Bathymetry Difference

Figure 8c. 1996-2000

Topography observed in the 2000 subtracted from 1996. Positive features (red shades) indicate shallower water in 2000 compared to 1996; negative features (blue shades) indicate deepening of the water. Local changes in depth are observed where dredged material was placed between the 1996 and 2000 surveys. More accurate information on the amount of material placed at each site and the water content of the sediment on the seafloor is needed to determine if any of the material placed on the sea floor in the HARS has been eroded and transported from the site. However, the data suggest little net accumulation in Area 3, compared to the other areas that received similar amounts of material (Figure 6, Table 1 [PDF]). The material placed in Area 3 was mud and silt which spreads easily during placement and may be easily eroded. Some loss of material is more likely at this shallow site than from deeper areas. The feature centered near 40 ° 22.97' N., 73° 50' W. results from a small offset in an apparent position of the sharp mound that rises to within 12 m of the surface. The north-south stripes, running parallel to the survey tracklines, are artifacts of environmental conditions during data collection.