David R. Basco, Nader Mahmoudpour


A coastal storm-strength parameter, the Coastal Storm Impulse (COSI) parameter was introduced at the ICCE 2006 (San Diego) and further discussed in the ICCE 2008 (Hamburg) and ICCE 2010 (Shanghai) proceedings. COSI is based on the conservation of linear, horizontal momentum to combine storm surge, wave dynamics, and currents over the storm duration. Both tropical storms (hurricanes) and extra-tropical storms (low-pressure fronts) can produce similar COSI parameters. Analysis of coastal storms over a 10 year period (1994-2003) of measured data at the Corps of Engineers, Field Research Facility (FRF), Duck, NC showed the need to modify the original method to (1) use the mean, nonlinear wave momentum flux, and (2) use only the spikes in storm surge when elevated water levels are above the mean high water level of the tide. This paper presents the full details of how to calculate the modified COSI parameter; the modified results for the 10-yr Duck data set and suggest possible applications to develop fragility curves for coastal engineering design. Clearly, fragility curves are needed to quantify risk and hence resilience in coastal systems design. The intensity of the “load” or “disturbance”, i.e. the severity of the coastal storm must be quantified to develop fragility curves. Excess water levels (storm surge), wave conditions (height, period, direction) and storm duration all contribute to the intensity of a coastal storm. How to combine these three factors has long been a concern of coastal scientists and engineers.


coastal storms; storm surge; wave height; storm duration; momentum; storm impulses; storm-strength parameter; fragility curves

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Basco, D.R., and C. Klentzman, 2006. On the Classification of Coastal Storms Using Principles of Momentum Conservation, Proceedings, ICCE 2006, San Diego, ASCE, NY, Vol. 2, pp. 1407-1419.

Basco, D.R., N. Mahmoudpour and C. Klentzman. 2008. Statistical Analysis of the Coastal Storm Impulse, (COSI) Scale at the Corps of Engineers, FRF, Duck NC, Proceedings, ICCE 2008, Hamburg, ASCE, NY, Vol. 6, 4134-4142.

Basco, D.R. and R. Walker 2010 "Application of the Coastal Storm Impulsse (COSI) Parameter to Predict Coastal Erosioin" Proceedings, ICCE 2010, Shanghai, ASCE, NY, Vol. pp.

Dolan, R and R.E. Davis, 1992 "An Intensity Scale for Atlantic Coast Northeast Storms" Jour. Coastal Research, Fort Lauderdale, FL, Vol 8, No.4 pp 840-853.

Dolan, R, Hayden, D., Bosserman, K., Lisle, L. 1987. Frequency and Magnitude Data on Coastal Storms, Journal of Coastal Research, vol. 3, no. 2. Charlottesville, VA, pp. 245-247.

Dolan, R., Lins, H., and Hayden, B. 1988. Mid-Atlantic Coastal Storms, Journal of Coastal Research, vol. 4 no. 3. Charlottesville, VA, pp. 417-433.

Fenton, J.D. (1990) "Nonlinear Wave Theories", in The Sea- Ocean Engineering Science, LeMehaute and Hanes (Eds), vol 9, Wiley, NY, 3-25.

Gravens, M.B., Males, R.M., and D.A. Moser (2007) " Beach-fx: Monte Carlo Life-Cycle Simulation Model for Estimating Shore Protection Project Evolution and Cost Benefit Analyses", Shore & Beach, Vol 75, No. 1, 12-19.

Hughes, S.A. 2004. Wave Momentum Flux Parameter: a Descriptor for Near Shore Waves, Coastal Engineering, vol. 51. Elsevier, pp. 1067-1084.

Kamphuis, W. 2010. Introduction to Coastal Engineering and Management, World Scientific, Inc., NJ, 2nd Edition.

Klentzman, C. 2007. Using Principles of Momentum Conservation to Develop Coastal Strom Impulse Scale (COSI), Unpublished, Ph.D. Dissertation, Old Dominion University, Norfolk, VA.

Longuet-Higgins, M.S. and R.W. Stewart, 1964 "Radiation Stresses in Water Waves: A Physical Discussion With Applications", Deep-Sea Research, Vol 11, Pergamon Press, UK, pp 529-562.

Mahmoudpour, N (2012) "The Modified Coastal Storm Impulse Parameter", unpublished, PhD Dissertation, Civil Engineering Department, Old Dominion University, Norfolk, VA

Miller, J.K., Livermont, E. 2008. A Predictive Index for Wave and Storm Surge Induced Erosion, Proceedings, 31st Coastal Engineering Conference, ASCE, NY, pp 561-572.

Munger, S., and Kraus, N.C. 2010. Frequency of Extreme Storms Based on Beach Erosion at Northern Assateague Island, Maryland, Shore & Beach, Vol.78, No.2. pp. 3-11.Seymour, R.J., Strange, R.R., III, Cayan, R., Nathan, R.A. 1984. Influence of El Ninos on California's Wave Climate, Proceedings, 19th International Conf. on Coastal Engineering, ASCE, NY, Vol 1, pp 577-592.

Schultz, M.T., S. K. McKay, and L. Z. Hales (2011) "The Quantification and Evolution of Resilience inIntegrated Coastal Systems, ERDC-TR-11-XX (Draft), Vicksburg, MS, US Army Corps of Engineers

Schultz, M.T., B.P. Gouldby, J.D. Simm, and J.L. Wibowo (2010) "Beyond the Factor of Safety: Developing Fragility Curves to Characterize System Reliability, ERDC-SR-10-1, Vicksburg, MS, US Army Corps of Engineers

Sobey, R.J. (1990) "Wave Theory Predictions af Crest Kinematics" in Water Wave Kinematics, Torum and Gudmestad (Eds), Klumer Academic Public, the Netherlands, 215-231

Sobey, R.J.,et al (1998) FORTRAN CODE for Fourier Wave Theory, University of California, Berkeley,

You, Z.-J. and Lord, D. 2008. Influence of the El Nino-Southern Oscillation on NSW Coastal Storm Severity, Journal of Coastal Research, vol 24 Sp No.2, pp203-207.