Skip to content Skip to main navigation Report an accessibility issue

Use of Small Unmanned Aerial Systems for Emergency Management of Flooding

By Matt Cate

Small UAS used by Fort Bend, Texas, Office of Emergency Management before, during, and after Hurricane Harvey flooding Center for Robot-Assisted Search and Rescue)

It seems like Unmanned Aerial Systems (UAS), or drones, are everywhere. We see them in the news as military weapons and intelligence systems. We see that companies like Amazon want to use drones to deliver packages to our homes. As their cost decreases, drones are even available as toys. As this technology becomes available to almost anyone, some experts worry that drones could bring down other aircraft through accidental mid-air collisions or even be used against us by terrorists.

But if you watch closely, you may also notice that drones are increasingly useful to those of us in transportation and public works. Many parts of Tennessee experienced flooding in the winter of 2019. Newscasts and social media sites were filled with aerial videos of the flooding and the resulting damage to homes, businesses, and roads. These same videos can be used to provide valuable information to the public officials who must manage these events before, during, and after the floods.

The following excerpts from FHWA’s Use of Small Unmanned Aerial Systems for Emergency Management of Flooding Tech Brief (FHWAHIF-19-019) discuss seven basic UAS applications available to emergency management and transportation officials during flood events.

 

Why Focus on Floods?

Flooding is a unique event or occurrence: it may be a standalone incident, or it may accompany another event. As examples, a hurricane may produce flooding as well as wind damage, or a landslide may dam a river and create a flood. Flooding events are unique in terms of their scale of occurrence or time.

There is likely some warning prior to a flooding event, and flooding is generally a long duration event, when it can be weeks or months before flood dangers subside. The event may be a series of floods, with a flood from initial intense rain directly falling in the affected area, followed by river flooding from drainage or upstream rain moving into the area, as seen with Hurricane Harvey in the metropolitan Houston, Texas, area.

Flooding impacts can be gradual or sudden, such as the levee breach in New Orleans, Louisiana, with Hurricane Katrina in 2005. Flooding poses immediate threats to personal safety and infrastructure, along with general risks of hazardous material leaks or spills. Flooding may as also result in search and recovery of missing persons.

The Seven Basic Small UAS Missions

UAS missions can be divided into seven basic categories, as described below. UAS have been used for all seven categories for flooding events, although not all seven for a single event. Missions provide either images and video, digital elevation maps, or photogrammetric stitching of images into an orthomosaic image. Some of these missions are directly related to your responsibility for roadways and other transportation infrastructure, while others would represent an opportunity to assist other agencies in floodrelated operations (these are marked with an asterisk).

Strategic Situation Awareness, Survey, and Reconnaissance

Strategic situation awareness (SA), survey, and reconnaissance consists of multi-purpose scans of the area. Depending on the specifics of the mission, the flights may be either real-time video and imagery or photogrammetric mapping. Typically, situation awareness favors a cinematic style of flying to give the viewer the sense of the area, while surveys and reconnaissance favor specific paths (e.g., lawnmower scans, follow a river).

For floods, the objectives of this category of mission are to answer questions such as where’s the flooding? How bad? Are people in distress? What is the state of the transportation infrastructure, roads and bridges?

Another application is to identify easement and standing water conditions that prevent power utility crews from restoring electricity. Hazardous material leaks are a real concern; What’s that sheen on the water? diesel? chemical? sewage? and where is it coming from? Are those propane tanks floating away?

Another use is to identify stranded livestock. Strategic SA can be used to inform the public about the flood, the impact on individuals or their relatives, or why evacuation orders are in place, especially if data are readily available on a social media site.

Detailed or Structural Inspection

The detailed or structural inspection mission is about experts examining built structures via either a quick look or a formal examination. One example is the examination of levees for signs of overflow (over the top) or for seepage (indicating incipient collapse). The most informative imagery is dependent on the structure and damage, and thus it is helpful to have an expert with the UAS team to direct the flight.

The flight may require more elevation (oblique) views than plane (nadir) views. Three-dimensional (3D) reconstruction is generally not used for the quick assessment.

This type of inspection is generally performed 10 feet (3 meters) away from the structure, which can be very challenging due to poor global positioning system (GPS) signals and wind shear. While some platforms have obstacle avoidance mechanisms, these mechanisms may be unreliable in such challenging conditions.

Debris, Flood Estimation, and Damage Assessment

Debris, flood estimation, and damage assessment is more detailed than general reconnaissance and more focused on documenting boundaries of an event, counting affected houses, and relating the current state of the area to the prior conditions. This type of assessment can enable drainage experts to confirm flood inundation maps and determine causes of variances (e.g., a fallen tree acting as a dam).

The mission might enable rapid volumetric estimations of debris after the flood recedes. It can also document land use and drainage issues to be resolved later.

This mission can be accomplished with real-time video and imagery (e.g., the drainage confirms that the flood boundary matches expectations) or with photogrammetric mapping for formal analysis of the extent of the flood.

Tactical Situation Awareness

Tactical SA uses a UAS to help the rescue team assess the condition of roads or bridges ahead to decide where to go from their current location. It also permits overwatch of teams or canines, or in swift water rescue oversight of floating debris that might jeopardize crews in boats, thereby increasing responder safety. Use of UAS for tactical SA is a common practice with the Florida State Emergency Response Team (SERT). UAS also has a place in traffic monitoring and detour routing efforts, providing needed viewpoints for transportation planning.

Ground Search and Rescue*

In this mission, the UAS is generally assisting with the search for a missing person, object, or scene that is on the ground. In a flooding event, victims may have been swept away by the flood and the ground search is conducted after the waters have receded. For this mission type, high- resolution images are the most valuable, as video may be too difficult to freeze frame or lose resolution when paused.

Water Search and Rescue*

Water search and rescue is typically associated with a marine incident, although for a flood this includes a swift water rescue. A water search may be combined with a ground search for a victim after a boating accident on a lake where they possibly swam to shore, or a flood where a survivor may have been swept away but climbed out.

Delivery*

This mission is for the UAS to facilitate delivery of material to any location. However, extreme care is needed when flying near people because operators tend to lose depth perception and may get far too close to objects and people. In addition, some platforms or payloads may not be able to maneuver safely for this mission type; something hanging off a small UAS changes the dynamics of the vehicle, creating a pendulum effect, so it may behave and move unpredictably.

Learn More about UAS Applications in Transportation


Back-Contents-Forward