Model simulations

representing the 99-hr time sequences for each of the 16 tropical storm events

and the 144-hr time sequences for each of the 38 extratropical storm events were

input to LTFATE.

Model simulations

The six Mud Dump ambient depth/mound height combinations were sub-

jected to the 64 tropical storm surge hydrographs (16 storms times four possible

tide phases) to evaluate the erosion potential of the configurations shown in

Table G4. An identical procedure was followed for the 152 extratropical storm

surge hydrographs (38 storms times four possible tide phases). In all six simula-

tions for each type of storm, the maximum vertical erosion experienced at any

location on the mound during each of the simulations was archived for use in the

EST to develop vertical erosion versus frequency-of-occurrence relationships.

EST Input File Development

As noted earlier, EST is a statistical procedure that uses a limited database of

historical occurrences to generate multiple simulated scenarios from which fre-

quency relationships and error estimates can be computed. The EST requires

two types of input. The first set represents descriptive storm parameters that

define the dynamics of each storm event. These parameters, referred to as input

vectors, should be (a) tidal phase, (b) duration of the event measured as the

number of hours during which the computed transport magnitude exceeds 10.0

10-4 ft3/sec/ft-width, (c) maximum transport magnitude computed during the

storm event, (d) wave height, (e) wave period, and (f) maximum depth-averaged

velocity magnitude associated with the maximum transport value.

The second input parameter represents a measure of damage resulting from

the passage of the storm event. These parameters are referred to as response

vectors. Typical response vectors are storm surge elevation, shoreline erosion,

dune recession, flood inundation, or for capping projects, vertical erosion.

Tropical storm vectors

Input and response vectors for hurricanes #296, 327, 748, and 835 for high

water after flood (maximum tidal surface elevation) for the site scenario of an

8-ft mound located in 83 ft of water are shown in Table G6.

The EST uses the parameters of Table G6 for all tropical storm events and

each of the four tidal phases as a basis for simulating multiple repetitions of

multiple years of storm activity. In this application, 100 repetitions of a 200-year

sequence of storm activity were simulated for the six scenarios shown in

Table G6. As mentioned above, the EST assumes that future storm activity will

be similar to past events, i.e., a hurricane such as Camille, which devastated the

G21

Appendix G Procedures for Conducting Frequency-of-Erosion Studies