Boussinesq Modeling of Wave Propagation and Runup over Fringing Coral Reefs, Model Evaluation Report

Abstract

This report describes evaluation of a two-dimensional Boussinesq-type wave model, BOUSS-2D, with data obtained from two laboratory experiments and two field studies at the islands of Guam and Hawaii, for waves propagating over fringing reefs. The model evaluation had two goals: (a) investigate differences between laboratory and field characteristics of wave transformation processes over reefs, and (b) assess overall predictive capabilities of the model for reef systems with steep slopes and extended widths in shallower water. The focus in this evaluation study was on wave breaking, bottom friction parameterization, and wave setup and runup capabilities of Boussinesq wave model.In this report, the testing procedure and performance of the Boussinesq wave model are discussed. Because details of the laboratory and field studies were unavailable at the time of writing, and these are expected to be documented in other reports, only some general features of data pertinent to the numerical modeling study are presented. The time series of laboratory and field data were used in the numerical model validation study. These were converted to wave energy spectral densities, significant wave height, peak wave period, and mean water level setup for comparison to model predictions. Findings from comparisons of measurements and model calculations are presented in figures and tables, and these are supplemented as necessary with discussion of the model's capability in describing different wave processes over coral reefs. Overall, the model performed reasonably well for laboratory data with errors of less than 10 percent for the maximum runup height. For the field data, it was determined that wave energy dissipation over extremely rough coral reef surfaces could not be simply described by a quadratic bottom friction law. Reasonable model-data agreement was obtained by using an eddyviscosity type term to parameterize wave energy dissipation due to the turbulent boundary layer over rough coral reef bottoms.

On wave breaking for Boussinesq-type models

“…This is summarized in figure 7, showing a grid convergence for the gauge 3. We also would like to remark that, for Nwogu's equations and for plunging breakers, Demirbliek and Nwogu in [19] resorted to a more complex TKE closure with a PDE for the B coefficient in the production term (19). We found out that the simplified formulation adopted here, combined with the physical criteria for the initiation and termination of the process discussed in the beginning of section §4 can simulate reasonably well plunging wave breakers.…”

Water–sediment flow modeling for field case studies in Southwest China

“…For 22 example, 1-D numerical models have been efficiently used for the simulation of flow and 23 sediment processes across large spatial and temporal domains, including the CRS-1 model 24 developed by Liu (2004) at Sichuan University and the HEC model developed by USACE 25 (2003). In order to obtain more detailed flow information along the cross-sectional area, a 26 variety of 2-D numerical models have been developed (Demirbilek and Nwogu, 2007), 27 including the SMS model by Brigham University, RIVCOM by the Delft and MKE21 by the 28 DHI. As these 2-D water-sediment flow models are very CPU efficient, and meanwhile can 29 achieve sufficient accuracy in the flow simulations, they have been widely used in the 30 engineering practice.…”

HAKOU v3: SWIMS Hurricane Inundation Fast Forecasting Tool for Hawaii

“…Runup was modeled across one-dimensional, cross-shore transects using the Boussinesq model BOUSS-1D (Demirbilek and Nwogu 2007). BOUSS-1D is a time-dependent, phase-resolving model.…”