Extreme Coastal Waves, Ocean Surges and Wave Runup

Abstract

Extreme coastal waves together with elevated water levels due to storm surges and wave runup often cause damage to coastal property and infrastructure, erode sandy beaches and dunes, inundate coastal and estuarine lands, and gradually degrade coastal ecosystems. Knowledge of extreme waves and elevated water levels is essential for coastal and offshore structure designs, coastal development planning, shore protection measures, and coastal port operations. Estimates of extreme coastal waves and elevated water levels are also required by almost all coastal engineering studies. The purpose of this book chapter is to provide coastal engineers/scientists with basic theories and practical methodologies for estimation of extreme coastal waves, storm surges and wave runup. For the completeness of this chapter, short-term wave analysis is also presented to determine coastal wave statistics. A zero-crossing wave power spectrum is developed to explain the discrepancy between significant wave heights calculated from the zero-crossing method and from the zero-th moment of the wave spectrum. Long-term wave analysis is then presented to extrapolate historical wave records to extreme wave heights, and the uncertainty in estimates of extreme wave heights is also discussed in detail. Oceanic surges driven by both wind field and low atmospheric pressure system are estimated, and an analytical solution is also presented to describe the growth of a wind-driven surge. Finally, semi-empirical formulas are proposed to calculate regular wave runup, irregular wave runup, and extreme wave runup on coastal sandy beaches.