Discipline: Technology and Engineering
Subcategory: Civil/Mechanical/Manufacturing Engineering
Simbarashe Kanjanda - Tennessee State University
Co-Author(s): Muhammad Akbar,Tennessee State University, Nashville, TN
This paper focuses on parametrically studying effect of bottom friction and surface roughness length using ADCIRC+SWAN model. Capturing friction and surface roughness accurately is essential in obtaining accurate water levels in storm surge modelling. Reliable model results are essential to emergency management officials and the public to aid decision-making and ensure loss of life is minimized. Results also need to be accurate for design and risk analysis’ objective of designing coastal protection structures and assessing risk that drives local development as well as government subsidized insurance.
The ADvanced CIRCulation (ADCIRC) model makes use of a continuous- Galerkin solution of the Generalized Wave Continuity Equation (GWCE), and the depth-integrated momentum equations on an unstructured, finite-element mesh. Elevation is obtained from the solution of the depth-integrated continuity equation in Generalized Wave-Continuity Equation (GWCE) form. Velocity is obtained from the solution of the momentum equations. Simulating WAves Nearshore (SWAN) model makes use of wave action balance equation spectra propagation. SWAN takes into account generation by wind, whitecapping, depth-induced wave breaking and nonlinear interactions. Integrated and tightly coupled ADCIRC and SWAN run on the same global unstructured mesh resulting in the SWAN+ADCIRC model.
In this study a spatially varying Manning’s n bottom friction and surface roughness length was applied. Manning’s n and surface roughness length values were derived from land-use databases. A parametric matrix was developed to analyze the effect of friction and surface roughness applying higher and lower values than derived from land-use databases.
The model is used to hindcast Hurricane Rita (2005). The simulated water levels are compared to published data. In the region of landfall, modeled with manning’s n and surface roughness length values derived from land-use databases at the coastal locations, there was significant under prediction of the peak water levels. At the inland locations, there is accurate prediction at some of the locations and under prediction at the other locations. The Hurricane Rita, 2005 storm surge will be simulated with different combinations of bottom friction and roughness length values from the parametric matrix.
References: Kerr, P. C., et al. (2013), U.S. IOOS coastal and ocean modeling testbed: Inter-model evaluation of tides, waves, and hurricane surge in the Gulf of Mexico, J. Geophys. Res. Oceans, 118, 5129-5172, doi:10.1002/jgrc.20376.
Booij, N., R. Ris, and L. Holthuijsen (1999), A third-generation wave model for coastal regions: 1. Model description and validation, J. Geo-phys. Res., 104(C4), 7649-7666.
Dietrich, J.C., Zijlema, M., Westerink, J.J., Holthuijsen, L.H., Dawson, C.N., Luettich, R.A. Jr., Jensen,R.E., Smith, J.M., Stelling, G.S., Stone, G.W.: Modeling hurricane waves and storm surge using integrally-coupled, scalable computations. Coast. Eng. 58, 45-65 (2011).
Westerink, J. R. Luettich, J. Feyen, J. Atkinson, C. Dawson, M. Powell, J. Dunion, H. Roberts, E. Kubatko, and H. Pourtaheri, 2006
Funder Acknowledgement(s): This study was supported by a HBCU-UP Research Initiative Award grant from NSF to Dr. Muhammad Akbar, Assistant Professor, Tennessee State University, 3500 John A. Merritt Blvd Nashville, TN 37209.
Faculty Advisor: Muhammad Akbar, firstname.lastname@example.org