6. Wave Run-up and Overtopping
189
It is a common practice to express the effect of surface texture of the
slope’s surface to a coefficient of roughness defined as the ratio of the
rough to smooth run-up. The roughness coefficient for the different types
of textures of the slopes with or without the armour layers are provided
in Table 6.1. For composite slopes Saville [1958] suggested that a rational approximation of run-up could be related to a corresponding slope
that traverses the actual slope at the position of the breaker point and
the maximum run-up. This requires an itérative solution to résolve and
will under-estimate the run-up measured for concave slopes. The introduction of a berm into a slope can provide a very effective means of reducing
run-up provided the width of the berm represents a significant part, say
20% of the wavelength. This is typically of the order of 10 m for shallow
water Coastal defence structures. A berm is also generally most effective
when positioned at or above the MSL. In an environment exposed to a
high tidal range, the definitive level will often be taken as mean high water
springs or that determined from a joint wave and water level probability
analysis.
Battjes [1974] extended the formula of Hunt [1959] for regular to irregular waves using the time-domain wave parameters. The formula for the
relative wave run-up is as follows:
-^2%
Hs
— CvnCm
(6.6)
Cm
tan a
(6.7)
Sm
Lm
(6.8a)
L'm
= A
2tt
(6.8b)
where, Cm — 1.49-1.87, R<2% = Run-up exceeded by 2% of the number of
incident waves.
a = slope of the structure and Tm = mean wave period.
Another set of run-up data for smooth slopes is presented by Waal and
van der Meer [1992] for, Cm > 2.0,
^u2% _ g q
(6.9)
(AG)toe
189
It is a common practice to express the effect of surface texture of the
slope’s surface to a coefficient of roughness defined as the ratio of the
rough to smooth run-up. The roughness coefficient for the different types
of textures of the slopes with or without the armour layers are provided
in Table 6.1. For composite slopes Saville [1958] suggested that a rational approximation of run-up could be related to a corresponding slope
that traverses the actual slope at the position of the breaker point and
the maximum run-up. This requires an itérative solution to résolve and
will under-estimate the run-up measured for concave slopes. The introduction of a berm into a slope can provide a very effective means of reducing
run-up provided the width of the berm represents a significant part, say
20% of the wavelength. This is typically of the order of 10 m for shallow
water Coastal defence structures. A berm is also generally most effective
when positioned at or above the MSL. In an environment exposed to a
high tidal range, the definitive level will often be taken as mean high water
springs or that determined from a joint wave and water level probability
analysis.
Battjes [1974] extended the formula of Hunt [1959] for regular to irregular waves using the time-domain wave parameters. The formula for the
relative wave run-up is as follows:
-^2%
Hs
— CvnCm
(6.6)
Cm
tan a
(6.7)
Sm
Lm
(6.8a)
L'm
= A
2tt
(6.8b)
where, Cm — 1.49-1.87, R<2% = Run-up exceeded by 2% of the number of
incident waves.
a = slope of the structure and Tm = mean wave period.
Another set of run-up data for smooth slopes is presented by Waal and
van der Meer [1992] for, Cm > 2.0,
^u2% _ g q
(6.9)
(AG)toe