A number of coastal towns and communities suffered significant damage from 130mph winds and associated storm surge caused when Hurricane HARVEY made landfall as a Category four storm on 25 August 2017. Further wind damage inland was not seen as HARVEY quickly dissipated and stalled over the region. This stall allowed HARVEY to cause historic rainfall levels across the region which in turn caused flooding consistent with what Federal Emergency Management Agency (FEMA) termed in 2015 “0.2% Annual chance of flood hazard” predominantly in Houston; a low lying city with a number of major rivers and bayous crossing through it.
As a result of continued rainfall from Hurricane HARVEY, the city of Houston and the greater Houston area (including Galveston) saw up to 1.32m of rainfall over the period of 26 August - 30 August. This rain fell on onto already waterlogged ground, causing local dams, tributaries, rivers and bayous to become deluged and to rapidly burst their banks, leading to large scale flooding events across the city.
The US Corps of Engineers were also forced to release water from the Addicks and Barker reservoirs to ease the strain on both dams as they were are at record highs. This release of the water meant that homes and streets downstream also flooded with some homes being inundated for up to a month.
MIS had tracked Hurricane HARVEY from its genesis as a Tropical Wave to the east of the Lesser Antilles in the Caribbean Sea. Analysts were already formulating which Sources and Agencies (SANDA) they would use if triggered by the LMA.
This SANDA included:
- National Aeronautics and Space Administration (NASA)
- Federal Emergency Management Agency (FEMA)
- National Hurricane Centre (NHC)
- National Weather Service (NWS)
- United States Geological Survey (USGS)
- National Oceanic and Atmospheric Administration (NOAA)
- Social Media (Twitter, Instagram, FaceBook)
- Closed Circuit Television (CCTV) systems throughout the states affected including Webcams and traffic cameras.
- Local, National and International News / Media outlets
Due to HARVEY’s prolonged stall over Texas, satellite imagery could not initially be sourced. Synthetic Aperture Radar (SAR) Imagery was sourced from the SENTINEL-1 platform which gave some broad results for flooding in Houston but the results were too broad and inconclusive probably due to false returns from the built up natures of downtown Houston. Imagery from NOAA airborne sensors was eventually used as the platform was able to fly under the dense cloud cover of HARVEY.
Guided by the initial SAR imagery, analysts were able to compare pre storm imagery against post storm imagery and determine at individual property level where the flooding had occurred and the assessed damage levels to each property. This included properties where the flooding had receded between the storms arrival (26 August 2017) and image date (31 August 2017).
MIS Analysts are all former British Military Intelligence Analysts with a broad range of experience in UK Military Operations. They are also graduates of the UK Military Imagery Analysis Course and have a wealth of knowledge in remote sensing and imagery analysis. In addition, the Analysts are highly experienced in the use of Geospatial Information Systems (GIS) and use QGIS in order to extract and display information gained from the integration of information and imagery.
Houston, Post Hurricane Harvey - © NOAA 2018
MIS were able to provide detailed support to Managing Agents in respect of risk and claims across large parts of Texas following Hurricane HARVEY’s landfall. This was provided 72 hours after the storm's arrival despite the fact that satellite imagery was unavailable for use.
The innovative use of SAR which was later refined by other imagery provided an almost immediate ability for insurance leaders to understand the situation on the ground and helped to determine the damage levels to individual properties within a large scale urban city.
Created By: Oz Smith © 2019