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Sensitivity Matrix

III(b) Precipitation - Additional Detail

Asset Categories   Precipitation - Additional Detail
Mode Sub-Mode Important Impact-Asset Relationships Threshold Mobile-Specific Detail
Bridges Bridge (Superstructure)      
Bridge (Substructure)
Operator Houses (movable bridges) and electrical parts
Roads and Highways Paved road surface The sensitivity of pavements depends on the type of pavement design. In Mobile County, most county roads are thin bituminous pavements, which are more sensitive to water than other types since if moisture breaches the subgrade from the pavement shoulder, it deforms the subgrade which is then subjected to high stress loads during traffic . In thick bituminous pavements, the thicker pavement layers mean that less stress is transmitted to the subgrade and the pavement is less sensitive to moisture in the subgrade. However, over time changes in temperatures and high traffic loads cause thick bituminous pavements to crack. Precipitation then accelerates the cracking damage.

Some of the common damage from moisture includes: surface defects, surface deformations, and cracking. A normal rain event is not enough to cause damage. However, if the pavement is completely submerged the water may begin to infiltrate the subgrade. If this happens multiple times, it will damage the pavement, particularly if the road has high traffic loads as well. [18]
County paved roads begin to experience damage at around a 50-100 year storm. Mobile County roads begin to experience flooding at around a 50 year storm, but may not require repair at that point. Mobile County does not track maintenance of roads after heavy rain events, therefore it is hard to determine the possible relationship between repairs and precipitation. [43] In Mobile County, roadways and structures that overtop during heavy rain events are usually located near streams. County engineers have identified roads that are prone to flooding. [43]
Road substructure (gravel base, substructure)      
unpaved roads Heavy rains can wash out unpaved roads easily.    
Stormwater drainage (culverts, side drains, etc) Stormwater run-off from roads and highways can accumulate pollutants such as "heavy metals from tires, brakes, and engine wear, and hydrocarbons from lubricating fluids". If not properly managed, run-off can degrade local water quality. [70] Debris from strong winds can greatly exacerbate damage caused by overflowing culverts.  
Highway, road and street signs and traffic lights      
Highway and road traffic and service   Drivers tend to drive more slowly during precipitation, reducing overall highway and road capacity. Evidence suggests that any level of rain increases risk of vehicle accidents, particularly at night.  
Railroads Electrical Equipment (gates/flashers and signal bungalows) More flooding from either freshwater or seawater.    
Railroad Tracks, Ties, and Ballast Flooding weakens/ softens wood. Flooding can weather/ erode ballast materials (soils and rock).    
Railroad services (i.e., operations) Rail service limited in cases of inundated tracks.    
Airports/ Heliports Runway and navigational aids Wet conditions can alter the limits imposed on aircraft take-off and landing operations, particularly alongside other climate conditions such as high wind, hail, lightning, freezing rain, snow.
Delays are caused by standing water on the tarmac, slowing vehicular movement on the airfield.
Wet runways can have lower crosswind take-off and landing limits. See "Wind" section for further details.  
Aircraft Freezing precipitation can cause icing that affects aircraft lift and other aerodynamic performance features. Hail greater than 1 inch in diameter can "severely damage" aircraft that are not in flight.  
Airfield buildings and structures (e.g., terminal buildings, hangers, air traffic control tower) Delays are caused by standing water on the tarmac, slowing vehicular movement on airfield, risk of injury to personnel or equipment.    
Services and airport/ heliport operations (e.g., flight departures and arrivals, baggage/cargo transfers, ground transportation) Delays may be caused by standing water on the tarmac, slowing vehicular movement on airfield, impeding construction projects, foot traffic, risk of injury to personnel or equipment. Delay can affect flight departures, construction projects, maintenance activities, general aircraft servicing (cleaning, catering, minor maintenance), and baggage/cargo transfer. Heavy rain causes standing water to form on the tarmac.
Wet runways can have lower crosswind take-off and landing limits. See "Wind" section for further detail.
 
Natural Oil and Gas Pipelines Pipelines, aboveground Increases in precipitation (both long-term or droughts/inundation from severe storms) could impact soil structure.
Intense precipitation can erode soil cover and cause subsidence. [60]
There is little information on how changes in soil structure, stability, and subsidence could affect pipelines outside of earthquake risks and wave action. [60]  
Pipelines, underground Increases in precipitation (both long-term or droughts/inundation from severe storms) could impact soil structure.
Intense precipitation can erode soil cover and cause subsidence. [60]
There is little information on how changes in soil structure, stability, and subsidence could affect pipelines outside of earthquake risks and wave action. [60]  
Pipelines, offshore      
Aboveground infrastructure (e.g., compressor stations, metering stations, other buildings, structures)      
Utilities for pipelines - electricity - Power losses to pumping facilities and compressor stations can strongly affect operation of pipelines. Pipeline closures during Hurricane Katrina and Rita were due mainly to loss of power rather than physical damage to pipelines.
- Power loss caused disruptions in Hurricane Katrina and Rita; pipeline operators procured electric power generators to resume operations. [33, 60]
   
Electric Power Systems Electric Power Systems - Precipitation can influence types of plants in an area; certain trees (e.g., pines) may be more likely to blow over and damage power lines.
- Soil moisture can impact the stability of poles and trees, making them more susceptible to failure in storms.
- Wet soils--particularly soils with high clay content--may impede the response times of emergency repair crews. [35, 45]
Han et al. (2009b) and Nateghi (2010) investigated the correlation between soil moisture, precipitation and affects on power outages, but did not establish thresholds over which impacts were more likely to occur. [35, 45]  
Marine Ports, Terminals, and Waterways Electrical Equipment Damages from flooding can completely destroy electrical equipment, preventing normal port operations.    
Terminal Buildings Weakening of structures and/or presence of mold.    
Channels - Erosion of supporting sediments; changes in underwater surface and silt build-up.
- In the Great Lakes, lower water levels have increased the costs associated with shipping principal commodities due to the need to increase the number of trips for the same amount of materials. Commercial navigation along the Mississippi River has been similarly affected in recent droughts. The impacts of droughts on the Mississippi is particularly of concern between St. Louis, MO and the Gulf of Mexico. [42, 54, 10]
   
Piers, wharves, and berths Debris and extra sediment can block channels, potentially leading to need for more dredging. [42, 54, 10]    
Port services (i.e., operations) Electrical damages to equipment necessary for operations can shut down or partially restrict operations for a period of time.
Additionally, increases in weather-related delays are likely with more precipitation.
Channels can be blocked from additional debris and/or sediment from flooding. [42, 54, 10]
   

*Note dollar amounts are not adjusted for inflation.

Updated: 03/27/2014
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