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High-Resolution Elevation and Image Data Within the Bay of Fundy Coastal Zone, Nova Scotia, Canada
Abstract
The Applied Geomatics Research Group (AGRG) is a component of the Centre of Geographic Sciences (COGS) located in the Annapolis Valley, Nova Scotia. Its mandate is the application of geomatics technology for environmental research within Maritime Canada. In the fall of 1999 and summer of 2000 a large data acquisition campaign was initiated to collect high-resolution elevation and other remotely sensed image datasets along the Bay of Fundy coastal zone (Figure 15.1 and colour insert following page 164). The purpose of the research was to evaluate their effectiveness in obtaining critical information about the coastal zone, particularly data to be used to assess flood-risk potential associated with storm surge events. Global mean sea level has been increasing between 0.1 and 0.2 meters per century. With increasing greenhouse gases, sea level rise is expected to accelerate and the Intergovernmental Panel on Climate Change predicts that global average sea level may increase by 0.09 to 0.88 meters by 2100, placing the lives and property of an estimated 46 million people at risk (Houghton et al., 2001). The Bay of Fundy is no exception: relative sea-level is rising in this region by an estimated rate of 2.5 cm per century and many coastal areas are becoming more susceptible to flooding from storm events (Stea, Forbes, and Mott, 1992). In addition to sea level rise, storm surge and ocean waves are also factors at the coastline and are carried to higher levels on rising mean sea level. Storm surge in general is defined as the algebraic difference between the observed water level and the predicted astronomical level as one would find in tide tables. With possible increased storminess associated with climate change, the next 100 years will probably see more frequent flooding of coastal zones, and an increase in erosion of coastal features. With the recent increase in the spatial resolution of geomatics data available, both multispectral imagery (Ikonos, Quickbird, CASI) and high accuracy elevation data, landuse planners and policy makers now have access to the information required to manage the coastal zone.
... Applications to coastal process studies in the United States have been reported by Sallenger et al. (1999) and Krabill et al. (1999), among others. Preliminary trials in Atlantic Canada were reported by O'Reilly (2000), and subsequent experience was described by Webster et al. (2002; 2004a; 2004b), O'Reilly et al. (2005), and Webster and Forbes (2006). Most of the coast of the conterminous United States has now been mapped using this technology (Brock et al., 2002). ...
... The maps depicting areas vulnerable to sea-level rise have been used to assess potential impact to ecosystems such as salt marshes and coastal dunes and cultural features such as homes, businesses, municipal infrastructure, and historic sites in lowlying areas. This project builds on the experience gained from the successful application of lidar technology to storm-surge flood-risk mapping on Prince Edward Island (McCulloch et al., 2002; Webster et al., 2001; 2004a; 2004b; Webster and Forbes, 2006). ...
... PCI Geomatica™ software is used for the visualization and to generate the individual frames for the animations. In previous studies (Dickie, 2001; Webster et al., 2004a; 2004b; MacKinnon, 2004), a solid colour was used to represent the water level. In this study we modified this method to allow the water to be transparent so that the underlying features affected by the floodwater are still visible. ...
Coastal flooding from storm-surge events and sea-level rise is a major issue in Atlantic Canada. Airborne light detection and ranging (lidar) has the spatial density and vertical precision required to map coastal areas at risk of flooding from water levels typically 1-2 m higher than predicted tides during storm surges. In this study, a large section of the New Brunswick coast along Northumberland Strait was surveyed in 2003 and 2004 using two lidar systems. Water levels from a major storm-surge event in January 2000 were surveyed using a global positioning system (GPS) and used as a benchmark for flood-risk maps. Maps of flood depth were also generated for all water levels and used for socioeconomic and ecosystem impact assessment. Flood-risk maps were constructed using standard geographical information system (GIS) processing routines to determine the spatial extent of inundation for a given water level. The high resolution of the lidar digital elevation model (DEM) captured embankments such as raised roadbeds that could prevent flooding inland. Where connectivity was present due to culverts or bridges, the DEM was notched across the roadbed to simulate the connection between the ocean and upstream low-lying areas in the GIS. An automated routine was then used to generate maps of flood extent for water levels at 10 cm increments from 0 to 4 m above mean sea level. Validation of the flood-risk and flood-depth maps for the January 2000 storm-surge water level by field visits indicates that the simulations are generally accurate to within 10-20 cm. The lidar data were also used to evaluate the potential for overtopping and dune erosion on a large coastal spit, La Dune de Bouctouche. This showed a high vulnerability to storm damage for critical habitats on the spit. The lidar-derived maps produced in this study are now available to coastal communities and regional planners for use in the planning process and to assist in development of long-term adaptation strategies.
... The 1-D model is best used to represent hydraulic flow through the channel, while the 2-D model is required for spatially distributed results, such as flood inundation maps [19]. Previous coupled 1-D/2-D modeling studies of coastal flooding focus on the failure of sea defense mechanisms [20,21], and Brown et al. [20] and Webster et al. [22] note the significance of forcing inputs, such as coastal water levels, to model outcome, and cite the ongoing issue of model sensitivity to spatial resolution of the grid. In this study, we have not focused on variations in grid density for the large domain, but rather in selected areas with the goal of achieving our desired flood inundation mapping precision for the town while keeping the CPU calculation time reasonable for each simulation. ...
... Flood risk mapping that accounts for the combined effect of sea-level rise and storm surge shows that the Bridgewater Mall, which was built on marshland, is especially vulnerable to flooding, along with several key transportation routes and parkland. In our study we confirmed the importance of elevated coastal water levels emphasized by [20,22] for increasing the risk of flooding for areas located inland from the coast. This type of coupled 1D-2D model is important for many communities that are located along estuaries and not directly on the coast. ...
Bridgewater, Nova Scotia, is located 20 km inland from the mouth of the LaHave River estuary on the Atlantic Coast of Canada. Bridgewater is at risk of flooding due to the combined effects of river runoff and a storm surge on top of high tide. Projected increases in sea-level and possible increased river runoff with climate change increase the risk of future flooding. A set of river and ocean water level simulations were carried out to determine the risk of flooding to Bridgewater today and in the future under climate change. The hydrodynamic simulation developed incorporates return periods of a time series of river discharge measurements for the LaHave watershed, ocean water dynamics at the mouth of the river under normal tidal conditions and with two levels of storm surge, near shore and river bathymetry, as well as high precision topographic lidar derived ground elevations and survey grade GPS. The study was supported by data from two tide gauge sensors, and qualitative evidence provided by the community such as historical flood levels and photographs. Results show that areas upstream of the town are vulnerable to large discharge events of the LaHave River. The downtown waterfront and infrastructure are not susceptible to fluvial flooding, but is vulnerable to sea-level rise and storm surge flooding.
... 1905-1925, 1970-1990) to a reduced hurricane activity. The increase in strong hurricanes since the 1970s is however mostly attributed to higher water temperatures as a result of climate change, as indicated amongst others by the strong correlation between the energy dissipation index and water temperatures (Emanuel 2005;Goldenberg et al. 2001;Trenberth et al. 2007;Webster et al. 2005). In contrast, the overall number of hurricanes has decreased during the period 1957-2004 (Ren et al. 2006). ...
Adaptation to climate change will be a necessity for coastal zones in decades and even centuries to come. Although adaptation to climate and environmental changes has been a feature of human societies since the evolution of modern humans, current challenges posed by climate change and sea level rise in a crowded and developed world are of a vaster nature of those faced by humanity before and will necessitate new approaches, new techniques and new strategies. A conceptual framework is being developed, centered on the notions of vulnerability, adaptation and resilience. Adaptation to climate change will necessitate international cooperation and coherent strategies, although solutions will need to be developed with respect to local circumstances. The main strategies—protection, accommodation, retreat and precaution, are declined in various tools of technical, scientific, legislative, administrative, social or physical nature.
It is widely recognised that organisations involved in coastal management must take steps to improve the ways in which stakeholders and the public are involved in coastal decision-making. In particular, there needs to be more emphasis on improving participation, consultation, and information provision throughout the process. In recognition of this, there is a need to develop new techniques that could aid the communication of coastal information to the public. It has been suggested that some of these techniques might involve the use of Geographical Information Systems (GIS). Whilst GIS are widely used by coastal managers, their application is hampered by the highly technical output that they often produce. However, the advent of a new type of system known as virtual reality GIS enables the likely effects of coastal management decisions to be presented in a format that is suitable for widespread consultation and dissemination. A proposed managed realignment scheme on the north Norfolk coast, England, is used to describe an integrated GIS methodology allowing the production of virtual reality representations of the current site environment and simulations of what might be present after the intervention. Both static and user-navigable visualisations have been produced because these lend themselves to both paper and electronic publication. Comparisons between the alternative methods are presented along with a discussion of the technical, user, and institutional issues surrounding the potential application of the methodology. It is argued that the techniques presented have the potential to stimulate meaningful discussion during the consultation process, although further research is still required to determine the exact form this might take.
In the summer of 2000, the Annapolis Valley of Nova Scotia, Canada was selected for a high‐resolution elevation survey utilizing LIDAR (Light Detection And Ranging). Two different LIDAR systems were used to acquire data for the area. The vertical accuracy specification for the survey called for heights to be within an average of 15 cm of measured GPS heights and 95% of the data to be within 30 cm. Prior to the application of these data to geoscientific problems, extensive validation procedures were employed. High precision GPS and traditional surveys were conducted to collect height validation checkpoints. Two validation methods were developed in a GIS environment that involved comparing the checkpoints to the original LIDAR points and to an interpolated “bald earth” DEM. A systematic height error between flight lines for one of the LIDAR methods was detected that related to the calibration procedures used in the survey. This study highlights the differences between laser systems, calibration and deployment methodologies and emphasizes the necessity for independent validation data.
A significant portion of the Canadian Maritime coastline has been surveyed with airborne Light Detection and Ranging (LiDAR). The purpose of these surveys has been to map the risk of flooding from storm surges and projected long-term sea‑level rise from climate change and to include projects in all three Maritime Provinces: Prince Edward Island, New Brunswick, and Nova Scotia. LiDAR provides the required details in order to map the flood inundation from 1 to 2 m storm surge events, which cause coastal flooding in many locations in this region when they occur at high tide levels. The community of Annapolis Royal, Nova Scotia, adjacent to the Bay of Fundy, has been surveyed with LiDAR and a 1 m DEM (Digital Elevation Model) was constructed for the flood inundation mapping. Validation of the LiDAR using survey grade GPS indicates a vertical accuracy better than 30 cm. A benchmark storm, known as the Groundhog Day storm (February 1–3, 1976), was used to assess the flood maps and to illustrate the effects of different sea-level rise projections based on climate change scenarios if it were to re-occur in 100 years time. Near shore bathymetry has been merged with the LiDAR and local wind observations used to model the impact of significant waves during this benchmark storm. Long-term (ca. greater than 30 years) time series of water level observations from across the Bay of Fundy in Saint John, New Brunswick, have been used to estimate return periods of water levels under present and future sea-level rise conditions. Results indicate that under current sea-level rise conditions this storm has a 66 year return period. With a modest relative sea-level (RSL) rise of 80 cm/century this decreases to 44 years and, with a possible upper limit rise of 220 cm/century, this decreases further to 22 years. Due to the uncertainty of climate change scenarios and sea-level rise, flood inundation maps have been constructed at 10 cm increments up to the 9 m contour which represents an upper flood limit estimate in 100 years, based on the highest predicted tide, plus a 2 m storm surge and a RSL of 220 cm/century.
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