Inland Flooding

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Inland Flooding

• Hector Guerrero,
• National Weather Service San Angelo, TX
• and
• Roy Sedwick, Lower Colorado River Authority and
  Texas Flood Plain Management Association
• National Hurricane Conference
• Austin, Texas, April 9, 2009

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1960 to 2006 5,231 people have lost their life
in flash floods Texas is No. 1 with 737 deaths
177 People Drowned From 1996-2008
Stakeholders from Flash Flood Alley declared
war against flash flood fatalities in the fall of
2007 in response to the 63 Texans who drowned
that year.
Source Hector Guerrero and Jason Johnson/NOAA
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Objectives

• What it is
• Meteorology of Inland Flooding
• Tools to Monitor and Communicate the Lethal
  Threat of Inland Flooding
• Inland Flooding Scenario

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What Is Inland Flooding?

• A potential killer
• Occurs when land falling tropical cyclones
  produce excessive rainfall over inland areas

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NWS Definitions

• Flash Flooding- Short term flood event occurs
  less than 6 hours which require immediate action
  to protect life and property
• River Flooding Issued when a river forecast
  point is expected to rise above flood state and
  usually occurs beyond 6 hours after heavy
  rainfall has ended

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People and Floods Dont Mix
80 percent of the U.S. population live within
200 miles of the coast. The highly-populated No
rtheast U.S. is extremely vulnerable to inland
flooding.
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Flood Related Deaths 1996-2005
Flood Related Deaths Fronts 45 Tropical
Cyclones 22 2 for 1 Deal!
Ashley and Ashley Northern Illinois University
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Highest known tropical cyclones amounts for the
lower 48 since 1971
1) 48.00 inches Amelia 1978 2) 45.00 inches
Claudette 1979 3) 40.68 inches Allison 2001
4) 38.46 inches Georges 1998 5)
36.71 inches Danny 1997 6) 27.85 inches
Alberto 1994 7) 25.67 inches Allison 1989 8)
25.56 inches Dennis 1981 9) 25.00 inches T.D.
1 1992 10) 24.06 inches Floyd 1999
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with Katrina, the deaths due to surge increased
dramaticallybut it is stillimportant to note
that most deaths are caused by drowning!
Dr. Ed Rappaport, 2000
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78 OF CHILDREN KILLED BY TROPICAL
CYCLONES DROWNED IN FRESHWATER FLOODS
Agnes (1972)
Cornell Media Technology Services
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Help Me Tell Every K-12 ChildFlooding Number 1
Weather Related Killer in the U.S.
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Key Points

• What can we do to ensure our fellow Americans are
  educated and aware of this killer?
• Which areas in your community are most at risk
  from inland flooding?
• Will those who are at risk make the right
  decision when they are threatened?

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Using Digital Signs

• TXDoT Dynamic Messaging Signs will display Turn
  Around Dont Drown during times of significant,
  life threatening flooding across Texas

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Floods are dangerous!
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Inland Flooding Factors

• Diurnal Trend of Heavy Rainfall and Size
• Large Scale Weather Pattern and Wind Shear
• Rainfall Rates vs. Amounts (Very Challenging)
• Antecedent Soil Conditions
• Frontal Boundary Interaction
• Size and Topography

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Sometimes The Heaviest Rainfall Occurs at Night
Near The Center and is Called Core Rains
16.83 inches at Del Rio About 11.49 inches fell
in 3hrs --rate of 3.83/hr
9 People killed at Del Rio, State of Texas a
total of 13 See Story
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During the Daytime Tropical Cyclones Expand
Outward
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What Causes Inland Flooding?

Large-Scale Weather Systems Control Cyclone Speed
FAST Steering Flow
SLOW Steering Flow
? How does storm speed and travel affect rainfall
accumulations? ?
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Tropical Storm Allison Path in Texas
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Greens Bayou, Home Owned Estates, 6/10/01 pm
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Highest Rainfall Rates and Total
1 Hour 6.3 3 Hour 13.5 or 4in./hr 6
Hour 21.5 or 3in./hr 12 Hour 28.5 or
2in./hr 6 Day 38.6 Whats more critical
rainfall rates or amounts?
Tropical Storm Allison
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Other Causes of Inland Flooding?

• More than one storm moves over the same area
  (Floyd )
• Wet grounds exist prior to landfall (Agnes)
• Interaction with hills or mountains and/or the
  frontal boundaries

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HURRICANE FLOYD (1999)
Precipitation shield extended well ahead of the
track of Floyd from the Carolinas up the coast
to southern New England Dennis had just
impacted the same area
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Lift Along a Cold Front
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Orographic Forcing
Hurricane Ivan September 13-26 2004
Upslope
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Training Rain Bands
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Key Points

• Worst case scenario is when multiple factors
  combine all at once to enhance rainfall
• T.S. Amelia Slow moving front, Hill Country,
  Core Rains, Weakening (sfc low gone)
• What rainfall rates would adversely impact your
  community?
• What impacts would 5, 10, 20, 30, or 40 inches
  have on your community?
• How will you warn your residents?

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The Team Working With You
Hydrometeorological Prediction Center
National Hurricane Center
Weather Forecast Offices
River Forecast Centers
Regional Offices
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Storm Path
Hurrevac Software
NHC Web Graphic
http//www.hurrevac.com
http//www.nhc.noaa.gov
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http//water.weather.gov
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www.weather.gov
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Tropical Depression Erin Precipitation Estimate
Saturday Night
H
Friday Night
Thursday Night
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Tropical Storm Erin Lesson Learned

• Expected night time heavy rainfall
• NWS communicated estimates of 5 to 10 inches with
  local emergency managers and the media
• San Angelo Emergency Manager placed emergency
  vehicles near major low water crossings and
  possibly prevented many potential drownings

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Monitoring Current Rainfall
Dense Rainfall Network Harris County Flood
Control
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CoCoRahs.org
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MOTION

• Rainfall accumulation is inversely proportional
  to tropical cyclone speed.
• Krafts rule of thumb (1950s)

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Inland Flooding Can Impact Small Streams
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Another Bad Situation
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He Didnt Make It!
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Key Points

• Know the factors
• Build partnerships If you shake hands before the
  disaster, you wont be pointing fingers
  afterwards
• Monitor
• Warn
• Education and Awareness

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Scenario

• Location Is Austin, TX, near the Hill Country
• Slow moving Tropical Storm will reach Austin by
  Friday morning with school in progress and NWS is
  forecasting 10 to 15 inches
• Very little vertical wind shear
• Stationary front in the area

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H
Weak Steering flow
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Latest Hurricane Track

• Hurricane Vince is 200 miles east southeast of
  Austin and is moving northwest at 5 mph and will
  reach the I35 corridor between Austin and San
  Antonio in 2 days.
• Heavy rain and strong winds are occurring over
  the Coastal Bend

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HPC QPF Forecasts
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Scenario

• How much rain and where?
• What are the main factors?
• What are the main impacts?
• Who are your partners?
• How will you communicate with your partners and
  warn the public?
• What will you communicate at this point?

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Radar Just Crashed
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Whats next?

• The rains are moving into the Austin and San
  Antonio I-35 Corridor
• What information do you need now?

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Monitor Rain Gauges
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8.99
8.33
8.33
3.44
8.45
8.47
8.23
8.50
8.55
4.52
8.80
8.78
2.42
8.87
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Key Points

• Understand how the factors can influence inland
  flooding
• Build partnerships If you shake before the
  disaster, you wont be pointing fingers
  afterwards
• Monitor
• Warn
• Importance of Education and Awareness

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Flash Flood Alley War Council What Can We Do
About Inland Flooding?
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Flash Flood Alley Background

• More people drown in Flash Flood Alley than any
  other place in the United States
• Combine a heavy rain event with numerous low
  water crossings and you have the recipe for flash
  flood disaster

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1960 to 2006 5,231 people have lost their life
in flash floods Texas is No. 1 with 737 deaths
177 People Drowned From 1996-2008
Stakeholders from Flash Flood Alley declared
war against flash flood fatalities in the fall of
2007 in response to the 63 Texans who drowned
that year.
Source Hector Guerrero and Jason Johnson/NOAA
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Flood-Related Drownings by Type of Event, Texas
(2007)
Type of Event of Deaths Percent
Flash Flood 42 67
High Water-Related 18 28
River Flood 3 5
Total 63 100
David Zane, Disaster Epidemiologist Community
Preparedness Section, Texas Department of State
Health Services Austin, Texas
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War Council Stakeholders

• Emergency Management Officials from Austin and
  San Antonio
• Texas Dept. of Transportation
• Lower Colorado River Authority
• Texas Flood Plain Management Assoc.
• National Weather Service Offices in Texas
• Area Broadcasters
• State Health Department
• Texas State University
• Harris County Flood Control

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Purpose of The War Council
Two 20-year olds lost in this vehicleonly one
body found

• Strategically create different avenues to attack
  the flash flood problem
• Reduce and/or eliminate flash flood fatalities

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Typical Hill Country Low Water Crossing
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Even with all this, One life lost here!
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Flash Food War Council Strategic Teams

• Flood Awareness and Education
• Watch, Warning and Communication
• Partnership and Funding
• Commuter Preparedness
• Research

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Flood Awareness and Education Team Goals

• Adding "Turn Around, Don't Drown" training to
  Driver's Education and Defensive Driving courses
  and exams
• Working closely with school children, to insure
  they understand flood dangers and safety rules

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Flood Awareness and Education Team Recent
Accomplishments

• TADD Poster Contest- City of Austin, NWS, Austin
  American Statesman and the TFMA
• Austin Media does an awesome job in broadcasting
  Turn Around Dont Drown

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Some goats even wanted to help!!
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FEMA Grant to LCRA

• Disaster Ready Colorado River Basin Interactive
  Disaster Preparedness Website
• Publish brochures, coloring books
• Distribute "Granberg" TADD Video
• Develop several TADD "Giveaways"       

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TADD Stickers
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TFMA Grant

• Publish 18-month TADD calendar
• Purchase Distribute NWS Rain Gages
• Purchase Distribute NOAA Radios
• Develop PSA and/or TADD Video
• Supported development of the Wild Texas Weather
  movie at the Bob Bulloch museum---will have a
  segment on floods and a TADD message at the end
  of the movie

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Watch and Warning Team Goal and Accomplishments

• Reviewing warning text to make it more direct,
  clear and immediate
• Accomplishment- TXDoT Dynamic Messaging Signs
  will display Turn Around Dont Drown during times
  of significant, life threatening flooding across
  Texas

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Partnership and Funding Team Goals and
Accomplishment

• Looking for partnerships in addition to the War
  Council members to leverage resources to help
  promote flood safety
• Developed partnership with The Texas School
  Safety Center (TxSSC) and the new Flash Flood
  Hazard Center (See Research) this past summer

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Commuter Preparedness Team Goals

• Taking inventory of low water crossings in
  flood-prone areas perhaps using GIS
• Encouraging residents who take flood-prone roads
  to develop alternative routes that can be used in
  flooding situations
• Encouraging personal preparedness planning
• Making easily understood flood inundation maps
  available to the public. 
•   
• Looking into the feasibility of suggesting to
  public officials and public businesses to close
  during high confident and extreme flooding
  threats

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Research Team

• Texas State University is developing a Flash
  Flood Hazard Center to tie together the research
  and mitigation practice related to flash floods.
  
• A new laboratory is being established under the
  sponsorship of the James and Marilyn Lovell
  Center for Environmental Geography and Hazards
  Research (JMLC) in the Department of Geography at
  Texas State University-San Marcos.
• The goals and activities of the International
  Flash Flood Laboratory (IFFL) are being developed
  by JMLCs Director, Pam Showalter, and Eve
  Gruntfest who will co-direct the Laboratory.

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Floods are dangerous!
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Acknowledgements

• John Cole, WCM, NWS Newport/Morehead, NC
• Jason Johnson, Hydrologist, NWS San Angelo, TX
• Mary Kay Gordon, Administrative Assistant
• NWS San Angelo Staff
• Amy McCullough, SOO, NWS San Angelo, TX
• Ron Perry and Teresa Covey, San Angelo and Tom
  Green County Emergency Management
• Robbie Berg and Dr. Rappaport, National Hurricane
  Center
• John Metz, NWS Corpus Christi
• Victor Horn, Eastern Region

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