Remote Sensing and Modeling

Advances in sensor design and data analysis techniques are making remote sensing systems suitable for monitoring coastal ecosystems and their changes. Hyperspectral imagers, LiDAR and radar systems are available for mapping coastal marshes, submerged aquatic vegetation, coral reefs, beach profiles, algal blooms, and concentrations of suspended particles and dissolved substances in coastal waters. Since coastal ecosystems have high spatial complexity and temporal variability, they benefit from new satellites, carrying sensors with fine spatial (0.4–4 m) or spectral (200 narrow bands) resolution. Imaging radars are sensitive to soil moisture and inundation and can detect hydrologic features beneath the vegetation canopy. Multi-sensor and multi-seasonal data fusion techniques are significantly improving coastal land cover mapping accuracy and efficiency. Using time-series of images enables scientists to study coastal ecosystems and to determine long- term trends and short- term changes.

Mapping seafloor environments on the continental shelf, over the past several decades, has undergone rapid transitions from early, relatively low-resolution techniques, such as echo sounding in deeper waters and digital aerial photography in shallower waters, to modern advancements like high-density airborne laser bathymetry and multi-spectral satellite imagery that can now detect seafloor reflectance at depths ranging to 50–60 m. Passive imaging systems require clear waters that typically exist on carbonate banks in many regions of the world ocean. Carbonate banks in the south Florida region provide nearly ideal conditions for mapping submarine topography and interpreting geomorphological and biophysical environments. A hierarchical open-ended classification system was developed for both open-ocean and key (low carbonate islands) environments. These classification systems, which are based on cognitive recognition of seafloor features interpreted from LADS and IKONOS imagery, are directly applied in GIS cartography programs to create comprehensive, informative, and interactive products. Examples from the open ocean southeast coast and Marquesa Islands illustrate the applicability and usefulness of advanced remote sensing techniques intercalated with GIS programs and classificatory schema for organizing seafloor typologies. This new technology and its associated classification systems permit major advancements in the detailed mapping of seafloors that have never before been achieved for margins of regional seas.

Over the last decade, there has been a proliferation of commercially available tripod-mounted Terrestrial Laser Scanner (TLS) systems that use the phase difference or the time-of-flight of emitted pulses of light to rapidly acquire high-density topographic and surface reflectance data. These TLS systems have been well received in the Earth science community because of their ability to collect 10²–10⁵ measurements per second of azimuth, zenith, distance, intensity, and surface color data at distances ranging from 10⁰ to 10³ m. A TLS instrument’s portability, ease of use, and rate of data collection opens the possibility of collecting detailed topographic data at sites where such surveys may not have been possible before. The application of TLS data to current Earth sciences research has allowed us to better understand of the character, timing, rates, and spatial scales of different processes that have been difficult, if not impossible, to evaluate using traditional survey techniques. However, the successes achieved with TLS systems in certain projects may result in unrealistic expectations regarding the density and quality of data that can reasonably be achieved in different settings. This chapter seeks to orient potential or experienced TLS users to its applicability in above-water coastal settings. An emphasis is placed on providing insight into both the variety of current research using TLS data, as well as the compromises in spatial resolution that necessarily arise from field conditions and survey design.

Remote sensing emerges as a very effective technique to capture the dynamics of the coastal system, as it provides a holist view of the system at a wide range of spatial and temporal scales. However, the recent thrive of these systems has led to a broad variety of sensors and data, which can difficult the choice of the optimal sensor for a practical application. In mesoscale coastal environment applications and considering the universe of the solutions, Landsat program arises as a good compromise between spectral, radiometric, spatial and temporal resolutions, combined with free data access, supported by an efficient data sharing platform. The capabilities of the Landsat program was recently extended with the launch of a new satellite – Landsat 8, with improved radiometric and spectral resolution, opening the door to new studies. This work describes the applicability of these images in four case studies that demonstrates the potentialities of the Landsat program in what concerns: (1) time coverage – long-term evolution of an ephemeral ebb delta island; (2) frequency of coverage – seasonal evolution of a short-lived beach; (3) radiometric resolution – shoreline detection and extraction; (4) spectral resolution – bathymetric data retrieval.

A new paradigm has emerged for management of coral reefs in an era of changing climate – managing for resilience. A fundamental need for such management to be effective is our ability to measure and map coral reef resilience. We review the resilience concept and factors that may make a coral reef more or less resilient to climate-driven impacts, and focus on recent advances in a trio of technologies – remote sensing, spatial distribution modeling, and ecosystem simulation – that promise to improve our ability to quantify coral reef resilience across reefs. Remote sensing allows direct mapping of several ecosystem variables that influence reef resilience, including coral and algal cover, as well as a range of coral reef stressors, as exemplified by three case studies. Spatial distribution modeling allows exploitation of statistical relationships between mappable environmental variables and factors that influence resilience but which cannot be mapped directly, such as herbivore biomass. Ecosystem simulation modeling allows predictions to be made for the trajectories of reef ecosystems, given their initial state, interactions between ecosystem components, and a realistic current and future disturbance regime. Together, these technologies have the potential to allow production of coral reef resilience maps. We conclude with a fourth case study that illustrates integration of resilience maps into a multi-objective decision support framework. Implementation of the managing for resilience paradigm is still in its infancy, but the rapidly advancing technologies reviewed here can provide the resilience maps needed for its successful operationalization.

The coastal lagoon ‘Chilika’ along the Bay of Bengal shore (Odisha state, India) support a productive wetland ecosystem that influences the livelihood of local people by providing large scale fishing activity within the lagoon water body, pasturing in the lagoon fringe marshes by rearing livestock and promoting ecotourism in the islands and spits of the lagoon system using nature as magnet of attractions. The lagoon is shore parallel elongated water body enclosed with barrier spits and narrow tidal entrances, and extended in between Mahanadi deltaic distributary channels to the north east and Rishikulya River to the southwest. The average water spread area of Chilika is 1,165 km² during rainy season and gradually it shrinkages to 906 km² during summer months with average depth ranges from 1.70 to 3.70 m.

Physiographically, the lagoon habitats are categorized as (i) Daya-Bhargavi deltaic flats with extensive fresh water wetlands, (ii) brackish water marshes and tidal flats, (iii) islands with marshes and transition vegetation, (iv) islands with mangrove swamps, (v) fresh water weeds of lagoon fringes, (vi) sand spits and dunes, (vii) and lagoon water bodies.

All these habitats are showing significant variations related to geological, sedimentological, hydrological, climatic and ecological factors. Northeastern parts of the lagoon water body have been swallowed by deltaic sedimentation; barrier back shores, islands and other lagoon fringes have shrunk as the result of bordering accretion and encroachment of marshes, weeds and swamps; however, southwestern parts of the lagoon are narrowed, and in some places near-segmented by growth of spits and coalescence of headlands and islands. Opening of tidal inlets have been shifted from one place to other place with time across the enclosed barriers to achieve the balance between water levels of the lagoon and open marine shelf, and as a result of interaction of fresh water from rivers with salt water from the sea during floods and cyclones in the region.

Historically, the habitats of Chilika lagoon provided favorable conditions for maritime trade and commerce, as well as modern fishing related livelihood support system to the local people; but dynamic landscape changes of the lagoon with sedimentation have produced significant effects on human systems by changing salinity regime and eutrophication of enclosed water body. The paper highlights the gradual changes of coastal lagoon systems with variety of habitats influenced by sedimentation, fresh water inputs, local sea levels, tidal mixing and dynamic wetland geomorphology.

Chilika habitats, their geomorphologic changes, ecologic responses, and evolution of the lagoon itself are studied in the present paper using geospatial technology with temporal image data, as well as with available archaeological remains of past maritime activities and existing dating records for better management option and conservation of degraded habitats.

Digital Ocean (DO) is a new research domain of Digital Earth. Because of the spatio-temporal, three-dimensional and intrinsically dynamic nature of ocean data, it is more difficult to make a breakthrough in this domain. In this chapter, the DO technological advances were introduced in detail. Firstly, the technological advances for DO from six aspects. (1) Introduction to DO data sources, which comprise Digital Elevation Model data of the seafloor and coast, in situ observational data, remote sensing data, computational model results and data stored in databases or other medium. (2) The three-dimensional ocean data integration platform. (3) The dynamic tide data visualization. (4) Remote sensing information products integration and sharing. (5) Computational ocean model data integration and service. (6) Spatio-temporal model of marine disasters. Secondly, the DO system initial architecture was introduced, which include the data acquire layer, standard data layer, data service layer, function layer, and application layer, respectively. Thirdly, a case study of DO was introduced, which include the China Digital Ocean Prototype System and the DE in support of an online oceanic educational public service and popularization system named iOcean. At last, the future work relating to DO should be carried out in the seven research areas were introduced as follows. (1) Aiding integrative oceanic scientific research. (2) Constructing regional DO systems. (3) Studying multiple spatio-temporal scales of ocean factors. (4) Studying the relationship between ocean elements at different times. (5) Studying the spatial relationship between different ocean elements or components. (6) Studying the architecture of the DO. (7) Studying the coastal river basin non-point pollution landscape source and assemblage pattern remote sensing parsing.

The study presents new insight into the quantitative role of the world’s third largest discharging river, the Orinoco of South America as modulating coastal water levels in the vicinity of its outflow. The case study is in a semi-enclosed sea, the Gulf of Paria, located in the southern extreme of the Caribbean Sea. The discharge – coastal water level relationship has been investigated and the water levels exhibit a high correlation (R² = 0.92) to the trends in actual discharge. The relationship is non-linear and there is a lower threshold value across the months of the year below which the water levels are characterised by large variability around a mean linear trend showing independence of the Orinoco’s discharge. There is also an upper threshold value where the maximum amplitude of variation is 21.4 cm. The study utilises a vertically integrated 2D numerical modelling suite to execute a series of experiments to ascertain the variation of the coastal water levels from the variation in the river discharge. The other drivers are wind, salinity, oceanic currents and tidal forcing. The results are finally utilised to develop a third order model function to estimate the average monthly river-driven water level in the Gulf of Paria dependent only on the parameter of river discharge.

It is widely recognized that video monitoring systems are excellent tools in coastal morphodynamic studies as they can capture, simultaneously, beach morphological changes and the forcing mechanisms. Over the last years this remote sensing technique has experience huge developments related not only to technology advances but also to the success of numerous applications reported by the scientific community. Since the first steps of video monitoring of the coastal zone, made by the Coastal Imaging Laboratory of Oregon University in the 1980s, several years have passed by enabling the existence of long-term imagery records. The existence of extended high-resolution time-series make possible to broaden typical video application studies from short-term studies to annual (or longer) time scales as morphological inter-annual variability of the coastal systems is still largely unknown. This work summarizes recent developments on the use of video systems in the understanding of yearly to decadal beach morphological changes and describes the application of a video system deployed at Nazaré, Portugal. The system, operational since December 2008, allowed a detailed description of the coastal evolution at a pluriannual timescale. Results, which are in agreement with previous works, indicate that system variability depends not only on the forcing characteristics that occur at different time-scales (storm, seasonal and inter-annual) but also on antecedent morphology. The use of video systems arises as an optimal data acquisition method to capture this variability and thus support the fully understanding of beach morphodynamics at these wide range of spatio-temporal scales.

Estuaries, the interface between terrestrial and coastal waters are an important component of complex and dynamic coastal watersheds. They are usually characterized by abrupt chemical gradients and complex dynamics, which can result in major transformations in the amount, chemical nature and timing of the flux of material along these river–sea transition zones. The ecological functioning of these areas is considered to be of major concern, as estuaries offer the last opportunity to manage water quality problems before they become uncontrollable in the coastal waters.

Numerical models can provide hydrodynamically computed water quality data to study estuary water quality, but they have problems with initializations, boundary conditions, calibration, and validation. Another way is to use remote sensing technology, but they provide only surface observations and there are challenges related to cloud coverage, ground truthing, and variable spatial and temporal resolution.

Although both methods have weaknesses when used together, they can become a powerful tool to study water quality in estuary. This has been demonstrated through recent application of this capability to study water quality problem in Lake Pontchartrain. This study evaluated the use of Landsat 5 TM multispectral imagery to generate spatially distributed water quality data for use in CCHE2D Water Quality model to improve its performance in this estuary to simulate sediment transport, predict algal bloom and monitor salinity after the Bonnet Carré Spillway opening event in 1997. The outcome of this research clearly indicates that the application of remote sensing techniques for estuarine water quality study can be advanced by integrating them with numerical water quality models.

Salt marshes occur throughout the extra-tropical regions of the world, along low energy shores, where a surplus of fine sediment is available, and they have been estimated as some of the most valuable ecosystems on Earth. They exhibit complex topographies primarily modelled by hydrodynamics which, in turn, determine geobiophysical processes and the pattern of occurring communities. This makes accurate salt marsh topography a prerequisite for the understanding of their function and structure. Only recently, have remote-sensing techniques become widely available to obtain high-resolution topographic data in an environment otherwise extremely arduous to access. Still, extraction of bare-earth surface remains difficult and especially problematic in areas of dense vegetation. LiDAR data, although widely in use still isn’t readily available worldwide and requires intensive post-processing and validation.

A detailed digital elevation model (DEM) of the Duplin River (Georgia, Southeastern USA) was constructed with a 1 m² resolution. The model was created by the classification and analysis of a time-series of 7 IR (infrared) aerial photographic mosaics taken at 1 h intervals from low- to high-water during a rising tide. The technique is based on the premise that flooded areas can be objectively recognized through image analysis and that the water surface is horizontal throughout the system, thereby defining a reference level at any given time. We focus on the description of the method, and results from its use in a large intertidal area. We also discuss the advantages of the method and its shortcomings when applied to vegetated intertidal areas, and propose further developments and applications.

Coastal environments are critical ecological systems and offer vital resources and functions to societies worldwide. As a major interface between terrestrial and ocean environments, coastal water bodies (rivers, estuaries, bays and coastal margins) provide key ecological services and are the major conduit and processors of terrestrially derived particulate and dissolved material as they are transported to the ocean. Consequently, coastal environments have been shown to play a major role in global bio-geochemical cycles and provide critical habitat for a host of marine species. Globally, these important environments are under considerable pressure from high population densities, increasing growth rates and are particularly vulnerable from the effects of projected climate change such as sea level rise and increased storm events. Despite their importance, significant gaps remain in our understanding of how these environments will respond to climate change, increasing human population, land use changes, and over exploitation of natural resources. This lack of understanding is due in part to the difficulties in developing effective monitoring and analysis programs using only a single measurement approach that is limited in its spatial and temporal coverage.

We describe an integrated approach based on field measurements, remote sensing and numerical modeling that is being developed to examine the transport of dissolved (colored dissolved organic matter (CDOM), dissolved organic carbon (DOC)) and particulate material (total suspended matter (TSM)) within a complex coastal system, the Albemarle-Pamlico Estuarine System (APES), North Carolina USA. This integrated approach was established to overcome limitations associated with a single measurement and analysis approach. Field measurements and discrete samples are acquired using well-established protocols from small boats, bridges, and from the shore. Remotely sensed data are obtained from several sensors with diverse capabilities including SeaWiFS, MODIS, MERIS, HICO, Landsat and FORMOSAT-2. The numerical model Delft3D is used to simulate freshwater and DOC transport in the estuaries following major rainfall events that lead to high river discharge. Challenges associated with examining the APES using a single vs. an integrated measurement approach along with representative results from a broad suite of measurements are presented. Future advances in technology and refinements in our integrated approach are also considered.

Developments in the coastal area have significant impact on the adjacent shorelines. Mathematical modeling provides a useful tool for predicting such changes in shorelines in advance. Processing and analysis of satellite imageries of coastal area enables us to estimate and monitor the shoreline changes, which is otherwise extremely difficult, time consuming and costly by field surveying. In this paper the shoreline changes obtained by mathematical modelling and by image processing technique are compared by applying these techniques to shoreline adjacent to Ennore region. The study indicated that the cross-shore and longshore impact predicted by mathematical model and satellite information match satisfactorily. Thus the satellite information is useful for calibrating the mathematical model which can be further used for predictive purposes.

Over the last decade, southwest coastal region of Bangladesh has gone through a rapid expansion in shrimp farming. Congenial conditions such as availability of coastal land and water, quality soil and water, successful transfer of hatchery technology and increased export demand led to this rapid growth in shrimp culture sector. Non scientific and unplanned development of shrimp culture has been accompanied by many controversies in the society and in other sectors of agriculture, and the sector has itself been affected adversely by environmental problems. Scientific and sustainable development of shrimp culture essentially needs better site selection. This study identified suitable sites of shrimp culture using GIS and remote sensing technology. Satellite imagery and GIS data- water and soil quality, shrimp culture area, method and production, source and seasonal availability of water, drainage system, water logging, disease outbreak, sanitation facility, road communication, electricity supply, land use pattern, land elevation, hazard frequency, fisheries statistics and population census data etc. were collected in site suitability study. Data were collected through in-situ measurement, laboratory analysis, questionnaire survey and secondary information. Satellite data were used in preparing base map of the study area and visual interpretation of the images was performed using the most important diagnostic characteristics. Decision rules for most important criteria of shrimp culture were followed during site suitability analyses. Study finds most suitable sites of shrimp aquaculture covering 9,309.40 ha area in Shyamnagar upazilla, Satkhira district where moderately and less suitable locations were identified as 19,256.92 and 9,103.90 ha respectively. Paikgacha, one of the shrimp culture dominated upazillas of Khulna got an estimated 9,954.20 ha land as most suitable with 8,919.40 and 6,775.80 ha as moderately and less suitable zone respectively. Study results indicate the existence of 6,403.20, 8,616.70 and 8,867.20 ha area as most suitable, moderately suitable and less suitable for shrimp culture industry in another coastal area-Rampal under Bagerhat district. The study will have utility in formulating shrimp culture policy for sustainable development of this promising sector in the country.

In this work, field data and model outputs were integrated, processed and analyzed in a GIS environment in order to assess the vulnerability to erosion and to produce associated risk maps using a multi-criteria approach. Erosion risk assessment methodology was developed based on morphological, hydrodynamic, and meteorological indicators that were computed using data obtained from a short term monitoring program. It was applied to a stretch on the NW coastal zone of Portugal. Comparing this methodology to previously developed ones, there are three main distinctive aspects to be considered: (i) the coastal stretch was segmented for computation of indexes (susceptibility, exposure and risk), accordingly to specific coastal types (ii) a new set of vulnerability variables is proposed; and (iii) erosion impact indicators computed from detailed building and beaches data that was extracted from aerial photos.