Wednesday, October 15, 2014 - 4:05pm - 6:00pm
- The First Tsunami Vertical Evacuation Structure in the United States: Ocosta Elementary School, Washington.
By Timothy J. Walsh, et al. (To be presented 21 October 2014 at the 2014 Annual Meeting of the Geological Society of America.)
Frank Gonzalez (University of Washington)
The Washington coast lies adjacent to the Cascadia subduction zone, where a magnitude 9+ earthquake and ensuing tsunami will imperil communities on low-lying spits. Three different numerical models simulating three different earthquake scenarios demonstrate that the communities of Long Beach, Westport and Ocean Shores would be inundated in a few tens of minutes, and sufficiently high ground is generally not accessible in that time.
The National Tsunami Hazard Mitigation Program (NTHMP) has developed modeling, siting, load calculation, and structural design guidance for structures that would survive a near-field earthquake and be tall and robust enough to be used for local evacuation from tsunamis.
A multi-agency planning team led by University of Washington researchers and graduate students and Washington Emergency Management Division, the Washington Department of Natural Resources, NOAA, FEMA, USGS, county and tribal emergency management officials, created a community-driven process to identify potential sites for vertical evacuation in at-risk areas. On the Westport peninsula, the principal site identified was the Ocosta Elementary School. A bond issue was recently passed (by a 70/30 majority) to create a tsunami vertical evacuation structure that could host as many as a thousand people.
- Numerical Simulation of Tidal Elevation along the West Coast of Korea
Van Nguyen (Seoul National University)
This study is to simulate tidal elevations from major constituents around the West Coast of Korea (WCK). To obtain an accurate tidal forcing at open boundaries, three well-known tidal models: two global assimilated tidal models (NAO.99b and FES2004) and one regional tidal model (NAO.99Jb), have been applied to interpolate the offshore tidal boundary conditions. In addition, a sensitivity analysis of the coastal tide elevation was implemented in order to evaluate the dependence of the tidal elevation around the WCK on the open boundary forcing and the sea bed roughness. In comparison with the change of the open boundary amplitudes, an adjustment to the bottom drag coefficients is more effective for the model calibration.
- High Performance Discontinuous Galerkin Methods for Tsunami Modeling
Rajesh Gandham (Rice University)
We describe an efficient high order discontinuous Galerkin method for accurate and faster than real time tsunami predictions. We use two dimensional shallow water PDE and nodal discontinuous Galerkin discretizations on unstructured triangular meshes for the numerical simulations. Time integration is accelerated using multirate Adams Bashforth multistep method. A positivity preserving method along with TVB slope limiter is used for the stability of numerical scheme. Our algorithms are tailored to take advantage of the single instruction multiple data architecture of graphics processing units. The implementations use OCCA, a unified multithreading approach for the portability across several hardware architectures such as CPUs, GPUs and multi-threading approaches OpenCL, OpenMP and CUDA. The efficiency of the algorithms and implementations is demonstrated using 2004 Indian Ocean Tsunami data.
- Langmuir Mixing Effects on Global Climate: WAVEWATCH III in CESM
Qing Li (Brown University)
Large-Eddy Simulations (LES) have shown the effects of ocean surface gravity waves in enhancing the ocean boundary layer mixing through Langmuir turbulence. Missing of this Langmuir mixing process in almost all the state-of-the-art climate models may contribute to the shallow biases of mixed layer depth in the Southern Ocean. In this study a third generation wave model, WAVEWATCH III, has been incorporated as a component of the NCAR Community Earth System Model (CESM1.2). In particular, the wave model is now coupled with the ocean model through a modified version of the K-Profile Parameterization (KPP) including the influence of Langmuir mixing, which is empirically based to reproduce the rate of mixing in LESs. The misalignment of wind and waves and the effects of Stokes depth are considered in parameterizing Langmuir mixing in KPP. Wave-ocean only tests show substantial improvements in the upper ocean simulation, including reductions in both the shallow biases of mixed layer depth and the low concentration biases of pCFC-11 in the Southern Ocean.
- An Improved Central-Upwind Scheme for the 2D Shallow Water System
on Triangular Grids
Jason Albright (The University of Utah)
A good numerical scheme for the 2D Saint-Venant system of
shallow water equations should satisfy two important features: the scheme
should be well-balanced --it exactly preserves “lake at rest' steady
states, and the scheme should be positivity preserving --the water depth h
There are several numerical methods which achieve this goal in the case of
fully submerged bottom topography. However, these methods will violate
well-balanced property if dry and partially dry areas (like islands and
shorelines) are present in the computational domain. To capture lake at
in such cases we introduce a new simple, conservative, well-balanced and
positivity preserving reconstruction. The proposed reconstruction is
realized in the framework of the second-order semi-discrete central-upwind
scheme from (S. Bryson, Y. Epshteyn, A. Kurganov and G. Petrova, M2AN
Math. Model. Numer. Anal., 45(3), 2011). Using several benchmark problems
we test the accuracy and robustness of this scheme.