When determining the potential of a coastal area for aquaculture or other development, knowledge of the sediment dynamics of the site is required. Sediment grain size is the most basic of classification criteria that can be used to determine the suitability of both an individual site and the receiving environment for development. It can also be used as an environmental monitoring tool.

INSSECT is used to measure floc fractions in suspension.

Bottom sediments preserve within their grain size distributions a record of the physical transport processes responsible for their formation. Land and shore erosion produces sediment grain size distributions in which the amount of material in each size class varies constantly, from sub-micron sized clays to coarse sands and gravels. These straight-line size distributions are modified as they are transported by water. The maximum grain size of a sediment defines the maximum turbulent energy to which the sediment is exposed (Kranck et al. 1996 a, b). The degree of sorting indicates how frequently the material is resuspended, the extreme case of which is beach sands which have very well sorted, narrow, size distributions the modal diameters of which precisely reflect wave energy (Kranck et al., 1996 b). In most estuaries there are considerable amounts of naturally occurring fine particulate material delivered to the water body from river run off and shore erosion. These clays and fine silts are unable to settle through the water column unless they flocculate with other particles to form large, fast settling aggregates or marine snow. Studies have shown that floc size, and hence settling velocity of the fine particulate material, is controlled by turbulence and particle composition (Milligan and Hill, 1998) and that aggregation rate is also dependent on concentration (Kranck, 1980, Jackson, 1994, Hill, 1996). Kranck (1980) showed that flocs deliver material to the bottom in the same proportions as that in which they are found in the suspension. Because it is derived from the straight-line size distributions created by erosion, the slope of the size distribution of sediment deposited as flocs is the same as that of the material in suspension. The maximum size of the floc derived portion of the sediment, the floc limit, is controlled by the balance between aggregation which increases the settling velocity of the fine material and the settling rate of the largest single grains still in suspension (Milligan and Loring, 1997).

	SLOWCORER is used to take sediment cores from the ocean floor.

Precise grain size analysis of the disaggregated inorganic material in a sediment, possible only with electro-resistance particle size analyzers such as the Coulter Multisizer, allows it to be broken down into the three major components from which it was formed: material deposited as flocs, material deposited as single grains from suspension and material carried under higher energy conditions (Kranck, 1993, Kranck et al., 1996a,b). The method determines not only if a site is depositional or erosional but also the amount of material it receives in a flocculated form and the frequency of erosional events. In addition, grain size analysis of the bottom sediments within an estuary will define the sediment dynamics of the region and identify areas likely to be most severely impacted by deposition of flocculated material and its associated contaminants (Milligan and Loring, 1997).

DFC (digital floc camera) is used to measure sizes of floc in suspension.

Grain size analysis can also be used to evaluate changes in sedimentation as a result of anthropogenic influences. Changes to turbulence levels, particle concentration or particle stickiness will be reflected by the bottom sediments. The increased fine particulate load, and the possible increase in the amount of biological "glue" in the form of polysaccharides which results from aquaculture can increase the rate of flocculation in an inlet and change the deposition rate and distribution of fine sediments (Milligan and Loring, 1997). By examining the particle size distribution of sediments in regions of aquaculture it is possible to determine zones of fine particle deposition and assess changes in particle dynamics for an area.