Jul 28

US Congress on Computational Mechanics (USNCCM12)

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M.V. Bilskie, S.C. Medeiros, S.C. Hagen, “Development of a High-Resolution Tide-, Wind-, and Wave-Driven Ocean Circulation Model for the Northern Gulf of Mexico.” 12th International Congress on Computational Mechanics, Raleigh, NC, July 22-25, 2013.

Abstract:The northern Gulf of Mexico is a complex hydrodynamic system including low-lying topography and networks of rivers, bays, marshlands, the Intracoastal Waterway system, along with a wide and flat continental shelf. The intricate geometry creates an interesting scenario for studying sea level rise and hurricane storm surge. To capture the hydrodynamic response to sea level rise and hurricane storm surge, a large-scale, high-resolution wind-wave, tide, and hurricane storm surge model was developed that incorporates a tightly coupled shallow water coastal circulation model and wind wave model (ADCIRC+SWAN). With any coastal inundation model, the overland topography and frictional parameterizations are crucial to the simulated hydrodynamics. Sub-scale terrain features were incorporated into an unstructured finite element mesh and elevations were assigned from interpolating lidar- and survey-derived digital terrain models using a cell averaging method to minimize vertical errors in elevation (Bilskie and Hagen, 2013).

In addition, surface roughness parameters (i.e. Manning’s n, surface canopy, and surface directional effective roughness length [Z0]) were generated from an enhanced parameterization scheme that uses lidar point cloud data to augment look-up tables based on land cover databases. The preliminary finite element mesh contains ~4 million nodes and provides full coverage from the Bay of St. Louis, MS to Apalachee Bay, FL. Mesh resolution in the Gulf is near 5 kilometers, 1 kilometer on the continental shelf, 100 meters along the shoreline, and down to 40 meters in marsh regions and small channels.
Validation consisted of two historical events, Hurricane Katrina and the Deepwater Horizon oil spill (DWH). Hurricane Katrina was simulated and results were compared to observed water levels and recorded high water marks. Simulated inundation area for the DWH was compared to satellite-based observations of the inundation area from processed SAR (synthetic aperture radar) imagery (Medeiros, et al., 2012).

REFERENCES

Bilskie, M. V., and Hagen, S. C. (2013). “Topographic Accuracy Assessment of Bare Earth Lidar-Derived Unstructured Meshes.” Advances in Water Resources, 52, 165-177.
Medeiros, S. C., Hagen, S. C., Chaouch, N., Feyen, J. C., Temimi, M., Weishampel, J. F., Funakoshi, Y., and Khanbilvardi, R. (2012). “Assessing the Performance of a Northern Gulf of Mexico Tidal Model Using Satellite Imagery.” Coastal Engineering, In Review.

 

Permanent link to this article: http://www.mattbilskie.com/us-congress-on-computational-mechanics/

Jul 25

Publication | Topographic Accuracy Assessment of Bare Earth lidar-derived Unstructured Meshes

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M.V. Bilskie, S.C. Hagen (2013). “Topographic Accuracy Assessment of Bare Earth idar-derived Unstructured Meshes.” Advances in Water Resources, 52, 165-177,http://dx.doi.org/10.1016/j.advwatres.2012.09.003

This study is focused on the integration of bare earth lidar (Light Detection and Ranging) data into unstructured (triangular) finite element meshes and the implications on simulating storm surge inundation using a shallow water equations model. A methodology is developed to compute root mean square
error (RMSE) and the 95th percentile of vertical elevation errors using four different interpolation methods (linear, inverse distance weighted, natural neighbor, and cell averaging) to resample bare earth lidar and lidar-derived digital elevation models (DEMs) onto unstructured meshes at different resolutions. The results are consolidated into a table of optimal interpolation methods that minimize the vertical elevation error of an unstructured mesh for a given mesh node density. The cell area averaging method performed most accurate when DEM grid cells within 0.25 times the ratio of local element size and DEM cell size were averaged. The methodology is applied to simulate inundation extent and maximum water levels in southern Mississippi due to Hurricane Katrina, which illustrates that local changes in topography such as adjusting element size and interpolation method drastically alter simulated storm surge locally and non-locally. The methods and results presented have utility and implications to any modeling application that uses bare earth lidar.

Permanent link to this article: http://www.mattbilskie.com/topographic-accuracy-assessment-of-bare-earth-lidar-derived-unstructured-meshes/

May 25

Integrated Modeling of Hydrodynamics and Marsh Evolution Under Sea Level Rise in Apalachicola, Florida

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K. Alizad, M.V. Bilskie, D. Passeri (2013). “Integrated Modeling of Hydrodynamics and Marsh Evolution Under Sea Level Rise.” Florida Watershed Journal, http://www.flwatershedjournal.org/?p=248.

The northern Gulf of Mexico is home to a vast amount of coastal ecosystems that provide natural and economic resources. Rising sea levels may threaten these resources with increased flood magnitude and frequency, accelerated erosion, loss of wetlands, and saltwater intrusion. The Ecological Effects of Sea Level Rise in Northern Gulf Of Mexico (EESLR-NGOM), a five year interdisciplinary effort funded by the National Oceanic and Atmospheric Administration (NOAA), aims to assess these effects and provide local coastal managers with the knowledge and tools to prepare for the dynamic impacts of tides and storm surge magnified by sea level rise (SLR). The project builds on field observations centered at three National Estuarine Research Reserves (NERR) including Apalachicola, Grand Bay and Weeks Bay. The field observations aid in the development, parameterization and validation of integrated models (e.g. hydrodynamic and biologic) to predict the response of the coastal system under various SLR scenarios.

The accurate development and parameterization of these models is crucial for simulating future sea level rise scenarios; however, modeling the physical processes of estuaries can be challenging due to their complex nature. To accomplish this, hydrodynamic, sediment transport and biological models are integrated, as their respective processes depend on and interact with one another.

Continue Reading…

Permanent link to this article: http://www.mattbilskie.com/ntegrated-modeling-of-hydrodynamics-and-marsh-evolution-under-sea-level-rise-in-apalachicola-florida/

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