This page will be updated with the most recent information about seasonal runoff, snow and water levels, and potential flooding. Check back often, as it will be the most current source.
May 22, 2023: Our City engineers have stopped reporting snowpack water levels to us because the data is no longer reliable. The Public Works Director went on a short flight over the drainage area last week and observed mostly bare ground even in high elevations. We have observed declining flows over the last week, and as of this afternoon, Mantua Reservoir was about 8.5 inches below spill level. The level has been raising about 1.5 inches a day, even with the hydropower generators going at full capacity. City staff have decided to allow it to fill to about 4 inches below spill and maintain it at that level to allow some leeway in case of heavy rains.
We expect flows to continue declining gradually, even though we will experience higher peaks as temperatures raise and if there is rain.
May 15, 2023: The Little Bear station that we have previously relied on for snowpack water data has now completely melted, so we are relying on two stations on Ben Lomond. This means our data is less reliable now because those stations are not in our drainage area. That being said, our best estimate is that we still have about 714 acre-feet of snowpack water in the Mantua Drainage Basin and another 6,272 acre-feet in the Box Elder Creek Drainage Basin. That's a total of 6,986 acre-feet.
Our Public Works director is scheduling a flight for later this week to get some eyes on the high elevations and make a visual comparison between his last flight almost two weeks ago and now. We believe we are at peak runoff now. Barring a heavy rain event, we expect a gradual decrease in average creek flows—with some periodic spikes—over the next month or two, with high elevation snow expected to last into July.
May 8, 2023: About 60 percent of the snowpack water has now come down, and flows over the last couple of days have slowed a little. The Mantua Drainage Basin is still holding on to about 1,046 acre-feet of water, and the Box Elder Creek Drainage Basin still has about 8,675 acre-feet left. We are running 2-3 weeks behind a typical runoff year due to snow accumulating well into April. According to the current 10-day forecast, temperatures will stay mild with very little chance of rain. We believe the heaviest runoff will be over within the next two weeks.
May 1, 2023: A little over 50 percent of the snowpack water has come off the mountain from the high point a few weeks ago. We currently have about 1,922 acre-feet in the Mantua Drainage Basin and 9,822 acre-feet in the Box Elder Creek Drainage Basin (11,744 total acre-feet). The daytime temperatures are warming significantly and the overnight temperatures are no longer dropping to freezing. We will continue to see runoff increase over the next few days.
In today's flood control meeting, City staff who have been around a long time discussed their experiences with previous flood events. They agreed that all the events they could remember were triggered by a weather event, not just normal runoff. Our Public Works department has done a great deal of mitigation work over the last several years (since the 2018 flood event) and believe the infrastructure can handle the runoff unless is it compounded by additional factors such as heavy rain or prolonged warm winds.
That being said, our snowpack water level this year is unprecedented, and warm temperatures are likely here to stay. We are hoping for the best while preparing for the worst.
April 24, 2023: We are now at 18,342 acre-feet of water in our drainage basins, with 2,877 in the Mantua Basin and 15,465 in the Box Elder Creek Basin. This is a 25 percent reduction over the high we experienced a couple weeks ago, but it's still more water than we've had in at least the last 10 years.
May 22, 2023: Nothing new to report, other than City staff are making arrangements for the storage of sandbags. This will be the last update unless the situation changes and we experience flooding.
May 15, 2023: City staff are focusing on filling Mantua reservoir while also maintaining maximum power generation. We will continue to carefully monitor water levels over the next few days as we potentially hit 80 degrees.
May 8, 2023: The Public Works staff is spending most of their time on some aspect of flood prevention or mitigation when they aren't providing scheduled services like garbage pickup. Over the last several days, they have made small periodic adjustments to various components of the water collection system—sometimes as often as every 10 minutes for a time—to carefully control flows down the creek. We have video feeds on several key points and those are monitored nearly constantly.
Crews have been working to remove silt from drainage areas while flows have been lower over the last couple days. By removing that silt, more space is made for water when flows increase again. These efforts have to take place when flows are lower for safety reasons. Crews constantly have to weigh safety risks in all of their mitigation efforts. Sometimes, they may determine that a logjam or other debris cannot be immediately removed because it is too dangerous.
Several residents have asked why the City doesn't send water through the irrigation system to lower the level of Box Elder Creek. There are a number of reasons for this, including: (1) the irrigation system is not owned or run by Brigham City, but by a user association; (2) the irrigation system currently has a lot of debris in it; and (3) the irrigation system is comingled in some places with the City's storm water system. Running water through the irrigation system would cause water to back up across roadways and on both public and private property.
May 1, 2023: We will start to see some significant runoff over the next couple of days, but then the temperatures are forecasted to drop again and we believe the runoff will slow down. Crews are carefully monitoring the creek and reservoir and are in constant communication with each other.
We spent a few days last week running the hydropower generators half the time, but quickly returned to 24/7 production because of the amount of runoff flowing into Mantua Reservoir. The reservoir level has risen over a foot since last week, even with the Power Department running the hydropower generators.
April 24, 2023: The time has come to do some careful juggling as City staff aims to prevent flooding while still filling Mantua Reservoir. The forecast is still favorable, although it will be warming significantly and not getting quite as cool overnight. In today's flood control meeting, City staff decided to reduce the amount of water we draw from Mantua Reservoir by about half. Residents along the creek may notice lower flows during the day and higher flows in the evening. This is because, rather than run the hydropower generators at half capacity 24/7, Brigham City Public Power will run them at full capacity during peak demand. The schedule allows us to reduce the amount of water drawn from the reservoir by half while maximizing the benefits of power generation to our residents.
City crews have identified some potential blockages that were previously hidden by snowpack, and have either cleared them or have plans to clear them as soon as it is safe to do so. Residents might notice track-hoes or other pieces of large equipment placed near culverts or bridges to provide quick access if needed.
We are also coordinating with other local water companies to ensure they don't send water into our system as a way to manage their own overflow during the runoff period.
Not necessarily, although we encourage residents to prepare for it because we can't say for certain one way or the other.
Last time Brigham City experienced significant flooding was in 2018. At that time, there was very little snowpack in the mountains, but the ground was covered in frost. A quick warmup plus frozen ground meant the snowmelt couldn't be absorbed into the ground, resulting in runoff that overflowed Box Elder Creek. A year later, in 2019, we had nearly 5 times as much snowpack in the mountains. But because the conditions were better, Brigham City experienced no runoff at all. Everything was absorbed into the ground as the weather warmed more slowly.
This year, conditions are more like 2019. We have even more snowpack in the mountains than we did then, but the ground is warm enough to absorb water, and so far the weather has remained cool. If the weather warms slowly, we may avoid excessive runoff and flooding altogether. If, however, the weather warms quickly, we may experience high runoff and even flooding. We encourage residents in at-risk areas to prepare for that possibility.
Areas in the immediate vicinity of Box Elder Creek are at highest risk. You can visit FEMA's interactive map here to see if your property is in the floodway. Enter your address in the box at the top left. You may need to zoom in or out just a little bit to see the floodway layers fill in. Areas shaded with a red and blue stripe, referred to as FEMA Regulatory Floodway, are at highest risk. Areas shaded blue, together with the Floodway, are considered the 1% Annual Chance Flood Hazard area (formerly referred to as the 100-year flood risk area), and then the lower risk area is the tan, 0.2% Annual Chance Flood Hazard area.
If your property is not shaded at all, you are not located in the Floodway.
There are a number of steps you can take to mitigate potential flooding risk.
Beyond preparing your own home, we encourage residents to reach out to neighbors who may need some help to prepare their homes. In addition, please sign up for Brigham City's notification system and follow us on Facebook. We will use these inform residents about sudden changes in runoff conditions, emergency sandbag filling operations, and more. You may also consider registering for the Box Elder County Emergency Management Communication Alert System, CodeRED. You can download it from the Google Play Store or Apple Store, or sign up here.
If the flooding is beyond your ability to clean up, you should contact a disaster cleanup company.
The City has a plan in place to drop loads of sand and empty sandbags in central locations if flooding begins. Community members will be able to fill sandbags for their homes at that time. The City is not responsible to clean up personal property. However, Brigham City is full of good people who will undoubtedly work to help residents who experience flooding.
If you know the property owner, you should contact that person. If you don't know or are not able to reach the owner, or if the property is City-owned, contact non-emergency dispatch at 435-723-5227.
Brigham City Public Works crews have taken several steps to prepare for potential runoff, including drawing down the level of Mantua Reservoir to help control and capture high water flows, inspecting and cleaning storm drains, and clearing debris and obstructions out of the Box Elder Creek channel. Crews check several areas along the creek and in the drainage basin several times a day.
In addition, Public Works crews meet daily to discuss areas of concern and how to best address them. There are weekly flood management meetings with other City administrators to keep everyone informed and updated with new developments and progress.
The City has sandbags set aside to protect City infrastructure and others set aside for emergency response should flooding begin.
At this time, there is no emergency event, so our staff and community are in a preparation phase. It is the responsibility of property owners to take protective measures for their own property. Contrary to rumor, Brigham City has not received any state funding for flooding assistance at this point.
The City sells sandbags for $1 year-round. This charge covers the cost of the sandbag, the sand, and staffing at the compost facility.