  The Northern European Enclosure Dam (NEED) is a hypothetical project to
prevent flooding in European countries following the rising ocean level due to
melting arctic glaciers. This project involves the construction of two large
dams between Scotland and Norway, as well as England and France. The
anticipated cost of this project is 250 to 500 billion euros. In this paper, we
present the simulation of the aftermath of flooding on the European coastline
caused by a catastrophic break of this hypothetical dam. From our simulation
results, we can observe that there is a traveling wave after the accident, with
a velocity of around 10 kilometers per hour, raising the sea level permanently
inside the dammed region. This observation implies a need to construct
additional dams or barriers protecting the northern coastline of the
Netherlands and the interior of the Baltic Sea. Our simulations have been
obtained using the following building blocks. First, a graph transformation
model was applied to generate an adaptive mesh approximating the topography of
the Earth. We employ the composition graph grammar model for breaking
triangular elements in the mesh without the generation of hanging nodes.
Second, the wave equation is formulated in a spherical latitude-longitude
system of coordinates and solved by a high-order time integration scheme using
the generalized $\alpha$ method.
