USGS monitor ice jams in Nebraska, a possible source of flooding this spring

Rachael McLeod: Welcome to the sixth episode of Nebraskast, where we talk with real USGS scientists about the important water resources work they're doing all over Nebraska. My name is Rachael McLeod, and I'm here with Jason Lambrecht of the Nebraska Water Science Center to talk about a common problem this time of year, ice jams. What is an ice jam and why can it be a problem, Jason?

Jason Lambrecht: An ice jam is a buildup of broken ice in the river systems. It can be a problem in that it causes the water to back up over top of highway bridges, roads, into cities. It can cause flooding.

Rachael McLeod: How serious can that be?

Jason Lambrecht: It depends on the magnitude of the ice jam. If the ice jam is a large one, it can back up the water for miles. If it's small, it can just back it up more locally.

Rachael McLeod: Can it damage infrastructure or bridges?

Jason Lambrecht: The ice jam itself can damage the bridges. With the amount of water pushing on the ice jam from behind, it can force the ice to push the bridge - moving it slightly.

Rachael McLeod: What kind of temperatures do you have to have, how cold does it have to be and how long in order to start seeing ice buildup and the threat of ice jams?

Jason Lambrecht: Well, like ice in your freezer, ice starts to form at 32 degrees Fahrenheit, and the longer the temperatures stay below 32 the more ice will build up inside the river. Now when the rivers begin to pick up more flow in the springtime when the weather gets a little bit warmer or if there's a significant rainfall, the ice starts to break up - flowing downstream and that's when it can start to jam up at constrictions in the river, such as bridges or natural constrictions as well.

Rachael McLeod: Are we starting to see any ice buildup or signs of ice jams in Nebraska?

Jason Lambrecht: So far, we aren't seeing any ice jams yet, but we're doing a lot to monitor those ice jams.

Rachael McLeod: In what sense?

Jason Lambrecht: We currently collect ice thickness information when we go do regular stream-gaging work or when we're measuring discharge on the rivers. We currently have five crews out right now checking ice thicknesses, as they do their regular stream-gaging work.

Rachael McLeod: So right now maybe what we're seeing is the water's freezing, you're getting ice accumulation, then the ice jams might come later as temperatures start to warm then and things start to break up?

Jason Lambrecht: Correct. When the temperatures do start to warm up in the near future, the ice will start to break up at that point. The speed at which it breaks up will be a factor. And the thickness of the ice is also a factor for how bad the aftereffect can be from the ice jams.

Rachael McLeod: Where can someone go to see some of the information that we're collecting about ice and the potential for possibly rising waters as a result of ice jams?

Jason Lambrecht: We don't put the ice information itself on our Web page. We do have water-level values that are collected at about 90 stream-gage locations across Nebraska. And monitoring those water levels can show one if there is backwater coming in from ice or not.

Rachael McLeod: And this is real-time data, too, so in some cases those water levels are being transmitted via satellite every few minutes or so, correct?

Jason Lambrecht: Correct. About every hour, there is 15-minute values coming in from about 90 locations across Nebraska. The Niobrara, the Platte, the Elkhorn and the Loup River Basins, we're monitoring stream-gage information, and when you see these rises in the stream gages, the rises of the water level, that's maybe an indicator that ice jams are forming somewhere downstream in those sites.

Rachael McLeod: So, Jason, I hear that there is another resource that might be available to the public sometime here later this spring that they can use to help notify them maybe if some flooding starts to occur. Tell me a little bit about that resource.

Jason Lambrecht: Well, this resource is called the Hydrologic Notification System, and it should be coming out in about May. This notification system is a tool. The user can define streamflow or a water level of interest to them, and when the actual stream conditions get above or below these levels that they put in, a text or an email will be sent to the user to let them know.

Rachael McLeod: Who else might be interested in this information? Who else could use it? What other agencies might be using it for their own benefit?

Jason Lambrecht: We passed that information along to the National Weather Service and to the core of engineers, and they use this ice thickness data for their flood forecasting and for their modeling. We also would pass this information along to any other entity that wants it.

Rachael McLeod: Well, Jason, I'd like to thank you for taking the time to talk to us. And stay warm out there.

Jason Lambrecht: Thank you very much.

Rachael McLeod: To contact Jason directly, please email him at jmlambre@usgs.gov. Or to find out how you can receive alerts via email or cell phone about water levels at any of the 90-plus real-time USGS stream-gaging stations across Nebraska, please visit us on the Web at ne.water.usgs.gov.

This podcast is a product of the US Geological Survey, Department of the Interior.