HURRICANE ELENA DAMAGE SURVEY: SEPTEMBER 2, 1985by Timothy P. Marshall (September 1985)
We have completed a damage investigation of Gulf Coast areas struck by Hurricane Elena. In particular, the degree of structural damage caused by wind and wave effects was documented. Meteorology data were gathered and summarized in this report.
GENERAL WEATHER BACKGROUND
Hurricane Elena originated from a tropical depression which had traveled westward over the Atlantic Ocean during the last week in August 1985. The storm reached tropical storm status and was given the name Elena at noon (CDT) on August 28, 1985. Elena rapidly grew in intensity and size reaching hurricane status at 6 a.m. the next morning.
The forward speed of the hurricane was close to 30 mph to the west-northwest direction on August 29, 1985. Landfall appeared imminent near Gulfport, MS the next day. However, during the next twenty-four hours Elena slowed in translation and began turning east toward the Florida Peninsula. The eye of Hurricane Elena remained essentially stationary off the Florida coast near the town of Cedar Key on August 31, 1985. The storm system continued to intensify throughout the day with reconnaissance wind speed estimates increasing from 75 to 125 mph in the eye wall.
Around noon (CDT) on September 1, 1985, Hurricane Elena began moving in a steady west-northwest direction. Elena was now a major hurricane and was classified as a category 3 storm. The eye of Elena passed within 40 miles of Appalachicola, Florida and continued to parallel the Florida Peninsula that evening.
Hurricane Elena came ashore at 7 am (CDT) on September 2, 1985 near Biloxi, MI. Highest recorded wind speeds were 122 mph on Dauphin Island, AL. Highest storm surge was estimated around 10 feet in the Pascagoula, MI area. Lowest sea level pressure was 951 mb. The eye of the hurricane was about 20 miles in diameter at landfall. There were no confirmed tornadoes from the Florida Peninsula to Louisiana. A few tornadoes were confirmed in central Florida near Leesburg.
WIND DAMAGE ASSESSMENT
Wind damage was most severe along coastal and bayfront regions where wind fetch was long and unobstructed. Towns on the east side of the eye wall had the most intense damage from wind. These areas include Dauphin Island, AL, and the area between Pascagoula and Ocean Springs, MI. Wind speed/damage correlation revealed that maximum wind speeds in these areas were most likely between 100 and 120 mph. Residences generally had roof damage, roof loss to exterior wall loss. Several mobile homes, even with frame anchors, had rolled or disintegrated. Several shopping centers along Route 90 in Pascagoula had masonry wall failures and roofs collapsed.
Wind damage decreased rapidly away from the coastal areas. Minor wind damage such as loss of roof shingles, cladding and tree impact damage occurred west and north of Pass Christian, MI and east and north of Gulf Shores, AL. Wind speed/ damage correlation revealed maximum wind speeds were less than 100 mph along coastal areas and less than 80 mph inland.
Figure 1 illustrates the general categories of wind damage for the affected Gulf Coast region. Three categories for structural damage are minor, major, and considerable.
Maximum wind velocities were obtained from a variety of sources. These data are tabulated below. It is important to recognize that the location and height of these anemometers is not yet known and that these parameters may effect the magnitude of the wind speed.
LOCATION/ CDT MONTH/ MAXIMUM PEAK WIND
OBSERVER TIME DAY SUSTAINED GUST DIRECTION
New Orleans, 8:48 am 9/2 -- 28 mph --
Slidell,LA 10:15 am 9/2 30 mph 51 mph SW
Gulfport, MI 8:00 am 9/2 60 mph 105 mph --
Biloxi, MI morning 9/2 92 mph 115 mph --
Pascagoula, 5:00 am 9/2 92 mph 115 mph --
Mobile, AL 4:20 am 9/2 54 mph 60 mph SE
Dauphin Is.,AL 3:08 am 9/2 98 mph 122 mph --
Pensacola, FL 2:25 am 9/2 50 mph 92 mph E
Pensacola, FL morning 9/2 -- 81 mph E
Naval Air St.
Ft Walton Bch, 8:00 pm 9/1 -- 67 mph NE
FL, Eglin AFB
Panama City,FL 6:00 pm 9/1 -- 71 mph NE
Apalachicola, 4:40 pm 9/1 45 mph 68 mph NE
Carrabelle,FL evening 9/1 60 mph 95 mph --
Tallahassee, 5:10 pm 9/1 29 mph 44 mph E
Cedar Key,FL 3:30 pm 8/31 45 mph 60 mph S
Clearwater 7:30 am 8/31 -- 69 mph --
Tampa, FL 2:42 pm 8/31 31 mph 45 mph S
HIGH WATER MARKS
Within days after Elena made landfall, we determined the height above sea level of debris lines and watermarks along the Mississippi, Alabama, and Florida Coastline. The elevations were determined using an engineering transit and benchmark information given on U.S. Geological Survey maps.
A total of 30 watermark elevations were obtained. These data are listed below and are illustrated in Figure 2. Highest debris lines of 9 to 10 feet MSL were observed in Apalachicola, FL, Gulf Shores, AL and Pascagoula, MI area. Barrier islands in close proximity to the eye became submerged during the hurricane. Most of Dauphin Island was inundated.
We believe that the debris lines approximate the height of the storm surge. However, we recognize that many factors such as wave runup and beach topography can cause local variations in the debris line.
The storm surge was relatively small since Elena had paralleled the coastline minimizing the effectiveness of the coastline, bays and estuaries as a barrier for water to be pushed into. No doubt the storm surge and debris lines would have been higher had Elena come directly into the coastline.
NO. LOCATION WATER HEIGHT DESCRIPTION OF
AB0VE MSL MEASUREMENT
1 Waveland, MI. 3.3 Transit to debris
Rt 90 east of Bridge line, road 8 ft.
2 Henderson Point, MI 4.9 Transit to debris
Rt 90 west of Bridge line, road 8 ft.
3 Long Beach, MI 7.4 Transit to debris
Rt 90- oceanside line, BM 9 ft.
4 Biloxi, MI-West 8.0 Over the road debris
Route 90- oceanside at 8 ft.
5 Biloxi, MI 10.5 Transit to debris
Rt 90 and east bridge line, BM 13 ft.
6 Pascagoula, MI 8.5 Transit to debris
Beach Blvd and 4th St. line, road 6 ft.
7 Pascagoula, MI 6.0 Transit to debris
Bayou Casotte line, road 8 ft.
8 Bayou La Batre, AL 6.0 Over the road debris
Beach road- oceanside at 6 ft.
9 Heron Bay, AL 4.7 Transit to debris
Route 188 line, road 20 ft.
10 Mobile, AL- mouth 3.8 Obtained from the
of Mobile River Mobile NWS.
11 Point Clear, AL 5.0 Transit to debris
Mullet Point Rt 98 line, BM 4 ft.
12 Dauphin Island, AL 5.6 Transit to debris
Beach Road- bayside line, BM 4 ft.
13 Gulf Shores, AL 8.0 Over the road debris
Rt 182 at 8 ft.
14 Gulf Shores, AL- East 10.0 Transit to debris
Rt 182- oceanside line, road 11.6 ft.
15 Perdido Bay, AL 6.3 Transit to debris
Bridge on Rt 182 line, road 21 ft.
16 Pensacola Bay, FL 7.0 Transit to debris
Bridge on Rt 98 line, BM 15 ft.
17 Oriole Beach, FL 9.0 Transit to debris
Rt 399- oceanside line, road 11 ft.
18 Navarre, FL- Santa 6.0 Transit to debris
Rosa Sound on Rt 399 line, BM 28 ft.
19 Fort Walton Beach, FL 3.0 Transit to debris
Santa Rosa Sound, Rt 98 line, BM 4 ft.
20 Panama City Beach, FL 5.9 Transit to debris
Alt Rt 98- oceanside line, road 9 ft.
21 Mexico Beach, FL 8.5 Transit to debris
Rt 98- oceanside line, BM 12.7 ft.
22 Port St. Joe, FL 4.0 Transit to debris
Rt 98- in bay line, BM 16.8 ft.
23 Money Beach, FL 9.6 Transit to debris
Rt 3022- oceanside line, BM 8.6 ft.
24 Apalachicola, FL 9.0 Debris just below
Rt 98 bridge road at 11 ft.
25 Panacea, FL ___ Over the road debris
Rt 98 bridge at __ ft.
26 Cedar Key, FL ___ Over the road debris
Rt 24 bridge at __ ft.
27 Madeira Beach, FL ___ Over the road debris
Rt 699 at __ ft.
28 Treasure Island, FL ___ Over the road debris
Rt 699 at __ ft.
29 Johns Pass, FL 6.5 Transit to debris
Rt 699 and bridge line, BM 11.7 ft.
30 Tampa Bay, FL 7.7 Transit to debris
Rt 275 bridge line, BM 10.6 ft.
PHOTOGRAPHIC SURVEY OF DAMAGES
As Hurricane Elena was making landfall in Biloxi, MI, Haag Engineers were already on the scene conducting a damage survey westward from Fort Walton Beach, FL. The survey entailed documenting wind and wave damage to structures along the coastline before cleanup began. The damage survey was concluded at Pass Christian, MI by the end of the day. Over 300 photographs were taken. Structural performance of residences, mobile homes and commercial businesses were documented.
A few photographs highlighting the type of damages to structures in Hurricane Elena are appended. Photographs were assembled by state: Mississippi, Alabama, or Florida.
The storm damage and storm surge survey was completed within ten days after Hurricane Elena made landfall. Most coastal areas were investigated from Waveland, MI to Tampa, FL. Among the cities covered in the damage investigation were Waveland, Pass Christian, Gulfport, Biloxi, and Pascagoula, in Mississippi, Bayou La Batre, Dauphin Island and Gulf Shores, in Alabama, and Pensacola, Fort Walton Beach, Panama City, Apalachicola and St. Petersburg Beach in Florida.
It was immediately recognized that most of the wind damage was confined to the Mississippi coastline and barrier islands of Alabama. Pascagoula, MI and Dauphin Island, AL appeared to receive the highest wind speeds in Hurricane Elena due to the extent of roof damage to buildings. Maximum wind velocities appeared to exceed 100 mph at roof elevations. Wind speeds appeared to decrease rapidly inland and with further distance along the coast from the Hurricane Elena eye.
Wave damage to structures was most noticeable on the coastal areas of Alabama. Beachfront structures elevated on piers were undermined several feet on Dauphin Island and Gulf Shores, Alabama. A few structures built on grade had apparently floated. Beachfront pools in front of some condominiums in Gulf Shores were destroyed.