Chapter 7
AIRBORNE LASER ALTIMETRY FOR PREDICTIVE MODELING OF
COASTAL STORM-SURGE FLOODING
TIM L. WEBSTER
1 AND DONALD L. FORBES
2
1 Applied Geomatics Research Group, Center of Geographic Sciences, Nova Scotia
Community College, 50 Elliot Road, RR# 1 Lawrencetown, Nova Scotia, Canada B0S
1M0
2 Geological Survey of Canada, Bedford Institute of Oceanography, P.O. Box 1006,
Dartmouth, Nova Scotia, Canada B2Y 4A2
1. Introduction
1.1 THE CHALLENGE
Next to fire, floods are the most common and widespread natural disasters. For
coastal communities, the risk of flooding associated with sea-level rise and storm
surges is of particular concern. Global mean sea-level has been rising at a rate between
0.1 and 0.2 m per century over the past 100 years (McLean et al., 2001). The
Intergovernmental Panel on Climate Change (IPCC) has predicted a further increase of
0.09 to 0.88 m, with a central value of 0.48 m, from 1990 to 2100 (Church et al., 2001).
Adjusted to a 100 year base, the central value (0.44 m) is between 2.2 and 4.4 times the
global mean rate of sea-level rise during the 20th century, implying an acceleration in
response to global warming. This will result in more frequent extreme high water levels
(storm-surge flood levels) and the return interval for a given flood level may be further
reduced by potential increases in storm intensity (e.g. Walsh and Katzfey, 2000).
Relative sea-level rise at any one place is a combination of changes in regional sealevel and vertical ground motion. Subsidence in many coastal areas will result in more
rapid relative sea-level rise. Projections of the number of people potentially subject to
storm-surge flooding on an annual basis increase from about 10 million today to 50-80
million in the 2080s, depending on adaptive response and population growth, and
assuming a sea-level rise comparable to the central value of the IPCC projections
(Nicholls et al., 1999). This points to the need for mapping of flood risk hazard zones in
areas of low relief where existing maps are rarely adequate. A high-resolution digital
elevation model (DEM) produced using airborne laser altimetry (LIDAR) provides a
cost-effective and efficient method to achieve this end. These types of maps and
information products provide the background required for coastal zone managers to
make policy decisions related to future developments, as well as adaptation possibilities
to mitigate damage and loss of existing coastal resources.
Superimposed on sea-level rise, coastal erosion and flooding associated with large
waves and runup riding on high storm-surge water levels pose additional hazards. Other
factors being equal, coastal erosion will increase with a rise in mean sea-level (Bruun,
1962; Cowell and Thom, 1994; Leatherman et al., 2003). On dune-backed coastal
beaches and barriers, erosion often takes the form of dune-front scarping, while
backshore flooding may occur if runup and overwash exploit low points in the dune
crest to create breaches and washover channels. The potential for breaching is difficult
to assess, but availability of a high-resolution DEM from LIDAR surveys would enable
157
and Management Applications, 157-182.
© 2006 Springer. Printed in the Netherlands.
L.L. Richardson and E.F. LeDrew (eds.), Remote Sensing of Aquatic Coastal Ecosystem Processes: Science
AIRBORNE LASER ALTIMETRY FOR PREDICTIVE MODELING OF
COASTAL STORM-SURGE FLOODING
TIM L. WEBSTER
1 AND DONALD L. FORBES
2
1 Applied Geomatics Research Group, Center of Geographic Sciences, Nova Scotia
Community College, 50 Elliot Road, RR# 1 Lawrencetown, Nova Scotia, Canada B0S
1M0
2 Geological Survey of Canada, Bedford Institute of Oceanography, P.O. Box 1006,
Dartmouth, Nova Scotia, Canada B2Y 4A2
1. Introduction
1.1 THE CHALLENGE
Next to fire, floods are the most common and widespread natural disasters. For
coastal communities, the risk of flooding associated with sea-level rise and storm
surges is of particular concern. Global mean sea-level has been rising at a rate between
0.1 and 0.2 m per century over the past 100 years (McLean et al., 2001). The
Intergovernmental Panel on Climate Change (IPCC) has predicted a further increase of
0.09 to 0.88 m, with a central value of 0.48 m, from 1990 to 2100 (Church et al., 2001).
Adjusted to a 100 year base, the central value (0.44 m) is between 2.2 and 4.4 times the
global mean rate of sea-level rise during the 20th century, implying an acceleration in
response to global warming. This will result in more frequent extreme high water levels
(storm-surge flood levels) and the return interval for a given flood level may be further
reduced by potential increases in storm intensity (e.g. Walsh and Katzfey, 2000).
Relative sea-level rise at any one place is a combination of changes in regional sealevel and vertical ground motion. Subsidence in many coastal areas will result in more
rapid relative sea-level rise. Projections of the number of people potentially subject to
storm-surge flooding on an annual basis increase from about 10 million today to 50-80
million in the 2080s, depending on adaptive response and population growth, and
assuming a sea-level rise comparable to the central value of the IPCC projections
(Nicholls et al., 1999). This points to the need for mapping of flood risk hazard zones in
areas of low relief where existing maps are rarely adequate. A high-resolution digital
elevation model (DEM) produced using airborne laser altimetry (LIDAR) provides a
cost-effective and efficient method to achieve this end. These types of maps and
information products provide the background required for coastal zone managers to
make policy decisions related to future developments, as well as adaptation possibilities
to mitigate damage and loss of existing coastal resources.
Superimposed on sea-level rise, coastal erosion and flooding associated with large
waves and runup riding on high storm-surge water levels pose additional hazards. Other
factors being equal, coastal erosion will increase with a rise in mean sea-level (Bruun,
1962; Cowell and Thom, 1994; Leatherman et al., 2003). On dune-backed coastal
beaches and barriers, erosion often takes the form of dune-front scarping, while
backshore flooding may occur if runup and overwash exploit low points in the dune
crest to create breaches and washover channels. The potential for breaching is difficult
to assess, but availability of a high-resolution DEM from LIDAR surveys would enable
157
and Management Applications, 157-182.
© 2006 Springer. Printed in the Netherlands.
L.L. Richardson and E.F. LeDrew (eds.), Remote Sensing of Aquatic Coastal Ecosystem Processes: Science