Modernization of the Harris County Flood Control District Flood Warning System Telemetry Network National Flood Warning Workshop Houston, Texas February, 2012 Don Van Wie, Telos Services R. 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

All sites on a single (overloaded) input channel Two repeater output channels required Original Radio Architecture

Updated System Architecture 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 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 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