Modernization of the Harris County Flood Control District Flood Warning System Telemetry Network National Flood Warning Workshop Houston, Texas February,

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