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It’s humid out there.

As you know, there’s been a heck of a lot of snow this winter, including more this week. And with all that wetness — the highest amount of frozen water we’ve seen in our mountains in recorded history — comes a natural risk of flooding.

But flooding is not a sure thing. Whether all the water is leaving the mountains quickly or slowly is the main thing and depends on a whole bunch of factors: how fast the snow melts, how high the soil moisture is when it melts, how full different reservoirs are, and so on.

That’s why I wanted to give you the tools you need to stay abreast of the situation from a hyperlocal point of view. How much snow flowing down towards you still needs to be melted? Is the creek near you high enough to be at risk of flooding? Is it likely? How crazy would it have to get for your home to be at risk? Thanks to various local, state, and federal agencies, we have a wealth of scientific data and forecasts that can help you sort this out. Let’s dive in.

Step 1: Understand the country

Of course, which data points are of interest to you depends on where you live. Luckily we have tickets for that.

First, I would recommend looking at the Federal Emergency Management Agency (FEMA) flood map. Here you can see how FEMA considers each location vulnerable to flooding. Some sites are not very vulnerable at all, others are vulnerable to major floods (the 1% or 1 in 100 year flood), others are only vulnerable to exceptionally infrequent floods (0.2% or 1 in 500 years ) endangers flood).

Of course, 1 in 100 is a probability, not an exact science. Unfortunately, just because something was flooded in 1983 doesn’t mean it’s ineligible for flooding in 2023—probably the opposite.

You can see that most of the flood zones are either along one of the valley’s feeding streams or in the lower-lying areas of the valley, generally right in the middle of this map.

Second, here is the Jordan River Basin watershed map. Here you can see all the different streams that eventually flow into the valley.

If the flood zone you’re concerned about is along one of these creeks, you can likely narrow your region of interest to the watershed above. If instead your floods tend to be in the lower-lying areas, you should look at the bigger picture.

Review of the basics

Just believing the predictions below is enough for many, and you have my permission to skip this section if you wish. However, if you want to see the basics of flooding, you can do so through a number of different dashboards.

First snow cover. Salt Lake County has announced that it will release a YouTube video about current and forecast snow cover heights “approximately” every two weeks; Her last video was released on April 4th.

If you don’t want to wait, you can check the snow cover yourself. The National Water and Climate Center of the US Department of Agriculture’s National Resources Conservation Service (wow, what a mouthful) put together a map of snow cover reporting stations here.

You can click on each to see how the snowpack is changing. Here’s a stop at Parley’s Summit.

Of course, as more snow is melted, less water is left on the mountains to cause future flooding. At this point in time, most of the water in our mountains is still in the form of snow.

The USDA map above also allows you to select soil moisture monitoring stations to check how moist soils are in different locations. Drier soils have more opportunity to absorb some of the moisture from melting snow and incoming rain.

Finally, reservoirs can be used to store some of the meltwater; Water engineers can sometimes direct the flow of electricity to or from these reservoirs to control the rivers downstream. The USDA produces a monthly report of current reservoir water storage versus capacity here; The National Weather Service’s Colorado River Basin Forecast Center provides daily (and even hourly) reservoir height measurements at cbrfc.noaa.gov under the Reservoir Conditions tab.

Observing the current flow

However, if you want direct information on how much water is flowing now and how much will flow in the future, there are numerous sources for this more immediate information.

Salt Lake County has an impressive list of water flow sensors installed in its streams to measure how fast they’re moving in real-time in cubic feet of water per second. You can find them at the Realtime Streamflows link on rain-flow.slco.org.

It’s a quick look at where streams are at this second. Yellow stations are currently in “normal high water” conditions, meaning they are carrying a lot of water but are still operating normally. Red stations operate under “estimated flood conditions,” which could result in nearby flooding.

If you click on each station, you can also see a graph of the past few days’ data so you can see how things are going. You can also see the estimated water depth of each stream.

Short-term forecasts of flows

What will happen in the future? The Colorado River Basin Forecast Center – at cbrfc.noaa.gov – has short-term 10-day forecasts of the flow of each of the major watersheds. These monitors are a bit sparser than Salt Lake County’s.

These CRBFC forecasts for each location take into account future precipitation and soil moisture. That’s pretty neat!

Take this example: Here is the graph for the water flows for the station at Emigration Creek, just above Hogle Zoo.

Yes, it flooded down Emigration Creek on April 12th, mostly in the area around Wasatch Hollow Park. But for the next week, we should be fine with no flooding in this area, save for one surprise.

The cool thing is that you can do this with any of the creeks that flow into the valley.

Long-term flow forecasts

The CRBFC also provides longer term forecasts at each river monitoring station – along with an estimated date when those flows could peak. Since we are less certain of what the future weather will be like in more than a week, these forecasts have relatively large certainties. You won’t be able to put them on a chart like the 10-day forecasts above, but put them in a more probabilistic format:

For example, here is the CRBFC’s forecast for its Big Cottonwood Creek station:

The CRBFC says that Big Cottonwood Creek’s flood level is 798 cubic feet per second, and it looks like we have a better than 50% chance of getting at least that mean daily flow. But the peak is unlikely to come until late May or June, according to his latest forecast. That being said, that can change by up to a month either way, depending on the weather.

When to expect peak flow really depends on the stream. The forecast suggests that Emigration Creek flows have probably (but not definitely) already peaked, but the creeks with snow from higher elevations are taking longer to see their peak flows.

Regardless, these are really high flow numbers. Remember that really long-named government agency from the second section? The USDA NRCS NWCC mentioned above produces monthly water supply forecasts for three-month periods – on April 1st they released the forecast for the April-July period. And they predict huge amounts of water flowing through Salt Lake County’s creeks.

In four of these seven forecasts, the most likely outcome is that the water supply records set in 1983 or 1984 will actually be met or exceeded. For the others, reaching heights of 1983 is considered at least possible. That’s pretty remarkable, but let’s not forget to check back on May 1st to see what the new predictions look like.

Hopefully this list of tools can keep you up to date on what’s going on. Even more hopefully, nature will end up working to safely carry the water from high to low elevations and where you are, there will be no flooding.

Andy Larsen is a data columnist for The Salt Lake Tribune. You can reach him at alarsen@sltrib.com.