It has been just over a week since Hurricane Ian made landfall as a category 4 hurricane in Florida, causing devastation and flooding across southwestern and central Florida. Days later, Ian made a second U.S. landfall in South Carolina as a category 1 hurricane and continued its northward trek dumping heavy rain across several southeast and mid-Atlantic states.

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From Florida to Delaware, U.S. Geological Survey crews are wrapping up fieldwork efforts to retrieve equipment that was installed before Ian made landfall. This includes more than 250 water level sensors deployed along the Gulf and Atlantic coasts that measured storm surge and wave heights. Soon after the sensors are collected, their data will be processed and made available to the public.  

Scientists use data collected by these sensors to improve storm surge forecasts and coastal change models. Engineers use the data to design structures to better withstand storm surge and floods and the information can also help inform land-use practices and building codes that can lead to more resilient coastal communities.

Crews are also recovering more than 40 rapid deployment gauges, which were temporarily installed at critical locations to monitor rivers and streams and augment the USGS nationwide streamgage network. Rapid deployment gauges provide near real-time information to the public and emergency managers tracking floodwaters. The water level sensors and rapid deployment gauge data can be found on the USGS Flood Event Viewer.

Some post-Ian USGS science efforts in Florida will last for weeks

In Florida, in addition to collecting water level sensors and rapid deployment gauges, crews are also repairing USGS streamgages destroyed or damaged by Ian and measuring floodwaters in several parts of the state.

More than 50 streamgages were damaged by the storm and USGS crews have repaired most of them. However, the devastation Ian has caused in southwestern Florida has made it difficult for crews to access many of the still damaged streamgages due to road closures, destroyed infrastructure and flooding. Efforts will continue to reach and repair the streamgages until the work is complete.

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After a storm, repairing damaged streamgages is important because USGS streamgage data on water levels and flows can help inform critical decisions such as evacuation plans by emergency managers; coastal and inland flood forecasts by the National Weather Service; and flood-control decisions by the U.S. Army Corps of Engineers.    

Measuring floodwaters to validate USGS streamgage readings is another priority during flooding. Crews in Florida have been working for days measuring high water in dozens of rivers and streams across the state. This work has enabled USGS experts to determine that almost 50 streamgages in Florida with at least 10 years of historic records have each logged a new water flow record, which means it’s the highest volume of water ever measured at these gauges. While these data are preliminary and subject to change with further study and review, one thing is clear, Ian has caused historic and record-breaking levels of flooding across the state.  

Preparations are currently underway for an extensive effort to collect high-water marks across Florida to determine the extent of the flooding caused by Ian. The focus will be areas hit with widespread coastal and inland flooding and includes places in Gasparilla, Pine, Sanibel, Little Hickory and Estero Islands, Cape Coral, Fort Myers, Bonita Springs, Estero, Fort Meade, Campbell, Kissimmee, Orlando, Astor and Palatka.

High-water marks are telltale signs of flooding and consist of lines of seeds, leaves, grass, dirt and other debris deposited by floodwaters on things like stream banks, tree trunks, buildings, bridges and other structures. The physical evidence of flooding provided by high-water marks is valuable information that USGS experts can use to reconstruct precisely where, to what height, and in what volume floodwaters inundated a region. Right after a storm, the USGS’s early information from high-water marks can help emergency managers make informed flood management decisions. The data can also help emergency managers as they plan for future floods and inform the computer models used by the National Weather Service to forecast flooding.

High-water marks can easily be destroyed by rain or communities cleaning up after a storm so they must be flagged and measured as soon as it’s safe to do so. While some of this work has started, the main effort will begin as early as this weekend when the USGS plans to deploy 10 crews to scour these areas of Florida to find and measure the valuable high-water mark data before they disappear.