Category Archives: Models

A High-Resolution Coupled Riverine Flow, Tide, Wind, Wind Wave, and Storm Surge Model for Southern Louisiana and Mississippi, Part I: Model Development and Validation

MWR2010aA coupled system of wind, wind wave, and coastal circulation models has been implemented for southern Louisiana and Mississippi to simulate riverine flows, tides, wind waves, and hurricane storm surge in the region. The system combines the NOAA Hurricane Research Division Wind Analysis System (H*WIND) and the Interactive Objective Kinematic Analysis (IOKA) kinematic wind analyses, the Wave Model (WAM) offshore and Steady-State Irregular Wave (STWAVE) nearshore wind wave models, and the Advanced Circulation (ADCIRC) basin to channel-scale unstructured grid circulation model. The system emphasizes a high-resolution (down to 50m) representation of the geometry, bathymetry, and topography; nonlinear coupling of all processes including wind wave radiation stress-induced set up; and objective specification of frictional parameters based on land-cover databases and commonly used parameters. Riverine flows and tides are validated for no storm conditions, while winds, wind waves, hydrographs, and high water marks are validated for Hurricanes Katrina and Rita.

S Bunya, JC Dietrich, JJ Westerink, BA Ebersole, JM Smith, JH Atkinson, RE Jensen, DT Resio, RA Luettich Jr, CN Dawson, VJ Cardone, AT Cox, MD Powell, HJ Westerink, HJ Roberts (2010). “A High-Resolution Coupled Riverine Flow, Tide, Wind, Wind Wave, and Storm Surge Model for Southern Louisiana and Mississippi, Part I: Model Development and Validation.” Monthly Weather Review, 138, 345-377.

Development of Storm Surge Which Led to Flooding in St. Bernard Polder during Hurricane Katrina

OE2010Hurricane Katrina caused devastating flooding in St. Bernard Parish, Louisiana. Storm surge surrounded the polder that comprises heavily populated sections of the Parish in addition to the Lower 9th Ward section of Orleans Parish. Surge propagated along several pathways to reach levees and walls around the polder’s periphery. Extreme water levels led to breaches in the levee/wall system which, along with wave overtopping and steady overflow, led to considerable flood water entering the polder. Generation and evolution of the storm surge as it propagated into the region is examined using results from the SL15 regional application of the ADCIRC storm surge model. Fluxes of water into the region through navigation channels are compared to fluxes which entered through Lake Borgne and over inundated wetlands surrounding the lake. Fluxes through Lake Borgne and adjacent wetlands were found to be the predominant source of water reaching the region. Various sources of flood water along the polder periphery are examined. Flood water primarily entered through the east and west sides of the polder. Different peak surges and hydrograph shapes were experienced along the polder boundaries, and reasons for the spatial variability in surge conditions are discussed.

BA Ebersole, JJ Westerink, S Bunya, JC Dietrich, MA Cialone (2010). “Development of Storm Surge Which Led to Flooding in St. Bernard Polder during Hurricane Katrina.” Ocean Engineering, 37, 91-103.

Tightly Coupled, Unstructured Mesh, Wave and Circulation Models

In between presenting and writing up our work to couple tightly the SWAN and ADCIRC models, I also designed a poster for the hallway outside our lab.

It emphasizes our transition from the loose coupling with structured-mesh wave models to the tight coupling with the unstructured-mesh version of SWAN. The rectangle in the upper right and the triangle in the lower left are meant to “pop” from the sides of the poster, as shown in the picture to the right. By running on the same unstructured mesh, SWAN and ADCIRC can pass information locally, on the same core or across inter-core boundaries, without the need for global communication.

The poster itself is linked below. For more information about the SWAN+ADCIRC model, please visit my Web pages about the coupling. For a copy of our paper describing the coupled model, please contact me, and I would be happy to send it to you.

FigureGen v.41

Updated 2012/06/05: This version of FigureGen has become outdated, but is maintained on this page for reference. Please click here to be redirected to the newest version.

FigureGen is a FORTRAN program that creates images for ADCIRC files. It reads output files (fort.63, fort.64, maxele.63, etc.), grid files (fort.14, etc.), nodal attributes files (fort.13), etc. It plots contours, contour lines, and vectors. Using FigureGen, you can go directly from the ADCIRC input and output files to a presentation-quality figure, for one or multiple time snaps, without having to use SMS.

The following example depicts the water levels in ArcGIS as Ike moved through the Gulf:

Contours of water levels (m) in the Gulf of Mexico during Ike (2008), as visualized in ArcGIS.

Contours of water levels (m) in the Gulf of Mexico during Ike (2008), as visualized in ArcGIS.

This program started from a script written by Brian Blanton, and it contains code written by John Atkinson, Howard Lander, Chris Szpilka, Zach Cobell, and others. I converted it to FORTRAN because I am more familiar with that language, and I added the capability to plot vectors, among other things. But, at its core, FigureGen behaves like a script, and it uses system calls to tell other software how to generate the figure(s).

Continue reading →

Wave Refraction on Coarse Meshes

Updated 2016/07/31: This post is now outdated. SWAN has been updated to improve its treatment of the spectral propagation velocities, so these limiters are not needed. Please see this post.

Updated 2012/04/12: This is an old page. It persists on this site for posterity, but the information presented below is no longer up-to-date. When you are done here, then please click forward to this page, which describes how to control refraction errors with limiters on the spectral propagation velocities.

Updated 2011/08/30: Added a link to Part 2.

Updated 2010/02/11: Added refraction as a nodal attribute.

At the end of my instruction manual on how to compile and run SWAN+ADCIRC, I noted that wave refraction can cause problems in regions where the resolution of the bathymetry is insufficient. We worked around this problem by turning off the refraction on the local sub-meshes that were not in our region of interest. On this page, I will provide more description of exactly what can go wrong when waves are allowed to refract on coarse meshes, and I will share more details about our work-around.

It should be noted that wave refraction will always be a problem whenever any wave model is applied on a coarse mesh. This is a general numerical problem whenever the user is trying to compute waves turning over more than 90° in one spatial step. This would be a problem with SWAN, WAM, STWAVE or any other wave model, regardless of if/how they are coupled to a circulation model. As we will see, it is the coarse mesh that causes problems with wave refraction.

Continue reading →

How to Compile and Run SWAN+ADCIRC

As noted in many of my conference presentations, we have run successfully the coupled SWAN+ADCIRC model on Katrina and Rita on our SL15 mesh without any problems. This is a good sign that everything may be working correctly, but it still needs to be tested. The only way to know if the coupled model is bulletproof is by shooting a bunch of bullets at it.

Coupling-Schematic

If you want the coupled model, then please follow the link at the bottom of the ADCIRC website to request the latest release version. Here is an instruction manual on how to compile and run SWAN+ADCIRC.

Continue reading →