The 2015 Texas Memorial Day Floods are now being labeled a “millennial flood”; they surpassed the standard of what would be considered the severest flood that could occur in a 500-year span.
The Blanco River, and its upstream wet and dry creeks, became engorged with rainwater from a heavy, slow-moving downpour. On the Blanco River in Wimberley, water rose rapidly, reaching what was described by first-hand observers as a “wall of water” estimated to be 40 feet high. This gives the small town of Wimberley the dubious honor of playing host to the highest flood--from normal river flow stages to peak flood levels—in all of the United States.
It is estimated that at peak flood level, water was flowing at 230,000 cubic feet per second, nearly twice the flow of Niagara Falls. More than 350 homes were destroyed, and more than twice that many residences required demolition due to flood damage. Tragically, 12 people lost their lives, including one family whose vacation home was swept away, floating down the river until smashing into the Ranch Road 12 Bridge that leads into Wimberley.
Warnings began on the evening of Saturday, May 23 as reports came from upstream that the Blanco River was beginning to flood. The Hays County Emergency Management office initiated the reverse 911 call system to warn residents along the river of the approaching danger. Wimberley Fire Department swift water teams deployed to begin door-to-door warnings to those individuals staying in vacation homes along the river; there was a potential that many of them did not have landline phones and could not be contacted via reverse 911. The first calls for help came into the station from Dispatch at approximately 9:30 p.m.. By 5:00 a.m. the following morning, the Wimberley Fire Department had received nearly 100 calls for emergency assistance, overwhelming their resources. Mutual Aid assistance was requested from surrounding community swift water response teams, including the City of San Marcos.
An Incident Command was established at Wimberley’s Central Fire Station to coordinate and manage in-bound resources that had been requested. By daylight on Sunday, May 24, the National Guard was contacted to assist in water extractions using two Blackhawk helicopters. Resources from Hays County and other State agencies began filtering into the scene, but were hampered by high water and damage done to the main bridge into Wimberley. All resources had to take alternate routes that were longer and subjected to their own flooding.
Communications became the biggest initial issue as mainlines for telephone, internet, and even power were severed by the debris-filled flood waters. Many officials were relegated to using cell phone text messages to request help and attempt to detail situations in a rapidly evolving scene. Voice communication was limited to very short-range tactical radios. Assistance to re-gain the local communication network was delayed by repair technicians’ inability to reach their destinations.
The event could be categorized in six major phases: 1 – Initial event 2 – Response/Life saving 3 – Damage assessment 4 – Mitigation 5 – Recovery 6 – Preventative planning
The most unusual aspect to this event evolved from a vacationing family that was swept away in a home during the initial flood of Saturday night. Other members of the family mustered an effort to launch a private search for their loved ones. While this sounds benign from an Incident Command standpoint, it had a tremendous effect on operations because of the sheer numbers of people, material, and assets that came to help them.
On flood + day two, they had established a reception center at a local church and had already received 400 volunteers. Included with this was the arrival of up to six Robinson (not related to the author) R-44 helicopters, owned by private parties, intending to operate in the confines of the disaster zone. By flood +day six, this privately funded and managed search effort had more than 1,000 civilian volunteers, dog teams, and other specialists, while the number of private helicopters had risen to 14. This is an unprecedented and unexpected factor for any incident commander to contend with, especially when none of the private parties were familiar with National Incident Management System (NIMS) protocols or Incident Command procedures.
Airspace Activity – First on the Scene
As stated, the first aircraft request by Incident Command was for manned helicopters to assist in the extraction of people trapped on their rooftops by the rising floodwaters. Blackhawks are very capable, all-weather helicopters; two were made immediately available to the Wimberley Valley Incident Command. The weather conditions Sunday morning included rain bands, some wind, and cloud cover ceilings at or below 400’ altitude above ground level (AGL).
Each helicopter methodically searched up and down the river until they spotted flood victims needing to be extracted. While the two helicopters were very well coordinated by their respective pilots in command, there is no question that an unmanned aircraft could have been deployed faster even in this very early stage of the flood event.
The most appropriate unmanned tool for use at this time would consist of several multi-rotor vertical takeoff and land (VTOL) aircraft. The range of this type of unmanned aircraft is rather short, but in a 15- minute deployment, they can scout out ahead of the manned aircraft.
Upon locating flood victims, the coordinates could have been relayed to the manned assets, reducing the time required for the manned asset to visibly “search” for the next victims requiring assistance. It should be noted that there were no other aircraft, civilian or otherwise, in the immediate area because of weather conditions.
This scenario would represent the fewest challenges for airspace de-confliction, as a trained unmanned aerial flight crew would not rely so much upon radio communications as they would their own hearing and visual observers to detect an approaching heavy helicopter. Unmanned aerial flight crew members utilize short-range, handheld radios to maintain communication during a mission. To enhance the safety of operating during this scenario, it is a recommendation that every unmanned aerial flight crew is equipped with a ground-to-air aviation radio and, if possible, tactical communications back to Incident Command and the Air Asset Manager.