Wave Field Hydrograph Development

hydrographs represents a combination of the surge hydrograph with the tidal

hydrographs generated for the four phases of the tide based on the M2 tidal

constituent.

Wave Field Hydrograph Development

Waves are a critical component of LTFATE input. This section recommends

procedures for providing input waves for both tropical and extratropical storms.

Tropical storms

Because LTFATE does not have a storm wave field component, a methodol-

ogy was adopted from the Shore Protection Manual (SPM) (Headquarters,

Department of the Army 1984). The approximation reported in the SPM gives

an estimate of the deepwater significant wave height and period at the point of

maximum wind for a slowly moving hurricane. A full numerical hindcast of the

wave field associated with the historical event would be more accurate than the

adopted procedure; however, the SPM approach is expected to be adequate for

the purposes of most erosion frequency studies.

The wave height and period are given by the following formulae:

0.208 VF

(G1)

16.5 e

100

and

0.104 VF

(G2)

8.6 e

200

where

Ho = deepwater significant wave height in feet

Ts = corresponding significant wave period in seconds

R = radius to maximum wind in nautical miles

Dp = pn - po, where pn is the normal pressure of 29.93 in. of mercury and

po is the central pressure of the hurricane

VF = forward speed of the hurricane in knots

G14

Appendix G Procedures for Conducting Frequency-of-Erosion Studies