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|Title:||Selected tools and techniques for physical and biological monitoring of aquatic dredged material disposal sites|
|Authors:||Coastal Engineering Research Center (U.S.)|
Dredging Operations Technical Support Program (U.S.)
Fredette, Thomas J., 1955-
Nelson, David A.
Adair, Jeffery A.
Sotler, Virginia A.
Clausner, James E.
Hands, Edward B.
Anders, Fred J.
Aquatic dredged material
Remote sensing tools
|Publisher:||Environmental Laboratory (U.S.)|
Engineer Research and Development Center (U.S.)
Abstract: Monitoring of aquatic dredged material disposal sites may require a variety of physical and biological tools and techniques. Chemical monitoring tools and techniques are not discussed in this report since this document does not address chemically unsuitable material. In the tiered approach discussed in the companion report ("Guidelines for Physical and Biological Monitoring of Aquatic Dredged Material Disposal Sites"), the lower level tiers may examine primarily physical changes at a site. Changes in physical environment, such as mounding, can result in a navigation hazard or lead to changes in the biological community (e.g., burial), which necessitates biological monitoring. Design of a monitoring program must consider what equipment to use and at what spatial and temporal frequency to sample. These factors will be determined by the level of information required for the questions being addressed, given present technical, monetary, regulatory, and political considerations. Physical monitoring tools: Physical monitoring tools can be broadly classified into several groups. Navigation and positioning equipment, though not actually monitoring tools, are primary among these. The effectiveness of all physical and biological sampling depends upon knowing the location of a sample relative to the disposal site. A variety of equipment types are available for locating a sample. Generally, more precise locationing requires more complex and expensive systems. Equipmsnt that measures bathymetry and ocean bottom configuration with acoustic energy is a second group. A third group of physical instruments consists of those that directly sample sediment. These range from grab samplers, which one person can operate to retrieve a small surface sample, to large vibracores that return a core (up to 40 ft (12 m) long) through a disposal site. A fourth group of tools for physical monitoring includes those instruments that return data on site conditions remotely through the use of photography. These instruments, such as the sediment-profiling camera or video cameras attached to remotely operated underwater vehicles, have had success in helping to delineate outer fringes of disposal material, where necessary within a site. In situ measurements of engineering properties of mounds, such as density, sediment size, pore pressure, settlement rates, and shear strength, are possible with a fifth group of tools. Waves and current meters form the last group of tools that may be useful in physical monitoring. They are used to measure the driving forces for sediment transport. Biological monitoring tools: Fish and shellfish are generally the animals of the greatest socioeconomic importance to individuals and agencies. However, obtaining quantitative information about a given species or assemblage presents more of a problem with mobile organisms such as fish and shellfish. Most sampling devices are selective in terms of size and, often, species, causing a bias in the resulting estimates of density, species diversity, or biomass. Considerable difficulty is often faced in obtaining replicate data, due to the variability in dispersion of individuals and their mobility. This results in great variability in both time and space. Sampling of nektonic organisms (fishes, shrimps, and crabs) is most commonly accomplished through the use of nets or traps of various types. The choice of sampling device(s) for monitoring depends on the type(s) of organism(s) of interest. Benthic infauna (particularly macrobenthos) and submergent vegetation are regarded as good indicators of environmental quality because of their sedentary nature and thus their susceptibility to physical and chemical alterations. In addition, they can be sampled more quantitatively and efficiently. Grab samplers and box corers are the tools of choice for quantitative sampling of sessile epifauna and infauna (to the depth excavated by the sampler).
|Rights:||Approved for public release; distribution is unlimited.|
|Appears in Collections:||Technical Report|