Modernization of the Harris County Flood Control District Flood Warning System
Telemetry Network
National Flood Warning WorkshopHouston, TexasFebruary, 2012
Don Van Wie, Telos ServicesR. Chris Roark, Blue Water Design LLC
Jeff Lindner and Jim Greeson, Harris Co FCD
HCFCD Flood Warning System
• 267 Sites
• 887 Sensors
• 10 Agencies
Flood Warning System Agencies
• Harris County Flood Control District• Texas Department of Transportation (TxDOT)• San Jacinto River Authority• Trinity River Authority (Livingston Dam)• Sugar Land• Pearland• Fort Bend County• METRO• City of Houston• Brazoria County
The Telemetry Network
ALERT Traffic and Data Losses, July 2, 2010
• Does the system have the capacity to handle major events?• With 250 rain gages, more than10,000 Reports/Hour is possible
Why do data losses matter?
• ALERT handles missing rain reports well; accumulator values ‘bridge’ across lost reports
• Other reports lose timeliness; probability of missing several reports in a row goes up more rapidly than the data loss rate
• During rapid rise, lost reports can lead to invalidation of good reports that follow
Radio System Changes
• Added second input frequency– HCFCD changed to new frequency– All other agencies remain on original frequency
• Combined all data onto one contention-free output channel using ALERT2 concentrators
• Balanced loading on repeaters
ALERT Base
ALERT Repeater
HCFCD Gages 171.825
ALERT169.425
ALERT 169.425
MHz
Partner Gages
HCFCD Gages
Partner Gages
ALERT Repeater
170.225
ALERT169.425
ALERT169.425
• All sites on a single (overloaded) input channel• Two repeater output channels required
Original Radio Architecture
Updated System Architecture
ALERT2 Base
Dual ChannelALERT2
Concentrator
HCFCD Gages
ALERT2171.825
ALERT170.225 MHz
ALERT 169.425 MHz
Partner Gages
ALERT2171.825
ALERT2171.825
• Two gage input channels• ALERT Concentration
increases capacity
ALERT2 Features
• Concentration yields tenfold improvement in ALERT throughput
• Forward error correction
• TDMA – efficient channel utilization
ALERT2 Concentrator A
ALERT2 Concentrator B
ALERT2 Concentrator C
Time Division Multiple Access
• Each Concentrator (Repeater) has its own time slot• Multiple repeaters use same channel without contention• Clocks are synchronized by GPS• Freed up one frequency for use as a second gage input
channel
Traffic Capacity Has Doubled
The Path Forward
• Repeaters: Add ability to repeat ALERT2 messages as well as concentrate ALERT messages
• Begin deployment of ALERT2 gages with TDMA
• ALERT2 gages will replace ALERT gages as system continues to modernize
• Each agency can progress independently
ALERT2 Transition Path
ALERT2 Base
Dual ChannelALERT2
Repeater-Concentrator
HCFCD Gages
ALERT2171.825
ALERT170.225 MHz
ALERT 169.425 MHz
Partner Gages
ALERT2171.825
ALERT2171.825
ALERT2 Gages
ALERT2 Expected Outcomes
• Capacity to reliably handle severe storm events, hurricanes
• No corrupted data
• Complete and timely information.
Challenges
• Overloaded radio channel
• Difficult to administer
• Aging infrastructure
• Damage from Hurricane Ike
HCFCD Responses
• Upgraded infrastructure - installed new instrument housings
• Modernized base station hardware and software
• Improved operating procedures; maintenance metrics and performance tracking
• Reconfigured network architecture using ALERT2
New Instrument Housings
Software Upgrades
• New data collection software and tools– Browser-based, Graphical User Interface– Data visualization, data export
• Integrated Web access permits staff to work where the storm finds them
• Two fully redundant, freestanding receiving sites and base stations with data synchronization in real time
• Extensive reporting tools and performance metrics