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May 2013 Issue

Advances in Aerial Imagery Benefit Coastal Zones
By Steven Apfelbaum

Predicted increases in the intensity of storms, battering waves and storm surges suggest greater meteorological variability in the tributary coastal-zone watersheds, as well as the need for updated coastal environment assessment tools.

Among the new tools, for instance, is a defense-grade, multispectral, ultrahigh-resolution aerial imaging camera that is currently measuring changes in coastal zones and mapping many natural resource features (e.g., sedimentation and turbidity, substrate conditions, vegetation, oyster reefs, fishery habitats) in estuaries, lakes, and tributary rivers and streams in the Great Lakes and Gulf Coast. The imaging tool has been used to map ocean bottom conditions down to several meters depth in these areas and can augment sampling from boats.

Mapping of storm damages can be used to help plan and measure recovery after natural disasters. In tributary watersheds, this imagery can measure storm damage to homes, assess the infrastructure necessary for communities to operate, and help determine future risks, insurance and other costs under changing environmental conditions. Mapping can also show damage to forests, channel and bank instability of shorelines and tributary rivers, and that state of barrier islands and coastal buffers such as wetlands. For instance, multispectral imagery and on-the-ground measurements can be correlated with image analysis to determine which coastal barrier islands destroyed by Hurricane Sandy should be restored to offer future coastal protection.

Precise mapping of tributary watersheds, water quality, potable water supply risks and potential environmental contaminant sources is essential for managing future coastal risks. Monitoring sediment deposits, contaminant depositions and erosion sources is key to reducing flooding risks. Drought, crop failures and volatility in stormwater runoff shown via GIS watershed modeling can help document expected increased erosion, and sedimentation and nutrient contributions to coastal waterways.

Ultrahigh-resolution, multispectral imagery allows for shooting images during narrow windows of time, which could be imperative, for instance, right after a storm event to map runoff conditions, or during a coastal algal bloom. Such imagery could be obtained by flying low and slow, even under lower-light conditions, such as beneath cloud cover.

New camera technology, such as the Leica RD 30, enables high-resolution crystal clarity and registration among all bands, or wavelengths of radiation, such as infrared and green bands. This requires the use of only one camera and a split beam of incoming light radiation that feeds each of the sensors, which are the cameras that receive and record the individual wavelength bands.

Conventional camera technology uses an individual camera head for each wavelength obtained during a multispectral-imaging flight, and each camera requires independent calibration and alignment, and often changes in shutter speed depending on the resolution, flying altitude and airplane speed over ground.

New technology requires only one camera head to calibrate, align and manage any specific changes (e.g., shutter speed, filters, cleaning) that are necessary or desirable for acquiring a target.

The single light-beam splitter and camera head technology approach provides for automated band registration, and faster and highly precise image processing (e.g., mosaicking, orthorectification, color normalization). This technology is, therefore, an efficient candidate for use on many ecological targets.

Challenges do exist, however, in using this technology, including achieving perfect timing, dealing with the effects of changing environmental conditions and how to optimize uses of the imagery.

From creating maps to site new industrial operations to monitoring pipelines and being used in a myriad of scientific investigation activities, ultrahigh-resolution, multispectral imagery will benefit the future of coastal environments. For example, use of the infrared band, combined with several other bands allows wetlands, poor soils and floodplain environments to be mapped quickly and efficiently for siting and design or restoration of facilities. This provides accurate data for projects and saves considerable field time and costs.

Ultrahigh-resolution, multispectral imagery can also be used to map coastal dynamics and invasive plant species that are colonizing coastal wetlands. Some species colonize in the wake of storm surge, such as the spread of a European genetic strain of giant reed grass (Phragmites communis). Because there is increasing evidence that this species weakens the buffering ability of coastal wetlands, accurately understanding such patterns of change can provide information needed to address it.

Advances in aerial imagery can be used to help understand coastal restoration needs. The availability of this imagery also enables regulators, designers, scientists and others to share data, which builds trust in interoperational efforts. This is necessary to prepare for challenging times ahead in coastal zones.

Many questions are being asked about the future of coastal areas. Should humans retreat, install barriers, resign to natural disasters and/or rethink infrastructure investments in these zones?

What is clear is that the future will depend on obtaining accurate information to make predictions and develop responses to the changing environment.

Steven Apfelbaum is the founder of and principal ecologist at Applied Ecological Services Inc. (Brodhead, Wisconsin), an environmental restoration firm with 10 offices in the U.S. and two abroad. He is the author of Nature’s Second Chance and co-author of the Restoring Ecological Health to Your Land series on how to design and implement small-scale environmental restoration.


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