This quasi-linear computational scheme can be used for manual computations; however, since the calculations are répétitive, they can be
performed more efficiently by using a digital computer. When carried out
manually, the technique is lahorious, tedious and suhject to error.
Bodine (1971) gîves a computer program based on the numerical scheme
presented here. Other programs based on similar numerical schemes using
the quasi-static methods hâve been developed.
When manual computation of storm surge is necessary, a systematic,
tabular procedure must be adopted to permit stepping through ail of the
discrète computational points in space for each time incrément. Table
3-10 represents a recommended procedure. One table is required for each
time incrément. Table 3-10 corresponds to the time of peak surge for
Hurricane Camille; preceding tables required to bring the calculations to
this point are not included since those calculations are similar. The
first table in the sériés must reflect the initial conditions; thus V is
taken to be zéro and S is assumed uniform over the System.
Manual surge calculations for Hurricane Camille give a peak surge of
25.03 feet, say 25 feet (MLW) or 24.2 feet (MSL). The bottom friction
coefficient selected for this particular example was K = 0.003 and the
surge was found to be insensitive to small changes in the friction coefficient. Computer calculations using a friction coefficient of 0.003 resulted in a peak surge of 25.19 feet and a bottom friction coefficient of
0.0025 resulted in a peak surge of 25.40 feet. For some basins and storm
Systems, the bottom shear stresses are more significant in determining
water levels. Therefore, it is important to select a bottom friction
coefficient by vérification (i.e., by comparing calculated results with
observed water levels). After such vérification, the model may be used
to estimate the storm surge from hypothetical hurricanes for the same
geographical région.
The surge hydrograph (water level as a function of time) for Hurricane
Camille is shown in Figure 3^50 for the most landward computational point
on the traverse line. This figure shows that the water level rose for
about the first 8 hours, but then began to fall graduaily until about 27
hours of computational period had elapsed, then began to ri se rapidly.
A study of the local wind fields during this period shows that the winds
had an onshore component in the early stages of the storm, then the winds
began blowing offshore for several hours before the principal rise at the
coast.
, ii
A simplified method for obtaining
(b) Nomograph
sur^of a hurricane can be based
a first approximation to
s J empirical analysis of a syson an empirical analysis of past reco
,
, ,
or a combination of the
tematic set of calculations with numeri
data* from Harris (1959) with
two. Jelesnianski (1972) combined
P
of nomograms that permit the
his theoretical calculations to prod
ranhical location when a few
rapid estimation of peak surge for any geographical
parameters characterizing a storm are no
SI>
mv nx q) nermits an estimate of the peak surge
The first nomogram (Fig. 3-51) perm
ified CPI and radius of
generated by an idealized hurricane wit
p
3-115
performed more efficiently by using a digital computer. When carried out
manually, the technique is lahorious, tedious and suhject to error.
Bodine (1971) gîves a computer program based on the numerical scheme
presented here. Other programs based on similar numerical schemes using
the quasi-static methods hâve been developed.
When manual computation of storm surge is necessary, a systematic,
tabular procedure must be adopted to permit stepping through ail of the
discrète computational points in space for each time incrément. Table
3-10 represents a recommended procedure. One table is required for each
time incrément. Table 3-10 corresponds to the time of peak surge for
Hurricane Camille; preceding tables required to bring the calculations to
this point are not included since those calculations are similar. The
first table in the sériés must reflect the initial conditions; thus V is
taken to be zéro and S is assumed uniform over the System.
Manual surge calculations for Hurricane Camille give a peak surge of
25.03 feet, say 25 feet (MLW) or 24.2 feet (MSL). The bottom friction
coefficient selected for this particular example was K = 0.003 and the
surge was found to be insensitive to small changes in the friction coefficient. Computer calculations using a friction coefficient of 0.003 resulted in a peak surge of 25.19 feet and a bottom friction coefficient of
0.0025 resulted in a peak surge of 25.40 feet. For some basins and storm
Systems, the bottom shear stresses are more significant in determining
water levels. Therefore, it is important to select a bottom friction
coefficient by vérification (i.e., by comparing calculated results with
observed water levels). After such vérification, the model may be used
to estimate the storm surge from hypothetical hurricanes for the same
geographical région.
The surge hydrograph (water level as a function of time) for Hurricane
Camille is shown in Figure 3^50 for the most landward computational point
on the traverse line. This figure shows that the water level rose for
about the first 8 hours, but then began to fall graduaily until about 27
hours of computational period had elapsed, then began to ri se rapidly.
A study of the local wind fields during this period shows that the winds
had an onshore component in the early stages of the storm, then the winds
began blowing offshore for several hours before the principal rise at the
coast.
, ii
A simplified method for obtaining
(b) Nomograph
sur^of a hurricane can be based
a first approximation to
s J empirical analysis of a syson an empirical analysis of past reco
,
, ,
or a combination of the
tematic set of calculations with numeri
data* from Harris (1959) with
two. Jelesnianski (1972) combined
P
of nomograms that permit the
his theoretical calculations to prod
ranhical location when a few
rapid estimation of peak surge for any geographical
parameters characterizing a storm are no
SI>
mv nx q) nermits an estimate of the peak surge
The first nomogram (Fig. 3-51) perm
ified CPI and radius of
generated by an idealized hurricane wit
p
3-115