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You are here : eLibrary : IAHR World Congress Proceedings : 36th Congress - The Hague (2015) ALL CONTENT : Special sessions : A consistent suite of models for flood risk management
A consistent suite of models for flood risk management
Consistent flood risk management is only possible if the tools to analyse policy and to implement the policy are
consistent. Policy tools, flood defence assessment tools, design tools, flood forecasting tools have different requirements
for computation times, accuracy, spatial and temporal scale. Moreover tools for use by the national water Authority
(Rijkswaterstaat) for the regional water authorities (Water Boards) have been developed by different (sub) contractors.
This means obtaining mutual consistency between the tools is challenging. The national government is responsible for
the tools for national water systems, STOWA (the training and research organisation for the regional water authorities)
and provincial governments are responsible for the regional water systems. As developers from different government
organisations Rijkswaterstaat and STOWA working with research institutes as Deltares and private contractors (as HKV)
we have greatly reduced the number of User Interfaces, made use of common libraries for failure modes and
probabilistic analysis. Data definitions and exchange formats have been essential in this process, work flows become
easier to manage.
- The same Hydrodynamic models for water levels (SOBEK and WAQUA) en wave propagation (SWAN) are
used in all processes.
- Schematisations of water systems can differ due to the scenario (present, future or past). Flood forecasting
tools are updated and or verified every year. Flood defence assessment tools, including hydraulic boundary
conditions are updated every 6 to 12 years.
- In the last 5 years the national and regional authorities have integrated probabilistic tools to calculate hydraulic
loads for the national water systems (Hydra-model-suite) and implemented similar tools for the regional water
systems (PROMOTOR). The Hydra-tools were developed for assessment but have been used in policy analysis
and dike design since 2006. They are a major part of the design method consistent with the new flood risk
standards en methodology introduced in 2014. These probabilistic models provide hydraulic boundary
conditions (waves and water level for each chosen return period. They also provide the design height for dikes.
- The tools to evaluate dike strength for regional flood defences (15000 km) (DAM) has been used for policy
analysis of the national flood defences (3600 km). The framework and concept of this tool is being used to
develop the new safety assessment tool, ¡°Ringtoets¡±, for the national (¡°primary¡±) flood defences in 2017. Dam
was also used in the Delta Program to make rapid designs for the costing tool (Koswat). Using the DAM module
for piping and slope stability the main characteristics of a dike could be determined rapidly: ¡°foot print¡±, the
width of the dike. A wider dike means more material, expropriation of land, replacement of buried utility lines
and demolition of houses, the main indicators for dike costs.
- Indicators for policy tools (cost-benefit analysis, societal risk, individual risk) have been provided using these
models Promotor, DAM (future dimensions for dikes), Hydra (probability of flooding, hydraulic boundary
conditions and design height for future scenario¡¯s, Koswat (costs for dike improvement).
Given the above, it is also a fact that governors, managers, and government or regional officials have new policy
questions, and need answers fast. The national and regional water authorities therefore have to be flexible, and should
be able to use, adapt, and expand the instruments to cope with new policy questions. However, there is a major
drawback to keep developing new tools for every policy question: the danger of inconsistencies. Therefore the national
water authorities have greatly reduced the number of separate instruments, and made use of common software (such as
libraries for failure modes and probabilistic analysis). Proper definitions of data format, and the way they are exchanged
have been essential in this process. Consistent models are important for long term and short term policy choices and the
evaluation of measures, and for explaining the level of a flood alert. Inconsistency definitely costs money and may cost
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Chapter : IAHR World Congress Proceedings
Category : 36th Congress - The Hague (2015) ALL CONTENT
Article : Special sessions
Date Published : 12/08/2015
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