EM 1110-2-1100 (Part II)
30 Apr 02
Example Problem II-8-2 (Continued)
The distribution of high water tide elevations above mean sea level is given by Harris (1981) for a nearby location
with similar tidal response (Figure II-8-21). For this example, the traditional joint probability method (as described
by Harris (1981)) was used to combine high-water tide frequencies with storm surge probability expressed as
frequency of occurrence per year. Combined tide and storm surge probabilities for design return periods are
included in Figure II-8-21.
Probability distribution of high tides and combined tide and storm
The north jetty will deflect a strong longshore current seaward. Therefore strong offshore-directed
currents can be expected along the north side of the jetty. Because of the local bathymetry, principally a rocky
reef parallel to shore, the current is expected to affect only the area near the jetty head. Local currents can be
estimated based on experience at similar sites (if any exist), physical modeling, and, possibly, numerical modeling.
For this example, moderate current speed is taken as 1.5 m/s and design current as 3.0 m/s. Tidal currents can
also be significant, since the tide range is fairly large. Tidal currents will affect navigation in the entrance, but are
not expected to influence jetty structural design.
Example Problem II-9-2 (Sheet 4 of 21)
Hydrodynamic Analysis and Design Conditions