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Sensitivity Matrix

I(b) Waves and Storm Surge - Additional Detail

Asset Categories   Waves and Storm Surge - Additional Detail
Mode Sub-Mode Important Impact-Asset Relationships Threshold Mobile-Specific Detail
Bridges Bridge (Superstructure) Most bridges damaged during Katrina were near water, with most damage occurring to the bridge superstructure. Both Douglass et al (2008) and Padgett et al. (2009) hypothesize that the connection between the bridge's superstructure and substructure and other engineering design decisions can influence the extent of damage experienced by the bridge. [21, 51] Chen et al. (2009) recommend using the crest elevation of the average of the highest 1/3 of the storm waves riding on the peak surge relative to the low chord elevation of the bridge as the threshold for identifying vulnerability. [13] High Damage Levels: The combination of intense storm surge, winds, and wave activity can unseat multiple bridge spans and necessitate replacing the entire bridge. Repair expenses includes the cost of demolishing and removing the destroyed bridge, the cost of the new bridge, and the cost of creating alternative modes of transport while the bridge is being repaired. For example, Hurricane Frederic caused $37 million worth of damage to the Dauphin Island Bridge in 1979 with a 13 foot storm surge, not including the cost of the ferry service and other services to connect the Dauphin Island residents with needed supplies. [59]
Moderate Damage Levels: Moderate damage includes degradation of columns (including cracking and spalling), abutment scour, damage to submerged electronic equipment, and damage to guardrails. For example, in 2004 Hurricane Katrina caused moderate damage to the Dauphin Island Causeway through bridge scour and debris impacts. [50, 51]
Slight Damage Levels: Examples of slight damage include minor cracking and spalling to the abutment, minor spalling at the column, and minor cracking at the deck. Minor damage is often due to wind (i.e. wind pulling off the roofs of operator houses), rather than storm surge. Slightly damaged bridges tend to have repair costs of under $10,000. [50, 51]
Bridge (Substructure) Flood-related and long-term erosion can increase Base Flood Elevation (BFE) and wave heights, resulting in increased inundation and wave-related damage to buildings and structures. BFE is the computed elevation to which floodwater is expected to reach during a 100-year flood event. [69] Erosion (E) zones, or coastal areas that experience significant flood-related and long-term erosion are not currently included in flood maps, but long-term erosion is measured by state and federal government agencies. [68]
Operator Houses (movable bridges) and electrical parts Even when repairs to bridge are made quickly, commercial power might not be available until some time after the storm. [47] FHWA's Federal-Aid Policy Guide (1994) Section 650.809 recommends that a fixed bridge be selected wherever practicable. Therefore, if damage to the bridge is so severe that the entire bridge must be replaced, rebuilding might require building a more expensive, but safer, fixed bridge in place of the movable bridge.
Roads and Highways Paved road surface There is evidence that the "weir" water flow pattern might often be the primary failure mode (i.e. during Hurricanes Ivan and Katrina). For example, during Hurricane Katrina, the majority of the damage occurred on the north side of roads which are parallel to the coast and also elevated compared to the adjacent road shoulder. Damage to road pavement during Hurricane Ivan also tended to occur on the landward side of the coastal road, indicating that the "weir" effect may have been the primary cause of failure. [63]   During Hurricane Frederic, road damage on Dauphin Island was estimated at $900,000. The main east-west road (Bienville Boulevard) was covered with 3 feet of sand on the western end, which may have helped to protect it from the storm surge since the road had only minor damage once the sand was removed. However, about 80% of the roads on the western side of the island and about 20% of the roads on the eastern side of the island were damaged. [59]
Road substructure (gravel base, substructure)   During Hurricanes Katrina and Rita, highway pavement damage occurred on sections of US-90 (buckled or dropped into sinkholes), US-82 (pavement scour where the road had little protection from the storm surge), and other highways. [47, 22]
Unpaved roads      
Stormwater drainage (culverts, side drains, etc)      
Highway, road and street signs and traffic lights      
Highway and road traffic and service      
Railroads Electrical Equipment (gates/flashers and signal bungalows)     The CSX bridge had its railroad tracks and ties completely washed off by wave forces, but the superstructure remained largely intact and connected to the supporting bridge piers.
Railroad Tracks, Ties, and Ballast    
Railroad services (i.e., operations)    
Airports/ Heliports Runway and navigational aids     Mobile Downtown Airport: runway has an elevation of 26 ft above sea level, slightly above the threshold of a 7 m (23 ft) storm surge. According to the U.S. Climate Change Science Program's Gulf Coast Phase I report, Mobile Downtown Airport's elevation is 5.8 m (19 ft), so portions of the airport may be exposed to 7 m storm surges.
Mobile Regional Airport: Airport has an elevation of 219 ft. above sea level and it is located inland, so it is not susceptible to flooding from storm surges
Dauphin Island Airport: Runway is at an elevation of 5 ft. above sea level, exposing it to storm surges from 0 to 5.5 m (0 to 18 ft) and higher.
St. Elmo Airport: Airport has an elevation of 133 ft. above sea level, and it is located inland, so it is not exposed to flooding from storm surges.
Airfield buildings and structures (e.g., terminal buildings, hangers, air traffic control tower)    
Services and airport/ heliport operations (e.g., flight departures and arrivals, baggage/cargo transfers, ground transportation)    
Natural Oil and Gas Pipelines Pipelines, aboveground Storm surge has not had much impact on onshore transmission pipelines historically, although Hurricanes Andrew, Ivan, and Katrina caused extensive damage to pipelines, particularly underwater pipelines. [60]    
Pipelines, underground Storm surge has not had much impact on onshore transmission pipelines historically, although Hurricanes Andrew, Ivan, and Katrina caused extensive damage to pipelines, particularly underwater pipelines. [60]   During Hurricane Katrina, there was some damage to natural gas regulator stations. [47]
Pipelines, offshore Wave action can expose and damage offshore pipelines, causing vertical movement or rupture. Wave action may affect the seabed by destabilizing the sand or silt above buried offshore pipelines. [49, 60] During Hurricanes Katrina and Rita, platform damage was responsible for 43% of all reported damages. 17% of the damage reports were associated with a submerged pipe. [71] Studies of Hurricanes Andrew, Lili, Ivan, Katrina, and Rita off of the Gulf Coast have found that the majority of failures occur in water depths less than 200 feet. [71]
- Studies have found that the age of the pipe does not have an affect on likelihood of damage. [71]
Aboveground infrastructure (e.g., compressor stations, metering stations, other buildings, structures)      
Utilities for pipelines - electricity      
Electric Power Systems Electric Power Systems Electricity powers critical elements of nearly all transportation modes. For example, traffic lights and signs, railroad signal systems and crossing gates, port cranes and elevators, and pipeline pumping stations all require electricity. [33, 47]   During Hurricane Katrina, electrical power outages caused the shutdown of ports, railroads, refineries, and pipeline stations that were otherwise not badly damaged during the storm. Power outages were the number one reason for delay in resuming transportation services in the Gulf Coast region. [33]
Marine Ports, Terminals, and Waterways Electrical Equipment      
Terminal Buildings While the velocity of the storm surge flow is also likely to impact buildings, modeling indicates that storm surge and wave action are more powerful causes of damage to buildings than flood velocity. [44]   Hurricane Frederic destroyed one cargo warehouse and damaged 24 other warehouses as well as 71 smaller buildings. At the Alabama State Docks, two bulk material unloading cranes were destroyed, and two heavy cargo cranes were damaged. Hurricane Frederic also damaged four conveyors at the bulk material handling plant and grain elevator structures. [59]
Channels Blocking of channels from additional debris/sediment. [48]   During Hurricane Frederic, the "Nordic Texas", a 623 foot long tanker was under repair at the Alabama Dry Docks and Shipbuilding Company. The tanker was washed into the Mobile River as a result of high storm surge and strong wind. In addition, clean up crews had to remove eight sunken barges from the Mobile Shipping Channel. [59]
Piers, wharves, and berths   To reduce damage from waves, pier deck elevations should be located above the highest expected wave crest elevation. [32]  
Port services (i.e., operations) After Hurricane Katrina, the two largest impediments to completely re-opening the ports affected in Louisiana were lack of electricity and lack of workers (workers were without housing following the storm). Another important impact was the temporary closure of certain shipping channels while debris was being cleared. [17, 30]   During Hurricane Frederic, companies with marine facilities along the Mobile River had to repair damages to drydocks, piers, bulkheads, and wharves. At Dauphin Island, nearly all of the recreational boats at the marina were destroyed during the storm. [31, 59]

*Note dollar amounts are not adjusted for inflation.

Updated: 03/27/2014
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