Storm Surge: Physical Processes and an Impact Scale

Abstract

Tropical cyclone-generated storm surges create natural disasters that are among the most deadly and costly global catastrophes. Individual disasters have inflicted hundreds of thousands of fatalities and billions of dollars in damage. In 1970, a tropical cyclone in the Bay of Bengal generated a 9.1-meter surge which killed approximately 300,000 people in Bangladesh (Frank and Husain 1971; Dube et al. 1997; De et al. 2005). More recently, and well into the age of satellite meteorology, a storm surge in 1991 killed approximately 140,000 people in Bangladesh (Dube et al. 1997). Although the magnitude of storm surge heights and loss of life are highest along the shores of Bangladesh and India, such disasters are not limited to countries with developing economies. The 1900 Galveston Hurricane generated a 6.1-meter surge (Garriott 1900), which killed between 6,000 and 8,000 people in Galveston, Texas (Rappaport and Fernandez-Partagas 1995), producing the most deadly natural disaster in United States history (National Oceanic and Atmospheric Administration 1999). More recently, Hurricane Katrina (2005) generated an 8.47-meter surge (Knabb et al. 2006), which claimed more than 1,800 lives along the coasts of Louisiana and Mississippi, and inflicted $81 billion dollars in damage (McTaggart-Cowan et al. 2008). While tropical cyclone-generated storm surge is a deadly and costly hazard, it is also scientifically complex, because meteorological, oceanographic and geographic factors influence the height, extent and duration of storm surge flooding. Such factors include maximum sustained hurricane wind speed at landfall and offshore, hurricane size, hurricane forward speed, the angle of hurricane approach to the coastline, bathymetry of coastal waters, coastline shape and the presence of barriers or obstructions to surge waters on land. Although relationships between some of these factors and resultant surge heights may seem intuitive (e.g. the assumption that stronger hurricanes always generate higher surges), storm surge observations reveal that a combination of physical factors influence surge characteristics. As a result, weaker hurricanes sometimes generate higher surges than stronger hurricanes. For example, Hurricane Ike (2008) generated a 5.33-meter surge along the Upper Texas Coast, although maximum sustained winds at landfall were only 175 km/ hour (Berg 2009), whereas Hurricane Charley in Western Florida had maximum sustained winds of 240 km/ hour at landfall, but only generated a 2.13-meter surge, partly because the storm rapidly intensified just before making landfall (Pasch et al. 2004). The complex nature of storm surge makes this phenomenon difficult to forecast and difficult for coastal populations to understand. In cases where storm surge heights and extents are