Arjen MARKUS (Deltares, Netherlands)
Keywords: Tcl, hydrodynamics, dike, flood, Linux, Cluster, statistics
The safety of (river) dikes in the Netherlands, located in the delta
of the rivers Rhine, Meuse and Scheldt, has been the subject of debate
for more than ten years. Most methods to estimate the required dike
height, as part of the risk assessment focus on the river only. If,
however, a river dike breaks somewhere along the river, this influences
the chance of dike breaches elsewhere: the water level downstream may
be lowered, but the water can now reach the dikes around the flooded
area from the inland side. This effect is known as river system
behaviour.
To understand the importance of this effect and the possible
consequences it has on the design methodology, we studied the
hydrodynamics of a part of the Netherlands that is enclosed
by the Rhine and Meuse. A major part of that study was to conduct
several hundreds of simulations with different dike strength parameters
and model flood wave to enable a statistical analysis of the risks in
this area, vis-a-vis casualties and economic damage if a dike breaks.
This involved getting a set of otherwise independent programs to work
together: the dike strength and flood parameters were selected via a
Monte Carlo method, this led to input for a detailed hydrodynamic model
of the rivers and the surrounding area and results from that model were
analysed to estimate casualties and economic damage.
As these programs ran on different types of computers in different
locations, Tcl programs were developed to automate the transfer of the
input and output, the scheduling of the programs on the Linux cluster
and local PCs and the checking of the computations. Furthermore, Tcl
programs facilitated in collecting the results in a condensed form,
useful for the subsequent statistical analysis.
While the framework as such was set up in an ad hoc manner, there is an
elegant underlying formal model: the tuplespace that describes this
framework very well. The file system of the Linux cluster served as
the database system and Tcl's abilities to interact with the OS and
the file system (both on Linux and PC) were instrumental in managing
the actual computations.
Delft Hydraulics, GeoDelft, the Subsurface and Groundwater unit of TNO
and parts of Rijkswaterstaat have joined forces in a new independent
institute for delta technology, Deltares. Deltares combines knowledge
and experience in the field of water, soil and the subsurface. We
provide innovative solutions to make living in deltas, coastal areas and
river basins safe, clean and sustainable.
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