability of such
high-resolution topographic mapping.
Careful analysis of validation data using several different approaches revealed the
presence of an altitude calibration bias in the LIDAR elevations for the present study. A
bulk adjustment of the elevations by 0.9 m provided a reasonable representation of
flood levels, but variation in the flying altitude between flight lines resulted in failure to
meet the intended 0.3 m vertical error specification. This was partially mitigated by the
density of survey points, so that the mean elevation determined for each small grid cell
was more often within specification. New LIDAR surveys recently undertaken in
another coastal area of eastern Canada are building on the lessons learned in the Prince
Edward Island study to provide more accurate and precise DEM data. Nevertheless, the
LIDAR data obtained in Prince Edward Island provided unprecedented topographic
detail and enabled highly detailed delineation of flood hazard zones. The flood risk
maps and information products have made it to the hands of the coastal resource
managers, who have to deal with these risks on an annual basis, and have been
incorporated into their GIS system. The maps have provided a tool to allow the local
planning officials to begin a long-term adaptation process, and to initiate community
discussions. For the short term, planning officials now use the maps to inform local
developers of the future predictions of flooding events and possible water depths
associated with different areas of the waterfront. The planning department has used the
information to identify areas where development may be restricted along the waterfront
because of the risk of flooding.
6. Acknowledgements
We are happy to acknowledge the efforts of the data acquisition contractors,
including Rick Quinn, Roger Shreenan and others (Terra Remote Sensing Inc.), Herb
Ripley, Andrew Cameron, and Laura Roy (Hyperspectral Data International), the pilots
and other support staff. We thank Paul Fraser and Dan Deneau (Applied Geomatics
Research Group, Centre of Geographic Sciences, NSCC) for the Charlottetown GPS
campaign and preliminary analysis. We would like to acknowledge George Dias and
the other members of the AGRG class (2002) for coding the ARC AML that does the
comparison between GPS points and LIDAR points within a fixed radius. We are also
grateful to Steve Dickie for his work on the LIDAR processing and report for the PEI
project. We acknowledge the contributions of Mike Butler and Brent Rowley for
helping in the coordination of data acquisition during the summer of 2000. Gavin
Manson (Geological Survey of Canada) provided critical field and office support. Glen
King (CHS) assisted with vertical control data, as did Charles O’Reilly (CHS), who
was the prime inspiration behind the initiative to acquire laser altimetry for this project.
Don Poole (Planning and Development Officer, City of Charlottetown) provided
invaluable assistance. This study was funded in large part by the Climate Change
Action Fund (CCAF) of the Government of Canada and we are grateful to the entire
CCAF project team for their ideas and support on the project. Additional funding to the
179
Airborne Laser Altimetry
This work demonstrates the application of LIDAR technology to the mapping of
storm-surge flood risk for coastal areas. The high-resolution of the LIDAR data allowed
a DEM to be constructed that can now be used to model the inundation effect of water
levels of 2 m or more higher than usual. However, the results of this study also
demonstrate the need for independent validation data to ensure the reliability of such
high-resolution topographic mapping.
Careful analysis of validation data using several different approaches revealed the
presence of an altitude calibration bias in the LIDAR elevations for the present study. A
bulk adjustment of the elevations by 0.9 m provided a reasonable representation of
flood levels, but variation in the flying altitude between flight lines resulted in failure to
meet the intended 0.3 m vertical error specification. This was partially mitigated by the
density of survey points, so that the mean elevation determined for each small grid cell
was more often within specification. New LIDAR surveys recently undertaken in
another coastal area of eastern Canada are building on the lessons learned in the Prince
Edward Island study to provide more accurate and precise DEM data. Nevertheless, the
LIDAR data obtained in Prince Edward Island provided unprecedented topographic
detail and enabled highly detailed delineation of flood hazard zones. The flood risk
maps and information products have made it to the hands of the coastal resource
managers, who have to deal with these risks on an annual basis, and have been
incorporated into their GIS system. The maps have provided a tool to allow the local
planning officials to begin a long-term adaptation process, and to initiate community
discussions. For the short term, planning officials now use the maps to inform local
developers of the future predictions of flooding events and possible water depths
associated with different areas of the waterfront. The planning department has used the
information to identify areas where development may be restricted along the waterfront
because of the risk of flooding.
6. Acknowledgements
We are happy to acknowledge the efforts of the data acquisition contractors,
including Rick Quinn, Roger Shreenan and others (Terra Remote Sensing Inc.), Herb
Ripley, Andrew Cameron, and Laura Roy (Hyperspectral Data International), the pilots
and other support staff. We thank Paul Fraser and Dan Deneau (Applied Geomatics
Research Group, Centre of Geographic Sciences, NSCC) for the Charlottetown GPS
campaign and preliminary analysis. We would like to acknowledge George Dias and
the other members of the AGRG class (2002) for coding the ARC AML that does the
comparison between GPS points and LIDAR points within a fixed radius. We are also
grateful to Steve Dickie for his work on the LIDAR processing and report for the PEI
project. We acknowledge the contributions of Mike Butler and Brent Rowley for
helping in the coordination of data acquisition during the summer of 2000. Gavin
Manson (Geological Survey of Canada) provided critical field and office support. Glen
King (CHS) assisted with vertical control data, as did Charles O’Reilly (CHS), who
was the prime inspiration behind the initiative to acquire laser altimetry for this project.
Don Poole (Planning and Development Officer, City of Charlottetown) provided
invaluable assistance. This study was funded in large part by the Climate Change
Action Fund (CCAF) of the Government of Canada and we are grateful to the entire
CCAF project team for their ideas and support on the project. Additional funding to the
179
Airborne Laser Altimetry