Uncertainties in the Prediction of Design Waves

Based on extensive hydraulic model testing, the uncertainties
of available „standard“ models used to predict wave heights on shallow
foreshores of coastal structures are quantified. Both wave
transformation on the foreshore and at the structure are taken into
account. Finally, improvements of the prediction models are proposed
and recommendations on the selection of the models to be used are
provided.

One of the prerequisites to help moving sustainable design of coastal protection
from an academic debate into the realm of concrete work, performance and return is the
development and use of probabilistic design tools (OUMERACI; 2000). However, the
implementation of a reliability based design implies among others that the uncertainties
associated with the prediction of wave conditions at the design site should be reliably
assessed. In fact, small errors in estimating design waves may result in much larger
errors for thep redicted wave loads, wave overtopping, structure stability, etc.. One of
the main results of a large European research project on reliability based design of
coastal structures was that most uncertainties still originate from the errors in
predicting wave transformation from deep water towards shallow foreshores
(OUMERACI et al.; 2001). Therefore, a basic research project was initiated by the
authors to determine the uncertainties associated with the prediction of wave
transformation on shallow foreshores and in presence of coastal structures with
different reflection properties. The project has just been completed and the results of
the whole project have been summarized in a final report (OUMERACI and
MUTTRAY, 2001).

This paper is intended to principally discuss some of the results by focusing on
the uncertainties associated with the prediction of wave heights on shallow foreshores
and in the presence of coastal structures.

1. Senior Coastal Engineer; Delta Marine Consultants bv; P.O. box 63; 2800 AB Gouda, The
   Netherlands; mmuttray@dmc.nl
2. Professor and Head of Leichtweiß-Institute for Hydraulic Engineering; Beethovenstr. 51a;
   38106 Braunschweig, Germany; h.oumeraci@tu-bs.de
3. Teaching and Research Assistant; Leichtweiß-Institute; m.bleck@tu-bs.de

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Muttray_et_al_Waves01_2001.pdf