EM 1110-2-1100 (Part II)
30 Apr 02
EXAMPLE PROBLEM II-8-2
FIND: Hydrodynamic parameters for design of the north jetty. The intended design life is 25 years.
GIVEN: Two jetties are being designed at a site exposed
to energetic waves and currents (Figure II-8-18). The
jetties extend from shore to a depth of -10 m MLLW. A
representative bottom slope is 1/100. Water level and
wave measurements near the site are available at 6-hr
intervals over a period of 17 years.
Note: This period of measurement is unusually
long for coastal engineering project sites.
Typically information on water levels and waves
must be generated by numerical modeling to
supplement limited measurements. The level of
confidence in any calculated results depends
highly on the quality of available water level and
wave information. The level of detail and Figure II-8-18.
Jetty plan
refinement of calculations should be consistent
with the quality of available information and
project needs.
SOLUTION:
WATER LEVEL:
Assume all storm populations that could affect design are well-represented (both number and intensity
of events) in the data.
Note: At sites exposed to tropical storms, the assumption that storms are well-represented in the
historical record at the site is often not justified. In such cases, a numerical model study is
required to adequately represent the range of possibilities (Part II-5).
Datums. Datum information for the site (obtained from NOS tidal benchmark sheet; see Part II-8) is listed in
Table II-8-12.
Table II-8-12
Tidal Datum Information
Datum
Abbreviation
Level (m)
Mean higher high water
MHHW
2.55
Mean high water
MHW
2.34
Mean tide level
MTL
1.38
Mean sea level
MSL
1.36
National Geodetic Vertical Datum
NGVD
1.26
Mean low water
MLW
0.42
Mean lower low water
MLLW
0.00
Example Problem II-9-2 (Sheet 1 of 21)
Hydrodynamic Analysis and Design Conditions
II-8-35
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