Using existing scientific capacity to set targets for ecosystem-based management: A Puget Sound case study

Human actions have altered the structure and function of coastal ecosystems worldwide. In many locations, the overall portfolio of goods, cultural amenities, and supporting services provided by the marine environment has deteriorated. Ecosystem-based management (EBM) offers significant promise for addressing these issues because it is a comprehensive and integrated approach designed to reconcile conflicts and trade-offs among users of marine resources. A key step in the implementation of EBM is the establishment of target reference levels, or desired states, for indicators that reflect the status of the ecosystem. This paper reviews five approaches, borrowed from a variety of disciplines, to establish target reference levels for EBM. The approaches include the use of existing reference levels, reference directions, and reference levels based on nonlinear functional relationships, baselines, or social norms. Each approach is particularly suitable for EBM because it can be used alone or in combination with others to contextualize status for a diverse suite of ecosystem goals influenced by a wide variety of human activities. Perhaps most importantly, these approaches offer a prospectus for moving forward with EBM by using readily available information, motivating existing scientific capacity, and addressing trade-offs implicit to the setting of targets. This last point is articulated via examples of how each type of reference level might be applied in Puget Sound, WA, USA, where the efforts of scientists, managers, and policy makers have aligned recently in the interest of EBM implementation.     

Measured and modeled wave overtopping on a natural beach

The rate of wave overtopping of a barrier beach is measured and modeled. Unique rate of wave overtopping field data are obtained from the measure of the Carmel River, California, lagoon filling during a time when the lagoon is closed-off with no river inflow. Volume changes are based on measured lagoon height changes applied to a measured hypsometric curve. Wave heights and periods are obtained from directional wave spectra data in 15 m fronting the beach. Beach morphology was measured by GPS walking surveys. Three empirical overtopping models by Van der Meer and Janssen (1995), Hedges and Reis (1998) and Pullen et al. (2007) with differing parameterizations on wave height, period and beach slope and calibrated using extensive laboratory data obtained over plane, impermeable beaches are applied in a quasi-2D manner and compared with the field observations. Three overtopping events are considered when morphology data were available less than 2 weeks prior to the event. The models are tuned to fit the data using a reduction factor to account for beach permeability, berm characteristics, non-normal wave incidence and surface roughness influence. In addition, the run-up model by Stockdon et al. (2006) based on field data is examined and found to underestimate run-up as the calculated values were too small to predict any of the observed overtopping. The three overtopping models performed similarly well with values of 0.72–0.87 for the two narrow-banded wave cases, with an average reduction factor of 0.78. The European model (Pullen et. al., 2007) performed best overall and in particular for the case of the broad-banded, double peaked wave spectrum.     

Appraisal of storm beach buffer width for cyclonic waves

The loss of beach sand from berm and dune due to high waves and surge is a universal phenomenon associated with sporadic storm activities. To protect the development in a coastal hazard zone, hard structures or coastal setback have been established in many countries around the world. In this paper, the requirement of a storm beach buffer, being a lesser extent landward comparing with the coastal setback to ensure the safety of infrastructures, is numerically assessed using the SBEACH model for three categories of wave conditions in terms of storm return period, median sand grain size, berm width, and design water level. Two of the key outputs from the numerical calculations, berm retreat and bar formation offshore, are then analysed, as well as beach profile change. After having performed a series of numerical studies on selected large wave tank (LWT) test results with monochromatic waves using SBEACH, we may conclude that: (1) Berm erosion increases and submerged bar develops further offshore as the storm return period increases for beach with a specific sand grain size, or as the sand grain reduces on a beach under the action of identical wave condition; (2) Higher storm waves yield a large bar to form quicker and subsequently cause wave breaking on the bar crest, which can reduce the wave energy and limit the extent of the eroding berm; (3) A larger buffer width is required for a beach comprising small sand grain, in order to effectively absorb storm wave energy; and (4) Empirical relationships can be tentatively proposed to estimate the storm beach buffer width, from the input of wave conditions and sediment grain size. These results would benefit a beach nourishment project for shore protection or design of a recreational beach.     

The eastern slope of the southern Adriatic basin: a case study of submarine landslide characterization and tsunamigenic potential assessment

Marine Geophysical Research - The southern Adriatic basin is the current foredeep of the Albanide fold-and-thrust belt that runs along the eastern boundary of the Adriatic basin and partly owes its...     

Modelling tidal current turbine wakes using a coupled RANS-BEMT approach as a tool for analysing power capture of arrays of turbines

An improved method is developed to couple an inner domain solution of the blade element momentum theory with an outer domain solution of the Reynolds averaged Navier Stokes equations for evaluating performance of tidal current turbines. A mesh sensitivity study shows that a mesh of at least 6 M cells with at least 40% of these within the turbine wake is required to ensure satisfactory convergence of the velocity deficit. In addition to the usually applied axial momentum source terms, angular momentum and turbulence intensity source terms are shown to be required to model the near wake evolution. Three different lateral turbine spacing of 2, 4 and 6 turbine diameters are used to demonstrate the influence of the effective channel blockage on the velocity distribution in the turbine bypass region, the rate of spread of the wake and the recovery of velocity distribution. A final study shows that for a fixed number of turbines minimising the lateral spacing within each row, with a small number of staggered rows spaced as longitudinally as far apart as practical, is the most effective strategy for energy capture.     

Impact of Ocean Mean Dynamic Topography on Satellite Data Assimilation

The response of an eddy-permitting ocean model to changes imposed by the use of different mean dynamic topographies (MDT) is analyzed in a multivariate assimilation context, allowing the evaluation of this impact, not only on the surface circulation, but also on the interior ocean representation. The assimilation scheme is a reduced-order sequential Kalman filter (SEEK). In a first set of experiments, high resolution sea surface temperature, along-track sea surface height and sea surface salinity from climatology are assimilated into a 1/3° resolution North and Tropical Atlantic version of the HYCOM model. In a second experiment, in situ profile data are assimilated in addition to the surface measurements.

The first set of experiments illustrates that important differences in the representation of the horizontal model circulation pattern are related to differences in the MDT used. The objective of assimilation is to improve the representation of the 3D ocean state. However, the imperfect representation of the mean dynamic topography appears to be an important limiting factor with regard to the degree of realism obtained in the simulated flow.

Vertical temperature and salinity profiles are key observations to drive a general circulation ocean model toward a more realistic state. The second set of experiments shows that assimilating them in addition to sea surface measurements is a far from trivial exercise. A specific difficulty is due to inconsistencies between the dynamic topography diagnosed from in situ observations and that diagnosed from sea surface height. These two fields obtained from different data sources do not contain exactly the same information. In order to overcome this difficulty, a strategy is proposed and validated.     

The state‐of‐the‐art in marine navigation

Tide gauges distributed all over the world provide valuable information for monitoring mean sea level changes. The statistical models used in estimating sea level change from the tide gauge data assume implicitly that the random model components are stationary in variance. We show that for a large number of global tide gauge data this is not the case for the seasonal part using a variate-differencing algorithm. This finding is important for assessing the reliability of the present estimates of mean sea level changes because nonstationarity of the data may have marked impact on the sea level rate estimates, especially, for the data from short records.     

Quantification of Spatial and Thematic Uncertainty in the Application of Underwater Video for Benthic Habitat Mapping

This study presents an analysis of the application of underwater video data collected for training and validating benthic habitat distribution models. Specifically, we quantify the two major sources of error pertaining to collection of this type of reference data. A theoretical spatial error budget is developed for a positioning system used to co-register video frames to their corresponding locations at the seafloor. Second, we compare interpretation variability among trained operators assessing the same video frames between times over three hierarchical levels of a benthic classification scheme. Propagated error in the positioning system described was found to be highly correlated with depth of operation and varies from 1.5m near the surface to 5.7m in 100m of water. In order of decreasing classification hierarchy, mean overall observer agreement was found to be 98% (range 6%), 82% (range 12%) and 75% (range 17%) for the 2, 4, and 6 class levels of the scheme, respectively. Patterns in between-observer variation are related to the level of detail imposed by each hierarchical level of the classification scheme, the feature of interest, and to the amount of observer experience.     

Ferromanganese Nodules and Crusts from the Christmas Island Region,Indian Ocean

A sampling expedition has shown that largely hydrogenetic marine ferromanganese deposits occur in the Christmas Island region south of Java (~10°S), as small nodules on seamount slopes and abyssal plains (red clay), and as thick crusts on volcanic ridges and seamounts. Vernadite is dominant, with birnessite, jacobsite and todorokite common. Nodules were recovered in 25% of free-fall grab stations in water 4600-5900 m deep, and are not abundant where present. The nodules average 9.6% Fe, 19.7% Mn, 0.51% Ni, 0.49% Cu, and 0.12% Co. Crusts are common in water 1450-3700 m deep, with average deposition rates of 1-1.5 mm / m.y. The crusts average 13.9% Fe, 16.2% Mn, 0.35% Ni, 0.11% Cu, and 0.44% Co. Cobalt grades are higher (~0.8%) in shallower water ( < 2500 m), so future exploration should concentrate on depths of 500-1500 m near the oxygen minimum zone.     

Cement Deep Soil Mixing (CDSM) for Solidification of Soft Estuarine Sediments

A preliminary study was conducted to determine the potential for cement deep soil mixing (CDSM) technology as a method for in-situ solidification of contaminated river and estuarine sediments. The study was conducted in Newark Bay, near the mouth of the Passaic River, New Jersey. The primary objective of the study was to evaluate the viability of CDSM for the in-situ S/S with a focus on: 1) determining the correct mix of the cement slurry, which provides rapid stabilization of the sediment matrix, 2) potential resuspension of solids during CSDM operations, 3) the effects of high organic content on the solidification process, and 4) the feasibility of using conventional dredging/extraction methods once the sediments have been stabilized and allowed to cure. The results of the study show CDSM slurry mixtures, as low as 7% in cement content, result in significant solidification and strength gain of in-situ sediments under ambient conditions. In sediments with very high organic contents (> 20%), the slurry mix would need to be adjusted to account for retardation effects of organics on cement hydration. Sediment resuspension during application was shown to be minimal at a distance of as little as 75 feet from the mixing head. Strength gains were considerable, effectively consolidating the sediment particles in a secure matrix, but not so high as to preclude extraction of solidified sediments with conventional dredging equipment. Dredged solidified sediment exhibited characteristics of a stiff glacial clay, and as such was easier to handle and transport than untreated dredged sediments. This technique has high potential to be used as an interim remedial measure prior to either extraction and decontamination/disposal or proper capping.