Pathfinder
Editor, Senior Moderator
Comment: This report and study of hurricane Katrina are showing that the storm surge was the main killer during hurricane Katrina and size and history of a storm must be considered in predicting the storm surge heights .
Tropical Cyclone Report Hurricane Katrina
23-30 August 2005 Richard D. Knabb, Jamie R. Rhome, and Daniel P. Brown National Hurricane Center 20 December 2005 Updated 10 August 2006 for tropical wave history, storm surge, tornadoes, surface observations, fatalities, and damage cost estimates
Source: http://www.nhc.noaa.gov/pdf/TCR-AL122005_Katrina.pdf
Excerpt:
A precise measurement of the storm surge produced by Katrina along the northern Gulf coast has been complicated by many factors, including the widespread failures of tide gauges. Additionally, in many locations, most of the buildings along the coast were completely destroyed, leaving relatively few structures within which to identify still-water marks. Despite these challenges, several high water mark observations of the storm surge from along the Louisiana, Mississippi, and Alabama coasts were collected and analyzed under the direction of the Federal Emergency Management Agency (FEMA). These data indicate that the storm surge was about 24 to 28 ft along the Mississippi coast across a swath about 20 miles wide, centered roughly on St. Louis Bay. This area encompasses the eastern half of Hancock County and the western half of Harrison County and includes the communities of Waveland, Bay St. Louis, Pass Christian, and Long Beach. The maximum high water mark observation of storm surge was 27.8 ft at Pass Christian, on the immediate Gulf coast just east of St. Louis Bay. The data also indicate that the storm surge was 17 to 22 ft along the eastern half of the Mississippi coast, roughly from Gulfport to Pascagoula. The surge appears to have penetrated at least six miles inland in many portions of coastal Mississippi and up to 12 miles inland along bays and rivers. The surge crossed Interstate 10 in many locations. Observations also indicate Katrina produced a lesser but still very significant storm surge of 10 to 15 ft along coastal areas of western Alabama (Mobile County) including Dauphin Island. Katrina also caused flooding several miles inland from the Gulf coast along Mobile Bay where data indicate a storm surge of 8 to 12 ft occurred, in particular along the northern and western shores of the bay. Observations indicate that the storm surge along the Gulf coast of eastern Alabama (Baldwin County) was as high as about 10 ft.
Although the storm surge was highest to the east of the path of the eye of Katrina, a very significant storm surge also occurred west of the path of the eye. As the level of Lake Pontchartain rose, several feet of water were pushed into communities along its northeastern shore in St. Tammany Parish from Slidell to Mandeville, Louisiana. High water mark data indicate the storm surge was 12 to 16 ft in those areas. The data also indicate a storm surge of 15 to 19 ft occurred in eastern New Orleans, St. Bernard Parish, and Plaquemines Parish, while the surge was 10 to 14 ft in western New Orleans along the southern shores of Lake Pontchartrain.
Farther west, observations indicate a storm surge of 5 to 10 ft along the shores of western Lake Pontchartrain. The surge severely strained the levee system in the New Orleans area. Several of the levees and floodwalls were overtopped and/or breached at different times on the day of landfall. Most of the floodwall and levee breaches were due to erosion on the back side caused by overtopping, but a few breaches occurred before the waters reached the tops of the floodwalls. The surge overtopped large sections of the levees east of New Orleans, in Orleans Parish and St. Bernard Parish, and it also pushed water up the Intracoastal Waterway and into the Industrial Canal. The water rise in Lake Pontchartrain strained the floodwalls along the canals adjacent to its southern shore, including the 17th Street Canal and the London Avenue Canal. Breaches along the Industrial Canal east of downtown New Orleans, the London Avenue Canal north of downtown, and the 17th Street Canal northwest of downtown appear to have occurred during the early morning on 29 August. Overall, about 80% of the city of New Orleans flooded, to varying depths up to about 20 ft, within a day or so after landfall of the eye. Following the setbacks caused by additional flooding associated with the late September 2005 passage of Hurricane Rita to the south, the Army Corps of Engineers reported on 11 October 2005, 43 days after Katrina?s landfall, that all floodwaters had been removed from the city of New Orleans.
The massive storm surge produced by Katrina, even though it had weakened from Category 5 intensity the previous day to Category 3 at landfall in Louisiana, can be generally explained by the huge size of the storm. Katrina had on 29 August a large (about 25-30 n mi) radius of maximum winds and a very wide swath of hurricane force winds that extended at least 75 n mi to the east from the center. Even though Hurricane Camille (1969) was more intense than Katrina at landfall while following a similar track, Camille was far more compact and produced comparably high storm surge values along a much narrower swath. Also, Katrina had already generated large northward-propagating swells, leading to substantial wave setup along the northern Gulf coast, when it was at Category 4 and 5 strength during the 24 hours or so before landfall. In fact, buoy 42040, operated by the National Data Buoy Center (NDBC) and located about 64 n mi south of Dauphin Island, Alabama, reported a significant wave height (defined as the average of the one-third highest waves) of 30 ft as early as 0000 UTC 29 August. This buoy later measured a peak significant wave height of 55 ft at 1100 UTC that matches the largest significant wave height ever measured by a NDBC buoy. Overall, Katrina?s very high storm surge is attributable mainly to the large horizontal size of the hurricane, with the total water level being further increased by waves, including those generated the previous day when Katrina was at Category 5 strength.
...
Presumably, most of the deaths in Louisiana were directly caused by the widespread storm surge-induced flooding and its miserable aftermath in the New Orleans area. However, several indirect fatalities in Louisiana have been confirmed or are suspected, and some deaths included in the total might not be related to Katrina at all. Louisiana also reports that persons of more than 60 years of age constituted the majority of the Katrina-related fatalities among its residents. The vast majority of the fatalities in Mississippi probably were directly caused by the storm surge in the three coastal counties.
...
The storm surge of Katrina struck the Mississippi coastline with such ferocity that entire coastal communities were obliterated, some left with little more than the foundations upon which homes, businesses, government facilities, and other historical buildings once stood...
Study: Hurricane Katrina storm surge distribution and field observations
on the Mississippi Barrier Islands
Source: http://www.gtsav.gatech.edu/cee/groups/katrina/publications/ECSS_HurricaneKatrina_Fz.pdf
Excerpt:
5. Storm surge comparison between Hurricane Camille and Katrina
The similar tracks of Hurricane Katrina (Category 3 at landfall) and Camille (Category 5 at landfall) enable a direct comparison of the induced storm surges shown in Fig. 1. Both hurricanes moved at similar speeds of 20 km/h within the last 24 hours prior to the main landfall. The massive storm surge produced by Katrina is primarily attributed to the huge size of the storm. On 29 August, Katrina had a 50 km radius of maximum sustained winds and a very wide swath of hurricane force winds that extended 140 km (from the center toDauphin Island, AL). In addition Katrina had already generated large northward-propagating swells as a Category 5 storm in the hours before landfall, leading to substantial wave setup along the northern Gulf coast. Hurricane Camille (1969) was more intense than Katrina at landfall in terms of peak wind velocities. However Camille was far more compact, with hurricane force winds extending only 100 km to the east of the center resulting in a narrower storm surge distribution (ESSA, 1969). The 6.9 m maximum high water mark recorded in the aftermath of Hurricane Camille was likely exceeded in the Richelieu apartment complex in Pass Christian (MS) prior to their collapse, according to eyewitness estimates of 8.5 m (Hearn, 2004). Summarizing, Katrina?s high water levels were due to the size of the Category 3 storm enhanced by waves generated in the hours prior to landfall by a Category 5 strength storm. The comparison between the storm surges induced by Hurricanes Katrina and Camille illustrates that the storm surge is not solely determined by the wind velocity-based Saffire -Simpson scale. Several Camille survivors became victims misled by the assumption that their properties would not be inundated by the Category 3 Katrina storm surge since the Category 5 Camille storm surge spared them.
Even the house on Cat Island that survived Hurricane Camille in 1969 to record a storm surge height of 5 m, was completely destroyed by Hurricane Katrina?s storm surge (Fig. 3b). Hurricane Katrina?s storm surge exceeded Hurricane Camille?s at all survey locations.
6. Conclusion
The rapid response of the survey team led to the recovery of important ephemeral data on the characteristics of hurricane impact on large low-lying coastal plains and barrier islands particularly vulnerable to storm surge flooding. The systematic storm surge height measurements along the coastlines of Louisiana, Mississippi, Alabama and Florida resulted in a unique data set of 152 data points with 56 on the barrier islands, revealing both the onshore and offshore storm surge distribution. The peaks in the measured storm surge height distribution exceeded 10 m along the Mississippi coastline. At every survey location Hurricane Katrina?s storm surge (Category 3 at landfall) surpassed Hurricane Camille?s storm surge heights (Category 5 at landfall). The wind velocity-based Saffire -Simpson scale is limited in categorizing storm surge heights. The lower floors of specially designed buildings were damaged by the storm surge and storm wave impact, while the upper floors sustained minimal wind damage...
Tropical Cyclone Report Hurricane Katrina
23-30 August 2005 Richard D. Knabb, Jamie R. Rhome, and Daniel P. Brown National Hurricane Center 20 December 2005 Updated 10 August 2006 for tropical wave history, storm surge, tornadoes, surface observations, fatalities, and damage cost estimates
Source: http://www.nhc.noaa.gov/pdf/TCR-AL122005_Katrina.pdf
Excerpt:
A precise measurement of the storm surge produced by Katrina along the northern Gulf coast has been complicated by many factors, including the widespread failures of tide gauges. Additionally, in many locations, most of the buildings along the coast were completely destroyed, leaving relatively few structures within which to identify still-water marks. Despite these challenges, several high water mark observations of the storm surge from along the Louisiana, Mississippi, and Alabama coasts were collected and analyzed under the direction of the Federal Emergency Management Agency (FEMA). These data indicate that the storm surge was about 24 to 28 ft along the Mississippi coast across a swath about 20 miles wide, centered roughly on St. Louis Bay. This area encompasses the eastern half of Hancock County and the western half of Harrison County and includes the communities of Waveland, Bay St. Louis, Pass Christian, and Long Beach. The maximum high water mark observation of storm surge was 27.8 ft at Pass Christian, on the immediate Gulf coast just east of St. Louis Bay. The data also indicate that the storm surge was 17 to 22 ft along the eastern half of the Mississippi coast, roughly from Gulfport to Pascagoula. The surge appears to have penetrated at least six miles inland in many portions of coastal Mississippi and up to 12 miles inland along bays and rivers. The surge crossed Interstate 10 in many locations. Observations also indicate Katrina produced a lesser but still very significant storm surge of 10 to 15 ft along coastal areas of western Alabama (Mobile County) including Dauphin Island. Katrina also caused flooding several miles inland from the Gulf coast along Mobile Bay where data indicate a storm surge of 8 to 12 ft occurred, in particular along the northern and western shores of the bay. Observations indicate that the storm surge along the Gulf coast of eastern Alabama (Baldwin County) was as high as about 10 ft.
Although the storm surge was highest to the east of the path of the eye of Katrina, a very significant storm surge also occurred west of the path of the eye. As the level of Lake Pontchartain rose, several feet of water were pushed into communities along its northeastern shore in St. Tammany Parish from Slidell to Mandeville, Louisiana. High water mark data indicate the storm surge was 12 to 16 ft in those areas. The data also indicate a storm surge of 15 to 19 ft occurred in eastern New Orleans, St. Bernard Parish, and Plaquemines Parish, while the surge was 10 to 14 ft in western New Orleans along the southern shores of Lake Pontchartrain.
Farther west, observations indicate a storm surge of 5 to 10 ft along the shores of western Lake Pontchartrain. The surge severely strained the levee system in the New Orleans area. Several of the levees and floodwalls were overtopped and/or breached at different times on the day of landfall. Most of the floodwall and levee breaches were due to erosion on the back side caused by overtopping, but a few breaches occurred before the waters reached the tops of the floodwalls. The surge overtopped large sections of the levees east of New Orleans, in Orleans Parish and St. Bernard Parish, and it also pushed water up the Intracoastal Waterway and into the Industrial Canal. The water rise in Lake Pontchartrain strained the floodwalls along the canals adjacent to its southern shore, including the 17th Street Canal and the London Avenue Canal. Breaches along the Industrial Canal east of downtown New Orleans, the London Avenue Canal north of downtown, and the 17th Street Canal northwest of downtown appear to have occurred during the early morning on 29 August. Overall, about 80% of the city of New Orleans flooded, to varying depths up to about 20 ft, within a day or so after landfall of the eye. Following the setbacks caused by additional flooding associated with the late September 2005 passage of Hurricane Rita to the south, the Army Corps of Engineers reported on 11 October 2005, 43 days after Katrina?s landfall, that all floodwaters had been removed from the city of New Orleans.
The massive storm surge produced by Katrina, even though it had weakened from Category 5 intensity the previous day to Category 3 at landfall in Louisiana, can be generally explained by the huge size of the storm. Katrina had on 29 August a large (about 25-30 n mi) radius of maximum winds and a very wide swath of hurricane force winds that extended at least 75 n mi to the east from the center. Even though Hurricane Camille (1969) was more intense than Katrina at landfall while following a similar track, Camille was far more compact and produced comparably high storm surge values along a much narrower swath. Also, Katrina had already generated large northward-propagating swells, leading to substantial wave setup along the northern Gulf coast, when it was at Category 4 and 5 strength during the 24 hours or so before landfall. In fact, buoy 42040, operated by the National Data Buoy Center (NDBC) and located about 64 n mi south of Dauphin Island, Alabama, reported a significant wave height (defined as the average of the one-third highest waves) of 30 ft as early as 0000 UTC 29 August. This buoy later measured a peak significant wave height of 55 ft at 1100 UTC that matches the largest significant wave height ever measured by a NDBC buoy. Overall, Katrina?s very high storm surge is attributable mainly to the large horizontal size of the hurricane, with the total water level being further increased by waves, including those generated the previous day when Katrina was at Category 5 strength.
...
Presumably, most of the deaths in Louisiana were directly caused by the widespread storm surge-induced flooding and its miserable aftermath in the New Orleans area. However, several indirect fatalities in Louisiana have been confirmed or are suspected, and some deaths included in the total might not be related to Katrina at all. Louisiana also reports that persons of more than 60 years of age constituted the majority of the Katrina-related fatalities among its residents. The vast majority of the fatalities in Mississippi probably were directly caused by the storm surge in the three coastal counties.
...
The storm surge of Katrina struck the Mississippi coastline with such ferocity that entire coastal communities were obliterated, some left with little more than the foundations upon which homes, businesses, government facilities, and other historical buildings once stood...
Study: Hurricane Katrina storm surge distribution and field observations
on the Mississippi Barrier Islands
Source: http://www.gtsav.gatech.edu/cee/groups/katrina/publications/ECSS_HurricaneKatrina_Fz.pdf
Excerpt:
5. Storm surge comparison between Hurricane Camille and Katrina
The similar tracks of Hurricane Katrina (Category 3 at landfall) and Camille (Category 5 at landfall) enable a direct comparison of the induced storm surges shown in Fig. 1. Both hurricanes moved at similar speeds of 20 km/h within the last 24 hours prior to the main landfall. The massive storm surge produced by Katrina is primarily attributed to the huge size of the storm. On 29 August, Katrina had a 50 km radius of maximum sustained winds and a very wide swath of hurricane force winds that extended 140 km (from the center toDauphin Island, AL). In addition Katrina had already generated large northward-propagating swells as a Category 5 storm in the hours before landfall, leading to substantial wave setup along the northern Gulf coast. Hurricane Camille (1969) was more intense than Katrina at landfall in terms of peak wind velocities. However Camille was far more compact, with hurricane force winds extending only 100 km to the east of the center resulting in a narrower storm surge distribution (ESSA, 1969). The 6.9 m maximum high water mark recorded in the aftermath of Hurricane Camille was likely exceeded in the Richelieu apartment complex in Pass Christian (MS) prior to their collapse, according to eyewitness estimates of 8.5 m (Hearn, 2004). Summarizing, Katrina?s high water levels were due to the size of the Category 3 storm enhanced by waves generated in the hours prior to landfall by a Category 5 strength storm. The comparison between the storm surges induced by Hurricanes Katrina and Camille illustrates that the storm surge is not solely determined by the wind velocity-based Saffire -Simpson scale. Several Camille survivors became victims misled by the assumption that their properties would not be inundated by the Category 3 Katrina storm surge since the Category 5 Camille storm surge spared them.
Even the house on Cat Island that survived Hurricane Camille in 1969 to record a storm surge height of 5 m, was completely destroyed by Hurricane Katrina?s storm surge (Fig. 3b). Hurricane Katrina?s storm surge exceeded Hurricane Camille?s at all survey locations.
6. Conclusion
The rapid response of the survey team led to the recovery of important ephemeral data on the characteristics of hurricane impact on large low-lying coastal plains and barrier islands particularly vulnerable to storm surge flooding. The systematic storm surge height measurements along the coastlines of Louisiana, Mississippi, Alabama and Florida resulted in a unique data set of 152 data points with 56 on the barrier islands, revealing both the onshore and offshore storm surge distribution. The peaks in the measured storm surge height distribution exceeded 10 m along the Mississippi coastline. At every survey location Hurricane Katrina?s storm surge (Category 3 at landfall) surpassed Hurricane Camille?s storm surge heights (Category 5 at landfall). The wind velocity-based Saffire -Simpson scale is limited in categorizing storm surge heights. The lower floors of specially designed buildings were damaged by the storm surge and storm wave impact, while the upper floors sustained minimal wind damage...