Quantitative Risk Analysis (QRA) is a standard tool in some high-risk industries (such as the on- and offshore exploration and production and chemical industry). Presently, existing knowledge concerning human error likelihood and human reliability assessment is insufficiently represented in QRAs. In this paper we attempt to implement the quantification of the human factors in a QRA, which we call QRA+. We analysed a specific incident scenario: the risk of overfilling chemical storage tanks that operate at atmospheric pressure. This scenario was chosen because it is a relevant example of a high-risk scenario in the chemical industry. We identified relevant technological and human parameters within this scenario through on-site visits and interviews with site-experts. The quantitative knowledge concerning the technological parameters was obtained from officially documented SIL statistics, whereas the Standardized Plant Analysis Risk-Human Reliability analysis (SPAR-H) was used to quantify the human factors. Beta distributions were used to model failure probability distributions to account for the uncertainty inherent in dealing with human reliability. For seamless integration of existing qualitative and quantitative knowledge, we made use of a Bayesian Belief Network. The resulting model provides an integrated and more accurate estimation of the failure probabilities for both technological and human factors and the uncertainty surrounding such probability estimates. Furthermore, it gives insight in where these failure probabilities originate and how they interact. This will allow companies to identify those parameters they need to influence to get optimal results concerning their management of risk.

The phase-averaged wave model Simulating WAves Nearshore (SWAN) is often used for the design of dikes and harbors. However, various hindcast studies have shown that SWAN underpredicts the wave energy when waves are penetrating into bathymetries with shallow areas traversed by channels, such as tidal inlets or harbor entrances. The underprediction of these waves could lead to dike failure or shipping downtime as a consequence of incorrect hydraulic loads. This paper presents an explanation for the underprediction of this wave penetration. By comparing a series of SWAN computations with laboratory measurements and computations with the Boussinesq-type wave model TRITON, it is demonstrated that the absence of various subharmonic and superharmonic interactions in SWAN causes an unrealistic amount of energy to be trapped on the channel slopes owing to wave refraction. The two-dimensional nonlinear interactions, which appear to be present in the measurements and TRITON results, broaden the directional range of the energy density spectrum when waves propagate over a sloping bottom. Owing to the directional broadening of the spectrum, more energy exists at angles smaller than the frequency-dependent critical angle for refraction, and therefore more wave energy is transmitted into and across channels, especially when waves approach the channel under an angle. It is recommended that this insight be used to find an alternative formulation for the present one-dimensional threewave interaction formulation in SWAN.

The Guyana coastal system is characterized by very thick deposits of Amazon mud and high mud concentrations in its coastal waters. The mud deposits can be quite soft and may liquefy under incoming waves. Subsequently, the liquefied mud damps the incoming waves effectively. This paper presents a simple model to predict wave attenuation over soft (fluid) mud beds. This model is based on the two-layer approach by Gade [Gade, H.G., 1958, Effects of a non-rigid, impermeable bottom on plane surface waves in shallow water, Journal of Marine Research, 16 (2) 61-82.] which is implemented in the standard version of the state-of-the-art wave-prediction model SWAN. Input to the mud wave damping module consists of the extension, thickness, density and viscosity of the liquefied (fluid) mud layer. The model is validated against small-scale wave attenuation measurements carried out in a laboratory wave flume. The model predictions agree favourably with the experimental data. Next, the model is applied to predict wave height and wave attenuation in the Guyana coastal system. Extension and thickness of the liquefiable layer could be assessed from dual-frequency echo soundings. In the absence of field data, the density of the liquefied mud layer is obtained from literature, whereas the value of the mud's viscosity had to be established by trial and error - the selected value, though, is in the range of literature values. The model predicts significant wave attenuation. The computed changes in wave energy spectrum agree qualitatively with measurements in Surinam, whereas the decrease in significant wave height agrees more or less with historic observations along the Guyana coast.

An extensive data set of waves propagating over a shoal on a beach has been obtained from measurements in a three-dimensional physical model. The data set has been used to validate the two-dimensional Boussinesq-type wave model TRITON. In particular the performance of the implemented wave-breaking model has been investigated. Since the unique data set contains a variety of wave regimes, also the modeling of other wave aspects, such as linear dispersion and shoaling, as well as nonlinear wave-wave interaction can be verified.

A procedure is presented for the dynamic handling of the boundaries of Boussinesq-type wave models that enables to control the reflection properties. The main purpose of the procedure is the reduction of spurious reflections at open boundaries. The procedure also allows, however, the modeling of partial reflection at closed boundaries. The approach chosen takes into account the effect of wave direction, wave period, and wave height, in order that irregular waves, waves at arbitrary angles, and steep waves can all be handled properly. An innovative aspect of the developed method is that it can equally well be used for strongly dispersive waves, since besides the angle of outgoing waves also the celerity is determined dynamically. The results presented demonstrate the feasibility of the approach; reflection coefficients of only about 1% are obtained for regular waves, varying angle, period, as well as steepness.

The Boussinesq-type modeling concept provides an adequate and efficient means to describe wave dynamics in coastal regions. They are an extension of the depth-averaged shallow-water model and include the propagation of short waves as well as nonlinear effects. The Boussinesq-type model applied in this paper has been developed to obtain an accuracy sufficient for practical purposes within limited computing times. We present the extension of this model with a 2-D wave breaking model based on a combination of the eddy viscosity concept and the surface roller concept. The combination has a number of features that makes it suitable for nearshore applications. Mass and momentum are strictly conserved while the wave breaking model only dissipates energy, which is in agreement with physical laws. The results and the comparison with experiments under very different wave conditions demonstrate the good performance of the model.

There are numerous ways to derive a system of 2D Boussinesq-type wave equations from the 3D potential flow equation with free-surface boundary conditions. This freedom in design is exploited here to derive a Boussinesq-type model that has a number of unique properties. It describes the depth-integrated transport of mass and momentum in strictly conservative form. Its compact formulation is independent of the vertical reference level and allows for an efficient implementation. The model is complemented with absorbing boundary conditions that dynamically take into account the average celerity and direction of both the incoming and the outgoing wave. The model is validated by means of a number of standard test cases.