Figure G10. Mean value with error limits for frequency of vertical erosion from extratropical storms for 8-ft mound located at 83-ft depth, crest depth of 75 ft

Figure G10. Mean value with error limits for frequency of vertical erosion from extratropical storms for

8-ft mound located at 83-ft depth, crest depth of 75 ft

Therefore, estimates of potential erosion of a disposal mound in the

New York Bight require an analysis of both (a) episodic event erosion resulting

from tropical and extratropical storms and (b) cumulative erosion. For the Mud

Dump site, cumulative erosion would be considered to be due only to average

intensity extratropical events. Tropical events are not considered in the average

yearly erosion rate because tropical events impact the Bight at a return period of

approximately 6.5 years. At more southerly east coast sites and Gulf coast sites,

tropical storms may need to be considered for the yearly average erosion

Cumulative erosion. As noted above, cumulative erosion is the vertical

erosion expected to occur over intervals of 5 to 20 years due to a normal storm

activity, i.e., moderate storms that occur regularly. Because cumulative erosion

over periods of 5 to 20 years may consist of a fairly large number of storms, it is

G27

Appendix G Procedures for Conducting Frequency-of-Erosion Studies