Photo By Christine Reinhardt | Lucas Gannon, hydraulic engineer with the Kansas City District, U.S. Army Corps of...... read more read more
If a tree falls in a forest and no one is there to see it, does it make a sound? Similarly, if a heavy rain event causes flooding overnight and no one is awake to see it, did it happen? Of course it did. But, how do you know how high the water got if no one was there to witness it?
This was the scenario facing the City of Merriam, Kansas, after a significant rainfall event occurred overnight and into the early morning of July 17, 2025. Turkey Creek, which runs through the city, is prone to flash flooding during heavy rain events. On July 17, the creek flooded, impacting parts of the city, but it all occurred overnight when most people were asleep. The flood waters receded almost as quickly as they rose, posing the question: how high did the water get?
Thankfully, there are ways to determine how high the water rose and how far it spread after it recedes following a flood event. Conner Szarwinski, hydraulic engineer with the Kansas City District, U.S. Army Corps of Engineers, woke up that morning and knew he wanted to find an answer to that question.
“If you’re not able to physically see how high the water got, we usually go out to try and collect high-water marks,” said Szarwinski. “I opened my phone early that morning and checked some of the stream gage readings along Turkey Creek and I saw this event had actually broken the gage record, which was set back in 2017. That spurred me, once I got to work, to go out and try to collect that information.”
For Szarwinski, proactively gathering high-water mark data served a couple purposes. Not only is this valuable data to have, but it was also a learning opportunity for less experienced engineers at the district. Lucas Gannon, hydraulic engineer, joined Szarwinski in the field.
“I had one of our newer engineers come out with me to assist and then I went out the following week with a couple of our engineering technicians to survey the elevations,” he said. “It was a bit of an impromptu training for our newer engineer and the newer engineering technician, which was beneficial.”
Collecting high-water marks is more of an art than a science. Relying on visual clues, experience and even some intuition, Szarwinski explained how collecting high-water marks can sometimes feel like investigative work.
“The whole process is a group effort. We look for signs or evidence of just how high the water got. Typically, it’ll leave behind a line of sticks or debris, or you might see a line of dirt or sediment on a sign or a building,” he said. “I feel a little bit like a detective looking for evidence in a crime scene.”
Gathering this evidence doesn’t require anything fancy – just a notebook and a camera, according to Szarwinski. Although he will sometimes use a high-water tool kit, which consists of a box of nails, a metal washer and bright orange tape, Szarwinski typically relies on his own notes when collecting high-water marks.
“I’d say the most important method is using my field book – writing as detailed of notes as possible. What it is, where exactly it is and then taking as good of pictures as you can,” he said. “We try to frame the pictures so there’s some identifying reference point so that we’re able to kind of triangulate the high-water mark at a later date to survey.”
Collecting high-water marks is helpful for two reasons. First, measuring these marks helps validate stream gage readings are accurate. Second, having a library of historic data helps inform hydraulic engineers like Szarwinski when designing flood risk reduction projects or conducting floodplain studies.
“It’s useful for calibrating our hydraulic models, which we’re using for the design of the levee system,” he said. “Even if [the data is] not useful to us right now, five years down the line, we might have another project or need to look at the modeling again. So, having that data for future reference is always helpful.”
Although building a library of data is helpful for engineers at USACE, it’s also helpful for the city and county to have access to the data. As for the data Szarwinski and his team collected on July 17, they were able to share it with the City of Merriam for their records.
“We shared the data with the city, and they were appreciative of that,” he said. “We provided them all the surveys at the high-water marks because they weren’t sure how far out of bank [the water] got in some areas. So, it was helpful to kind of reassure them a bit.”
While collecting high-water marks is not an exact science, having this data supports the design of realistic systems, which in turn enhances flood risk reduction efforts – something communities like the City of Merriam depend on.
| Date Taken: | 09.11.2025 |
| Date Posted: | 09.11.2025 11:21 |
| Story ID: | 547833 |
| Location: | US |
| Web Views: | 27 |
| Downloads: | 0 |
This work, ‘Like a detective looking for evidence in a crime scene’: How collecting high-water marks helps flood risk reduction efforts, by Christine Reinhardt, identified by DVIDS, must comply with the restrictions shown on https://www.dvidshub.net/about/copyright.
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