Tropical Storm Allison Tropical Storm Allison & &

its impact on Harris Countyits impact on Harris County

Binbin ChenBinbin Chen

IntroductionIntroduction

• Tropical Storm Allison formed 80 miles off the Tropical Storm Allison formed 80 miles off the coast of Galveston, Texas on June 5, 2001coast of Galveston, Texas on June 5, 2001

• Over the next 5 days, Allison produced record-Over the next 5 days, Allison produced record-setting rainfall, flooding and damage in Harris setting rainfall, flooding and damage in Harris County and city of HoustonCounty and city of Houston

• Because of the magnitude of flooding, Harris Because of the magnitude of flooding, Harris County Flood Control District and FEMA specially County Flood Control District and FEMA specially performed a project “Tropical Storm Allison performed a project “Tropical Storm Allison Recovery Project (TSARP)”Recovery Project (TSARP)”

Flooding after Flooding after AllisonAllison

22 22 fatalitiesfatalities

95,000 damaged 95,000 damaged automobilesautomobiles73,000 damaged 73,000 damaged residencesresidences

Over $5 billion in property Over $5 billion in property damagedamage

Project PurposeProject Purpose

Perform an evaluation of the storm and its Perform an evaluation of the storm and its consequences in Harris Countyconsequences in Harris County

• Storm TrackStorm Track

• PrecipitationPrecipitation

• Stream dischargeStream discharge

• Flooding areaFlooding area

Better understand water resource data and Better understand water resource data and how to integrate different source data using how to integrate different source data using ArcGISArcGIS

Data SourcesData Sources

• National Hurricane Center provides historical tropical tropical ecyclone track GIS data at: ecyclone track GIS data at: http://http://maps.csc.noaa.gov/hurricanes/viewer.htmlmaps.csc.noaa.gov/hurricanes/viewer.html

• National Climate Data Center provides NEXRAD Radar rainfall data at: http://lwf.ncdc.noaa.gov/oa/radar/radarresources.html

• NHD (Unit 1204) & NHDplus (Unit 12a) provide surface water data of Harris County

• USGS stream gages & real time data

• Harris County Flood Control District Provides Harris County watersheds data and flooding area data

• City of Houston provides city land use data

Storm Storm History History &Track&Track

Storm PrecipitationStorm Precipitation

• Rain gagesRain gages

-150 rain gages operated by -150 rain gages operated by Harris County Harris County Office of Emergency Management (HCOEM) Office of Emergency Management (HCOEM)

-3 rain gages operated by National Weather -3 rain gages operated by National Weather Services (NWS) Services (NWS)

• Radar dataRadar data

-NWS collected rainfall radar data at WSR--NWS collected rainfall radar data at WSR-88D radar site covering the Houston area88D radar site covering the Houston area

Downloaded raw radar Downloaded raw radar datadata

Visualize data in Visualize data in NEXRAD ViewerNEXRAD Viewer

Export radar data into Export radar data into ESRI raster data using ESRI raster data using NEXRAD exporterNEXRAD exporter

Obtaining rainfall Obtaining rainfall datadata

Download raw radar Download raw radar datadata

Visualize data in Visualize data in NEXRAD ViewerNEXRAD Viewer

Export radar data into Export radar data into ESRI raster data using ESRI raster data using NEXRAD exporterNEXRAD exporter

Storm Total Storm Total RainfallRainfall*One Rain gage at Greens Bayou *One Rain gage at Greens Bayou recorded the highest rain as 38 recorded the highest rain as 38 inches.inches.

Total Total RainfallRainfallfrom June 5 to June 7from June 5 to June 7

14-hour Rainfall14-hour Rainfall

Source: TSARP Source: TSARP reportreport

Stream Stream dischargedischarge

Source: TSARP reportSource: TSARP report

Flooding Flooding AreaArea

Flooding Flooding land land in Houstonin Houston

Flooded Major Flooded Major RoadsRoads

ConclusionConclusion

• Tropical Storm Allison was the most Tropical Storm Allison was the most damaging tropical storm in Harris County.damaging tropical storm in Harris County.

Harris County received the heaviest rainfall from Tropical Storm AllisonHarris County received the heaviest rainfall from Tropical Storm Allison Streams in Harris County were greatly affected by Tropical Storm Allison, Streams in Harris County were greatly affected by Tropical Storm Allison,

17 out of 44 stations reached record peak flow on June 19,200117 out of 44 stations reached record peak flow on June 19,2001 A large amount of lands & roads in Harris County were flooded.A large amount of lands & roads in Harris County were flooded.

• ArcGIS has the powerful function to ArcGIS has the powerful function to integrate different source data, visualize integrate different source data, visualize and analyze data, and depict a clear and analyze data, and depict a clear picture of the storm event, which helps picture of the storm event, which helps people understand flooding and flood risk people understand flooding and flood risk and better prepare for the next “Allison”.and better prepare for the next “Allison”.

QuestionQuestions?s?