Modernization of the Harris County
Flood Control District
Flood Warning System
Telemetry Network
Don Van Wie, Telos Services
R. Chris Roark, Blue Water Design LLC
Jeff Lindner and Jim Greeson, Harris Co FCD
National Flood Warning Workshop
Houston, Texas
February, 2012
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
50%
8000
45%
7000
40%
6000
35%
5000
30%
25%
4000
20%
3000
15%
2000
10%
1000
5%
0%
1-0:00
0
1-12:00
2-0:00
2-12:00
3-0:00
3-12:00
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
Original Radio Architecture
ALERT
169.425
ALERT
169.425
ALERT
Base
ALERT
Repeater
HCFCD
Gages
171.825
ALERT
169.425
MHz
ALERT
Repeater
170.225
HCFCD
Gages
ALERT
169.425
Partner
Gages
• All sites on a single (overloaded) input channel
• Two repeater output channels required
Partner
Gages
Updated System Architecture
ALERT2
171.825
ALERT
170.225 MHz
Dual
Channel
ALERT2
Concentrator
HCFCD
Gages
ALERT
169.425 MHz
Partner Gages
ALERT2
171.825
ALERT2
Base
ALERT2
171.825
• Two gage input channels
• ALERT Concentration
increases capacity
ALERT2 Features
• Concentration yields tenfold improvement in
ALERT throughput
• Forward error correction
• TDMA – efficient channel utilization
Time Division Multiple Access
ALERT2
Concentrator A
•
•
•
•
ALERT2
Concentrator B
ALERT2
Concentrator C
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
70.0%
60.0%
Data Loss %
50.0%
40.0%
30.0%
20.0%
10.0%
0.0%
0
2000
4000
6000
Hourly Traffic Rate
'Before' - April 2009
'After'- October 2011
8000
10000
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
171.825
ALERT
170.225 MHz
Dual
Channel
ALERT2
RepeaterConcentrator
HCFCD
Gages
ALERT
169.425 MHz
Partner Gages
ALERT2
171.825
ALERT2
Base
ALERT2
171.825
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