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| Environmental Technologies & Engineering
The goal of this research priority is to develop interactive observatories, sensors, autonomous samplers, and models for real-time, continuous, cost-effective monitoring, forecasting, and assessment.The following eight projects have been funded by Delaware Sea Grant for the 2005–2007 period:
For additional information, please also see our latest annual report. Prediction
of Wind-Induced Subtidal Sea Level and Current Variations
in the
Delaware Estuary Based on a Combined Database from
Three Coastal/Estuarine
Observing Systems (PORTS, DBOS, and DEOS)
Sea-level height and currents in estuarine and coastal waters vary in response to a number of mechanisms — among the strongest are tidal fluctuations and wind. Although the regularity of tides allows their effect to be predicted with some measure of confidence, predictability becomes far less certain when winds enter the equation. According to UD oceanographers Kuo-Chuin Wong and Mohsen Badiey, wind events that may last for several days in major estuaries, such as the Delaware Bay, may elevate or depress sea-surface heights by more than 3 feet (1 meter). “The elevated sea level may heighten coastal flooding concerns, and the depressed sea level affects navigational safety,” says Badiey. “Unfortunately, the inherent variability in wind has made it difficult to predict these effects with any accuracy.” With the emergence of coastal and estuarine observing systems in recent years, it is now possible to make continuous measurements of wind speed and direction — a critical component in understanding the effect that wind has on sea level and currents. Continuous measurements consist of six 10-minute average values of wind speed and direction reported each hour. In this Sea Grant project, Wong and Badiey will combine extensive observations of sea level, current, and wind that have been collected from three coastal observing systems in the Delaware Bay — Delaware River and Bay PORTS (Physical Oceanography Real Time System), DBOS (Delaware Bay Observing System), and DEOS (Delaware Environmental Observing System). Delaware River and Bay PORTS, installed in 2002, formerly maintained 11 tide gauges spanning the length of the Delaware estuary. In addition, the system measured wind speed and direction as well as atmospheric pressure at eight of these locations. PORTS also maintained four current stations — one near the mouth of the bay and three in the upper estuary. However, only the tide gauges at Lewes, Cape May, Reedy Point, and Philadelphia are currently maintained. DBOS is a lighthouse-based observing system established by Badiey and Wong in 2002 in a previous Sea Grant project. Measurements of wind speed and direction and current velocity and direction as well as other measurements, including air and water temperature, are obtained from the Fourteen Foot Bank Lighthouse. The third observing system, DEOS, is used to monitor environmental conditions in the state of Delaware. Meteorological sensors have been installed throughout the Delmarva region, including two stations along the shoreline of the lower bay and another two on Delaware’s Atlantic shoreline. The combined database from these three observing systems will provide extensive information about the wind field over the bay. The scientists will use this information, along with wind measurements from a buoy located some 100 feet (30 km) off the mouth of Delaware Bay, to describe the variation in the wind field over the length of the bay as well as tidal and subtidal characteristics and current fluctuations in the bay. “Subtidal variabilities in estuaries, especially those that occur over time scales of several days, are largely induced by wind through a combination of remote and local effects,” says Wong. “In the case of the Delaware Bay, remote winds can produce coastal sea-level fluctuations at the Lewes-Cape May transect, which then propagate into the bay up to Trenton, New Jersey. Badiey adds that local winds, which blow across the surface of the water, also produce significant fluctuations in the bay that are very different from those of remote winds. Once the wind field and the sea levels and current fluctuations have been characterized, Wong and Badiey will establish the relationship between wind and sea level and current variability at different sites along the estuary. This relationship will be used to develop a model that will allow for nowcast and short-term (up to 12 hours in the future) forecasts of the wind-driven sea level and current based on wind observations. “The accurate prediction of wind-forced sea level will significantly benefit residents and environmental managers who are concerned about coastal flooding under strong wind events,” says Badiey. “In addition, accurate sea level and current prediction will benefit river pilots and mariners who navigate the Delaware Bay. Wong adds that accurate predictions of wind-forced currents will improve the ability to conduct search-and-rescue operations and to respond to events such as oil spills.
Application of Decision-Support Model to Reduce the Risk of Introduction of Aquatic Organisms by Maritime Commerce: Chesapeake Bay and Miami Regions
Ballast has been used for centuries to help stabilize ships and to increase their maneuverability. Originally, ballast was solid material such as stones, gravels, and iron that was stowed below deck. During the early twentieth century, however, bigger ships started to be built. These bigger ships required more ballast, and a shift was made from solid material to fresh or salt water. Water not only was faster to load and unload in port, but also could be easily taken on board or discharged during a voyage. According to UD marine policy experts James Corbett and Jeremy Firestone, the shift from solid to water ballast as well as economic globalization, which increased the number, size, and speed of ships engaged in international commerce, has greatly increased the potential for humans to transfer invasive species from one aquatic environment to another. “Scientists estimate that approximately 3,000 species are transported in the ballast water of ships or on their hull each day,” says Corbett. “Discharging ballast water can introduce these potentially invasive species into ports, causing ecological, socioeconomic, and human health consequences.” In this Sea Grant project, Corbett and Firestone will develop a decision-support model that will help its users choose between various alternatives that can be used to reduce the introduction of potentially invasive species from ballast water, maximize participation by vessels according to their relative risk of introducing organisms, minimize total cost to both the public and private sector, reduce the time frame for achieving reductions, and protect sensitive ecosystems. The scientists will look at alternatives such as treating ballast water through a variety of technological methods as well as establishing policies to regulate the amount of ballast water that can be discharged in an aquatic environment. The model will provide support for a particular decision by illustrating the effectiveness and cost of different combinations of treatment methods and policy approaches. The scientists will collect data on such characteristics as the size of the ballast water tank in a given vessel, the length of the voyage, the total volume of ballast water discharged or exchanged at sea, the concentration of organisms in ballast water, and the temperature and salinity of the water at a port. In addition, information on treatment options — including their effectiveness and cost — and policy approaches will be collected. The resulting model will enable users to change any of these parameters to see which combination makes the most sense — both monetarily and environmentally. “The resulting model will be used to estimate the risk-reduction potential of emerging technologies, determine their cost-effectiveness, and evaluate the amount of uncertainty that is involved in various decisions,” says Firestone. “In addition, it identifies least-cost technology strategies to achieve various levels of risk-reduction. These targets can be applied individually to vessels or regionally to port traffic.” Corbett adds that the model also can be used to rank technology-policy schemes by risk mitigation, cost impacts to ship operation or cargo freight rates, and policy design. This project is funded by Sea Grant in partnership with the University of Maryland Center for Environmental Science and Rochester Institute of Technology.
Advancing Remote Sensing Techniques for Observing the Coastal Ocean
Ocean observing systems are fast becoming the “eyes and ears” for scientists who study the ocean. Several pilot programs have demonstrated that these systems are ideally suited for studying coastal and ocean processes because they have been designed to systematically collect data over relatively large regions for extended periods of time. In addition, Yan will develop and advance techniques for the processing and analyzing of remote-sensing data. An information database on the Internet will be developed to make the results and products of the proposed project as well as past and future research data accessible to a wide variety of users.
Sediment Transport in the Delaware Estuary on Tidal Seasonal Time Scales
In the Delaware Estuary, fine-grained sediments are at the heart of complex management issues ranging from maintenance dredging to toxic contamination. An ability to predict patterns and rates of sediment deposition and erosion in the estuary is much needed—the first logical step toward this capacity is to understand the fundamental underpinnings of the transport regime. Building on insight gained from previous Sea Grant–funded research, marine geologist Christopher Sommerfield and oceanographer Kuo-Chuin Wong will examine suspended-sediment transport in the estuary on multiple timescale, focusing on the turbidity maximum zone, a mobile repository of particulate matter. Using a combination of in-situ time series and shipboard observations, the scientists will investigate mechanisms that moderate tidal and residual sediment fluxes during high- and low-riverflow conditions. The dynamical insight that stems from this study has potential to provide an indispensable foundation for numerical models of material transport in the estuarine system. This study is being conducted in cooperation with the Delaware River Basin Commission.
Real-Time Surface Wave Measurement and Modeling in Delaware Bay
Ocean acoustics — the use of underwater sound waves to learn more about the sea — represents a promising method for determining the physical properties of coastal waters, such as temperature and salinity. However, sea-surface turbulence, or “roughness,” generated by wind, waves, tides, and currents, can have a major effect on how sound travels underwater. In this Sea Grant project, UD coastal engineer James Kirby is working to provide information on sea-surface turbulence in the Delaware Bay that can be integrated into a related Sea Grant project — a laboratory acoustics modeling study — conducted by UD colleagues Mohsen Badiey and Kuo-Chuin Wong. At present, scientists do not have the ability to correlate the acoustic scattering process due to sea-surface roughness with any parameter beyond wind speed and direction. This project seeks to enable scientists to correlate the movement of sound underwater with surface waves and other water circulation processes. Kirby will be using a wind-wave model called SWAN to obtain estimates of what the local surface wave conditions in Delaware Bay would have been when Badiey conducted a short-term acoustics experiment in the bay a few years ago. This information will then be incorporated into Badiey's laboratory acoustics model. According to the researchers, the coupled circulation and wind-wave model developed in this study could serve as the basis for the subsequent development of an operational or predictive model for hydrodynamic conditions in the bay with applications in tracking pollutant and sediment transport, in oil spill management, and in dredging operations management. The model also should provide a useful demonstration tool for educational programs about the Delaware Bay.
Morphological Modeling of Intertidal Mudflats
Intertidal mudflats are formed in sheltered coastal environments when sediments consisting of silts and clays with a high organic content are deposited by tides or rivers. These mudflats typically have gentle slopes and are covered during high tides and uncovered at low tides. Mudflats are important habitats for marine invertebrates such as marine worms and clams, which, in turn, provide food for large populations of shorebirds and fish. In addition, they help protect the shoreline from erosion and are important to the creation and restoration of salt marshes — another critical habitat found in the intertidal zone. According to coastal engineer Nobuhisa Kobayashi, director of UD’s Center for Applied Coastal Research, the morphology of mudflats depends on a number of physical processes including tidal range and currents, average sea level, waves, river discharge, and storm action. Although the actual influence of these various processes is poorly understood, the gentle slope of intertidal mudflats makes them particularly susceptible to flooding as sea level continues to rise. In this Sea Grant project, Kobayashi is developing a numerical model to predict the morphological changes in tidal mudflats due to variations in sea level, tides, and waves. The model will be calibrated and verified with data collected in an ongoing field experiment in Japan, which was initiated by Fumihiko Yamada of Kumamoto University in Japan and funded by Japan’s Ministry of Education, Science and Culture. This data includes information on the tidal water level, tidal range, sediment composition, and waves. “The model will provide an understanding of how sediment is transported in mudflats under the combined action of tides and wind-induced waves,” says Kobayashi. “It also will provide the information needed to plan coastal management projects such as wetland restoration and creation.” Kobayashi adds that the model can be applied to predict the morphological changes in the intertidal mudflats under possible ranges of future sea-level rise.
Voltammetric Microelectrodes for the Determination of
Biogeochemically Relevant Species
in Sediments and Waters
Continuous monitoring of various trace metals and chemical compounds in coastal waters and sediments can provide critical information on the environmental effects of these substances as well as indicate the overall health of the ecosystem. Until recently, monitoring of these substances involved collecting water and sediment samples and analyzing them in the lab — a process that took a significant amount of time. This changed when marine chemist George Luther, with previous funding from Sea Grant and the National Science Foundation, pioneered the development of a gold-tipped microelectrode that can be used in both water and sediment to rapidly and simultaneously measure a host of trace metals and chemical compounds. The microelectrode has now been adapted for use in a chemical analyzer system, which can take measurements from four different electrodes. These electrodes can be mounted at different depths or different locations. In this continuing Sea Grant project, Luther and his research team will use the chemical analyzer system to measure the water quality in several “deep holes” located in the Torquay Canal and Bald Eagle Creek area of Rehoboth Bay. Summer storms cause the water in these holes to overturn, bringing poisonous hydrogen sulfide that forms in the stagnant bottom waters to the surface. One analyzer will be used from a small boat to obtain profiles of the water column in real time. Measurements of various chemical compounds including oxygen, sulfide, and soluble iron sulfide will be taken on a biweekly basis from late spring to early fall. Water samples also will be collected to calibrate and verify the results obtained from the analyzer. “This work will provide information on how hydrogen sulfide, produced in bottom sediments, is released into the water column and how this compound affects ecosystem health,” says Luther. The information also will be used to determine the efficacy of several solar-powered water circulators that have been placed in the deep holes. Luther and his team also will coordinate their efforts with research being conducted by UD colleagues David Hutchins and Mark Warner, who are studying the organisms responsible for algal blooms, in a related Sea Grant project. Coupling of the chemical data with the biological data will provide a greater understanding of the life cycle of these organisms. In addition, another chemical analyzer will be moored to a homeowner’s dock in Rehoboth Bay for unattended operation. This analyzer will continuously monitor the level of oxygen and hydrogen sulfide and in real time. According to Luther, mooring-based systems can be effective in measuring suboxic or anoxic conditions (conditions of low or depleted oxygen levels, respectively) that affect commercial and recreational fisheries on a seasonal basis. “There are several major U.S. ecosystems that undergo seasonal anoxia, such as the Chesapeake Bay and the Gulf of Mexico, that could be studied with moored analyzers,” says Luther. “A device, such as this, that can be kept at station with continuous as well as unattended collection and retrieval of data is essential for understanding how chemistry affects complex biological processes.” A second objective of this Sea Grant project is to determine the feasibility of using the electrode to conduct long-term chemical monitoring of coastal waters. To accomplish this goal, another analyzer will be integrated into the Delaware Bay Observing System (DBOS), which currently monitors physical and meteorological parameters such as wind speed and sea level, from a lighthouse in the lower Delaware Bay. The four electrodes in the analyzer will be mounted at different depths and will measure oxygen and perhaps sulfide in bottom waters at intervals of 15 minutes or less from DBOS. The data will be directly transmitted to a lab computer for analysis and will be incorporated into biogeochemistry models developed by Dominic M. Di Toro, Edward C. Davis Professor in the University of Delaware Department of Civil and Environmental Engineering. “There is a critical need to have robust chemical sensors for ocean observatories,” says Luther. “These sensors must be integrated with other physical, geological, and biological sensors so that we can better understand ocean and coastal scale processes.”
Field Observations and Predictions of Rip Currents
Rip currents are coastal hazards that pose serious threats to life and safety. Reports from the U.S. Lifesaving Association state that 80% of all surf rescues in the United States are related to rip currents. In some years, drowning deaths due to rip currents have exceeded the deaths due to hurricanes and tornados; and they can be responsible for up to a quarter of all natural hazard deaths in the United States. What makes rip currents so dangerous? These currents are extremely strong and can pull even the strongest swimmer of their feet. Characterized by fast-moving water that flows out to sea, rip currents can form along any beach with breaking waves. They typically extend from near the shoreline, through the surf, and out past the line of breaking waves. According to coastal engineer James Kirby, Edward C. Davis Professor of Civil and Environmental Engineering, there are a large number of possible reasons why rip currents occur, including waves that interact with the sea bottom or structures such as groins or jetties. However, the mechanisms that cause rip currents are not well understood, making them difficult to predict and leads to false alarms. Kirby adds that these false alarms can teach swimmers to ignore the rip current warnings. They also can have a large economic impact on the coastal communities if they keep bathers from the beach. "There is a clear need to develop a simple tool for the prediction of rip currents that can be used by lifeguards and the National Weather Service," says Kirby. "This prediction tool must be based on a knowledge of the mechanisms for rip currents and their likelihood of occurrence." In this Sea Grant project, Kirby will integrate field data on rip currents and their mechanism of generation with numerical modeling techniques to develop a theory-based rip current prediction scheme. This will not only lead to an improved prediction capability for conditions leading to the formation of rip currents, but also reduce the number of false alarms. Video cameras will be installed on Bethany Beach, Delaware, to monitor conditions in the surf zone and changes in the seabed. The footage will be archived and made available on a Web site hosted by the Center for Applied Coastal Research at the University of Delaware. In addition, it will be correlated with visual observations of rip conditions by lifeguards on Bethany Beach being conducted in cooperation with Wendy Carey, coastal hazards specialist with the Delaware Sea Grant, to help identify which mechanism is likely to be occurring. In addition, Kirby will analyze existing wave data from Ocean City, Maryland, for any occurrences of a rip current. Each occurrence will be correlated with existing tidal and metrological data, as well as with the observational data from the video cameras and the lifeguards, to determine the most likely mechanism that generated each rip current. Once the most likely mechanisms are identified, numerical models that simulate the currents and wave actions in the near-shore beach environment will be used to determine the most important parameters involved in the generation of these rip currents. "This effort will lead to a simple model that will predict rip currents based upon meteorological conditions," says Kirby. "For example, if intersecting waves or wave groups are found to be an important mechanism in generating rip currents in Bethany Beach, then wave data can be used to detect critical conditions. This type of predictive model could easily be put on a Web page and used as an accurate, but early warning system." This project is a collaborative effort with Robert A. Dalrymple at Johns Hopkins University in Baltimore, Maryland, who is establishing a similar beach monitoring system in Ocean City, Maryland.
Supply of Larvae to Estuarine Nursery Habitat:
From an economic standpoint, the blue crab is the most valuable shellfish in the Mid-Atlantic region, so when the crab harvest takes a downturn, local residents want to know why. Recent field surveys indicate that blue crabs may be overfished in both estuaries, which has resulted in stringent and controversial catch limits on the fishery. However, natural forces — wind and rainfall — also can impact the crab population, according to Sea Grant research conducted by UD marine biologist Charles Epifanio and his colleagues. In previous Sea Grant studies in Delaware Bay, Epifanio and colleague Richard Garvine, a physical oceanographer at the UD College of Marine and Earth Studies, determined that once the tiny, larval crabs hatch in July and August, they get swept out of the bay and onto the continental shelf by the Delaware Coastal Current. Summer winds then push the crabs home, back into their bay nursery grounds. "If river flow is at a minimum due to drought, wind has a greater effect in shuttling the crabs back into the bay," Epifanio says. "Thus, the supply of larval crabs may be highest in drought years."
In the current Sea Grant research project, which includes physical oceanographer Charles Tilburg at the University of Georgia on the research team, the scientists are testing their hypothesis using satellites to track the crab patches, coupled with intensive sampling operations at various locations in the bay. This spatial data will help them refine a unique mathematical model that considers the genesis, maintenance, and transport of patches of blue crab larvae in time and space. The novel tool should aid state regulators in predicting the annual population of blue crabs and determining optimum strategies for managing the blue crab fishery.
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   Copyright © University of Delaware College of Marine & Earth Studies and the Delaware Sea Grant College Program |
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