Program files (Cont.)

wave simulation capability is described by Borgman and Scheffner (1991) and

Scheffner and Borgman (1992). This approach is used to generate an arbitrarily

long time sequence of simulated wave data that preserves the primary statistical

properties of the full 20-year WIS hindcast, including wave sequencing and

seasonality. Once the matrix has been computed, multiple wave field simula-

tions can be performed, with each time series stored on the file HPDSIM.OUT.

The primary advantage of using this statistically based wave simulation

approach is that the user is not limited to a finite length of data; instead, seasonal

or yearly repetitions of time series can be used for evaluations of site stability.

Each simulation will be statistically similar to the hindcast data but will contain

variability consistent with observations. If HPDPRE.OUT matrix is not avail-

able for the location of interest, one can be computed by the user or by CHL

through use of a WIS 20-year hindcast input file and execution of the program

HPDPRE. If the location of interest is not covered by the WIS hindcast data-

base, existing time series of wave height, period, and direction will have to be

supplied by the user.

The long-term simulations described above, i.e., simulations of months to

years, compute disposal mound stability as a function of residual currents speci-

fied by the user in LTFATE, the normal seasonal wave climate, and the tidal

elevation and currents computed from the specified tidal constituents in the

TIDAL.DAT file. Storm-event erosion calculations are based on surge

elevation and currents and the wave field associated with that specific event.

These data are contained in the final input file required by LTFATE, the file

STORM.DAT. This file must be assembled from existing databases or gen-

erated by the user. However, the file is required only if the user desires to

simulate the passage of a storm event over the disposal site.

The STORM.DAT file contains either a tropical or extratropical storm surge

elevation and current time series hydrograph with a corresponding storm wave

height and period corresponding to the selected event. A database of tropical

storm hydrographs for 134 historically based tropical storms has been completed

for the 486 WIS and offshore discrete locations along the east and Gulf of

Mexico coasts and for selected stations offshore of Puerto Rico. This database is

described by Scheffner et al. (1994). The companion extratropical event data-

base for the east and Gulf coasts and Puerto Rico has been completed.

A wave climate corresponding to the selected event can be obtained from

either available data (if the surge is historically based) or estimated as a function

of storm-associated or design peak wave height and periods. In the New York

Bight Mud Dump example shown in the frequency of erosion appendix, the

surge elevation and velocities were obtained from numerical simulations of the

December 1992 extratropical event. The wave field corresponding to the

December event was obtained from National Data Buoy Center data. For future

applications, surge and current information is now available in a DRP database

(reference). If wave data are not available for the selected event, then design

peak wave height and period estimates can be used.

Appendix F LTFATE Model