ALERT Low Water Crossing Warning Systems

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ALERT Low Water Crossing Warning Systems

• Produced by
• Rand Allan, Associate Meteorologist
• County of San Diego Flood Control

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The Need for Low Water Crossing Warning Systems

• Flooding claims scores of lives each year
• Each foot of water rise displaces up to 1500 lbs
  of vehicle weight
• Lateral force of a flooding stream can place over
  500 lbs of force on a vehicle
• Small vehicles and pedestrians can be swept off
  the road in as little as 6-12 of water
• Flood waters can hide washed-out crossings

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Low Water Crossing Warning Devices

• Three
• Examples

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Stand-Alone System

• Warning light activates when water over the road
• Good for remote, lightly traveled areas with
  little accident history
• However, there is no notification given to
  authorities

• Relatively inexpensive, cost about 1,000 -2,000
• Can be built in-house
• For about 2,500 more they can be modified for
  ALERT radio transmission

Warning Flasher - Scottsdale, AZ
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Automated ALERT Signals

• Under control of ALERT system
• As water first flows over road, lights flash
  yellow sign says use caution when crossing
• As water reaches 6 over road, lights flash red,
  sign changes to road closed condition
• Sensor can be installed to detect washed-out road

• Station can phone agencies to warn of flood
  events
• Agencies can phone station to get current
  conditions
• Cost is moderate, about 15,000 to 20,000
• Good for moderate traffic areas with low accident
  rate

ALERT Flasher - Harmony Grove, CA
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ALERT Signal/Barrier System

• Station will call agencies to warn of flooding
• Agencies can call station to get current status
  of crossing
• Closed circuit loop in road can detect road
  washout and close barriers
• Installation is useful where heavy traffic causes
  a high rate of incidents
• Installation is expensive - 100,000 to 150,000

• Under control of ALERT System
• Barriers prevent crossing the stream when water
  depth reaches 6 over road
• Sensors in road prevent motorists from becoming
  trapped between barriers
• ALERT transmits water levels and times of road
  closings

ALERT Flasher/Barrier - Spring Valley, CA
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Benefits of Warning Systems

• Real-time water levels for crossing safety
• Immediate notification of start and end of road
  flooding and closure
• Reduced overtime costs waiting for roads to
  flood
• Road crews can attend to other priorities
• Legal protection for govt agencies
• No excuses for not knowing it was hazardous to
  cross

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Considerations

• Requires dedicated maintenance
• Initial cost can be quite expensive
• Design of system has to match the needs of the
  low water crossing
• Procedures need to be established between
  agencies
• Legal regulations may need to be established

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Low Water Crossing Systems
For further information, please contact Rand
Allan [phone] e-mail rallanpw_at_co.san-diego
.ca.us