136
6 Prospects: Approaches of Integrated Management
the damage depends on several items some of which have already been mentioned. The
design water level has to be calculated as described in Sect. 5.2. The significance of these
uncertainties inherent in the determination for decisions on coastal protection are comprehensively described, for example, in Kunz (2004). Associated with the design water level
is the probability of failure of a main dike; this probability should be as low as possible
and it should be the same for the entire German coast.
3 The same probability of failure
leads to different risks because there are differences in the vulnerability of rural and urban
areas behind the dike. In the Netherlands the concept acknowledged the different degree of
vulnerability with the different safety levels ranging from 1 to 10,000 (densely inhabited
Delta area) to 1 to 1250 along the rivers (Fig. 5.6 on p. 71).
The design water level in Germany is the result of the societal decision-making process. The duty of coastal protection is the protection of people and their property against
flooding. This societal demand implicates that the embankments should be built as safe as
possible. But the question is how to define the term “as safe as possible”? Answering the
question requires to consider that the flood-prone area has to be protected against flooding
by a technical structure (i.e., dike) which height is determined by taking into account the
highest storm tide, the wave run-up and the fact that guarantee via absolute safety is not
possible. Obviously, the main problem is that the highest storm tide cannot be determined and all attempts to do so display remaining uncertainties. A safety standard has to
be defined which is able to fulfill the subjective impression of safety for the public and
provide an applicable safety standard for a construction. Consequently, the safety standard
is not defined for the flood-prone area, it is defined for the technical structure. Over the
last decades the safety standard, as defined by the Engineering Committee (Engineering
Committee, 1962), has met public requirements. The safety standard is incorporated in a
protection concept which guarantees a defined safety or an accepted risk and reasonable
costs for the implementation (Kunz, 2004).
In this context, Giszas (2003) and Kunz (2004) refer to the ALARP concept (As Low
As Reasonably Practicable), which is a modified version of the risk classification by the
WBGU. The ALARP concept divides the risk into three main groups: (a) acceptable risk,
(b) tolerable risk and (c) non-tolerable risk. The ALARP area is the area between acceptable risk on the one hand and non-tolerable risk on the other hand. Kunz (2004) divides
the technical part of the protection approach into:
(a) definition of the critical (decisive) high water level,
(b) definition of the decisive wave run-up and acceptable over-topping rate,
(c) periodical inspection and improvement of safety status,
(d) technical standards and recommendations for the construction and maintenance of
coastal protection infrastructure and
(e) reduction of risk by the introduction of additional embankments.
3 Legally binding specification in the State Law on Dikes in Lower Saxony, Germany.
6 Prospects: Approaches of Integrated Management
the damage depends on several items some of which have already been mentioned. The
design water level has to be calculated as described in Sect. 5.2. The significance of these
uncertainties inherent in the determination for decisions on coastal protection are comprehensively described, for example, in Kunz (2004). Associated with the design water level
is the probability of failure of a main dike; this probability should be as low as possible
and it should be the same for the entire German coast.
3 The same probability of failure
leads to different risks because there are differences in the vulnerability of rural and urban
areas behind the dike. In the Netherlands the concept acknowledged the different degree of
vulnerability with the different safety levels ranging from 1 to 10,000 (densely inhabited
Delta area) to 1 to 1250 along the rivers (Fig. 5.6 on p. 71).
The design water level in Germany is the result of the societal decision-making process. The duty of coastal protection is the protection of people and their property against
flooding. This societal demand implicates that the embankments should be built as safe as
possible. But the question is how to define the term “as safe as possible”? Answering the
question requires to consider that the flood-prone area has to be protected against flooding
by a technical structure (i.e., dike) which height is determined by taking into account the
highest storm tide, the wave run-up and the fact that guarantee via absolute safety is not
possible. Obviously, the main problem is that the highest storm tide cannot be determined and all attempts to do so display remaining uncertainties. A safety standard has to
be defined which is able to fulfill the subjective impression of safety for the public and
provide an applicable safety standard for a construction. Consequently, the safety standard
is not defined for the flood-prone area, it is defined for the technical structure. Over the
last decades the safety standard, as defined by the Engineering Committee (Engineering
Committee, 1962), has met public requirements. The safety standard is incorporated in a
protection concept which guarantees a defined safety or an accepted risk and reasonable
costs for the implementation (Kunz, 2004).
In this context, Giszas (2003) and Kunz (2004) refer to the ALARP concept (As Low
As Reasonably Practicable), which is a modified version of the risk classification by the
WBGU. The ALARP concept divides the risk into three main groups: (a) acceptable risk,
(b) tolerable risk and (c) non-tolerable risk. The ALARP area is the area between acceptable risk on the one hand and non-tolerable risk on the other hand. Kunz (2004) divides
the technical part of the protection approach into:
(a) definition of the critical (decisive) high water level,
(b) definition of the decisive wave run-up and acceptable over-topping rate,
(c) periodical inspection and improvement of safety status,
(d) technical standards and recommendations for the construction and maintenance of
coastal protection infrastructure and
(e) reduction of risk by the introduction of additional embankments.
3 Legally binding specification in the State Law on Dikes in Lower Saxony, Germany.