Sea Change

2014/05/28 – NC State Engineering Magazine
Working with one of North Carolina’s most valuable resources

Dietrich came to NC State with a wealth of experience in coastal modeling, most of it done along the Gulf Coast of the United States. He will soon begin a project with the National Oceanic and Atmospheric Administration to model North Carolina’s coast.

Dietrich is part of a research community using a computer model called ADCIRC to predict everything from storm surge and flooding to the feasibility of dredging, or where material floating in the ocean might end up.

When a hurricane is bearing down on the coastline, running the models quickly is of the essence. But the faster the model runs, the less accurate it is. Improving the models so that the time and accuracy trade-off isn’t as sharp is part of Dietrich’s work.

So is figuring out the best ways to visualize the results and get the modeling information to local emergency management officials along the coast so that they can use it.

“It doesn’t help anybody if we are doing this in an empty room somewhere and not sharing the results with the community and sharing them in a way that will maximize their use and maximize their impact,” he said.

Read the rest of this entry »

Hazard Resilience in Coastal Communities

2014/05/14 – North Carolina Sea Grant Coastwatch
Coastal Science Serves North Carolina: Sea Grant Funds New Research Projects

Using a high-resolution modeling system, the researchers will expand the utility and accuracy of wave, storm-surge and flooding forecast guidance available to emergency managers in North Carolina. The accurate prediction of these elements is essential for the safety of people and property.

Presentation: CARTHE 2014

JC Dietrich, A Muhammad, CN Dawson. “Update on ADCIRC Coupling for Nearshore Simulations of Hurricane Isaac and SCOPE.CARTHE All-Hands Meeting, Hollywood, Florida, 30 April 2014.

Please click here for more information about CARTHE.

Read the rest of this entry »

Characterizing Hurricane Storm Surge Behavior in Galveston Bay using the SWAN+ADCIRC Model

The SWAN+ADCIRC shallow-water circulation model, validated for Hurricane Ike (2008), was used to develop five synthetic storm surge scenarios for the upper Texas coast in which wind speed was increased and landfall location was shifted 40 km westward. The Hurricane Ike simulation and the synthetic storms were used to study the maximum water elevations in Galveston Bay, as well as the timing and behavior of surge relative to the hurricane track. Sixteen locations indicative of surge behavior in and around Galveston Bay were chosen to
for analysis in this paper. Results show that water surface elevations present in Galveston Bay are dominated by the counterclockwise hurricane winds and that increasing wind speeds by 15% results in approximately 23% (+/−3%) higher surge. Furthermore, shifting the storm westward causes higher levels of surge in the more populated areas due to more intense, higher shore-normal winds. This research helps to highlight the vulnerability of the upper Texas Gulf Coast to hurricane storm surge and lends insight to storm surge and flood mitigation studies in the Houston–Galveston region.

AG Sebastian, JM Proft, JC Dietrich, W Du, PB Bedient, CN Dawson (2014). “Characterizing Storm Surge Behavior in Galveston Bay using the SWAN + ADCIRC Model.Coastal Engineering, 88, 171-181, DOI: 10.1016/ j.coastaleng.2014.03.002.

A Discontinuous Galerkin Coupled Wave Propagation/Circulation Model

On large geographic scales, ocean waves are represented in a spectral sense via the action balance equation, which propagates action density through both geographic and spectral space. In this paper, a new computational spectral wave model is developed by using discontinuous Galerkin (DG) methods in both geographic and spectral space. DG methods allow for the use of unstructured geographic meshes and higher-order approximations for action propagation in both geographic and spectral space, which we show leads to increased accuracy. This DG spectral wave propagation model is verified and validated through comparisons to manufactured and analytic solutions as well as to the Simulating WAves Nearshore (SWAN) model. Coupled wave/circulation models are needed for many applications including for the interaction between waves and currents during daily wind and tide driven flows. We loosely couple the newDGspectralwavemodel to the DG Shallow Water Equation Model (DG-SWEM), an existing DG circulation model. In addition to formulating the DG method for the coupled wave/circulation model, we derive an a priori error estimate. Preliminary numerical results of the DG coupled wave/circulation model are presented with comparisons to DG-SWEM coupled tightly to SWAN.

JD Meixner, JC Dietrich, CN Dawson, M Zijlema, LH Holthuijsen (2014). “A Discontinuous Galerkin Coupled Wave Propagation/Circulation Model.Journal of Scientific Computing, 59, 334–370, DOI: 10.1007/s10915-013-9761-5.