It is that time of year when the spring snowmelt followed by the start of the Atlantic hurricane season raises concerns about flooding in many parts of the United States.
Despite the attention, with so many flooding events spread across an expansive area, data collection remains a monumental task.
The need for ground truth is critical not only for the people in harm’s way, but also for the professionals responsible for providing services during natural catastrophes, including emergency responders and insurers.
Satellite imagery can solve this dilemma by utilizing analytics designed to detect flooding in an area.
We use the example of recent flooding in Fargo, North Dakota. Late season snow and frigid cold raised the risk of flooding as soon as temperatures rose in the Red River Valley.
In late March, the Red River at Fargo had a 95% chance of reaching 29.5 feet, according to the National Weather Service, just below the 30-foot threshold for major flooding.
As the mercury climbed, the water rose and the river crested at 29.7 feet on April 21-22, but thankfully, the amount of flooding wasn’t as bad as initially feared.
The map below shows Fargo from April 11-27. The flooded area can be seen in dark blue, concentrated along the Red River, which flows south-to-north.
The satellite imagery was collected by our friends at Umbra, using synthetic aperture radar (SAR), a type of sensor that works in any weather conditions, day or night.
We then applied an algorithm designed to detect the presence of water.
Water pixels were extracted and classified separately from existing water bodies to obtain a flood extent map that was used to pinpoint the exact locations where flooding occurred. The results were overlaid on an optical base map.
This specific event proved minor, but the Red River Valley remains one of the most flood prone areas in the country. There are six rivers that contribute to flooding in the Fargo-Moreland area.
After a 1997 flood caused $3.5 billion in damage (over $6.5 billion today when adjusted for inflation), plans were hatched to build a flood control project that would offer reliable and permanent protection for the people living in the area.
What emerged is the Fargo-Moreland Area Diversion Project, a multi-billion dollar undertaking, expected to be complete by 2027, that includes a 30-mile diversion channel, embankment and series of levees.
It’s not the first flood time engineers have tried to control the waters around Fargo.
A smaller diversion project was finished in 1992 to channel the waters of the Sheyenne River, a major tributary of the Red River. To date, the diversion project has not failed, including during record floods of 1997 and 2009.
Read more about Ursa’s flood detection analytics in these areas: