Current Year compared to 2018

Gallatin County has received a record amount of snow in the past month for that period of time with the snow containing a near record amount of water.  However, the area isn’t too far off our average amount of winter precipitation for this time of the year (year to date).  We just received a large amount in a small period of time and there is more snow on that valley floor than we typically see at this time.  The graph to the right illustrates where we are now (black) compared to statistical medians and 2018 (orange).  So, will we flood?  We don’t know and really won’t have have a good indication until we see the weather for the next month.

Our area often sees heavy wet snow dumps in the spring and that is often a major contributor to spring runoff.  The big question with flooding is how quickly the snow melts in the mountains or valley floor.  Common situations that frequently expedite the snow melt are quick temperature shifts into the 70’s, mountains not dropping below freezing at night and significant warm rain over a short period of time.  When these factors align, we frequently see widespread flooding.  With the speed of the snow melting largely dependent on the weather over the next month and these contributing factors occurring, it is hard to say with certainty if we will or won’t be affected by widespread flooding.

The graph below indicates some recent large flood impact years with 2008 (orange), 2011 (purple) and 2019 (black).  While 2011 was a large impact to Montana, 2008 was the largest impact to Gallatin County in recent history where we experienced widespread flooding when the temperature turned hot and we experienced several days in a row of significant rainfall in the valley and mountains in May.  This release of water in a short period overwhelmed our waterways and resulted in flooding.  This rapid snow melt is indicated in the red box below.

Graph of 2008, 2011 & 2019 Years

What we do know is that somebody will be affected by isolated local flooding issues over the coming months.  Each year people are affected by isolated incidents where typically a ditch or culvert is blocked and water backs up.  Additionally, with the snow on the valley floor people will likely be affected by snow melting in yards where it flows towards the house and into a basement.  Now is the time for residents to help minimize the likelihood of being affected by localized water issues.  Residents are encouraged to do the following:

• Make sure ditches and culverts are clear of debris.
• Clear snow away from vents and basement windows.
• Ensure your snow has a path to melt and flow away from your house.

The key is that we want to make it as easy as possible for the water to flow away from your house!

More information of flood preparedness is available at: https://www.readygallatin.com/community-resources/preparedness-information/flooding-in-gallatin-county/

2008 Flooding

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As we move into spring the weather over the next 90 days will have a large impact on our spring runoff.  It is challenging in the middle of March to predict if we will get wet spring snow dumps, a quick spike in hot weather, or heavy warm rain – all of which impact how quickly our winter snow pack will melt off.  Ideally our snow will melt off continually over time, but when enough off these weather contributors occur the snow can melt faster than our waterways can accommodate and we see flooding.

At this point we can’t predict if flooding will occur, but we have a heavy snow pack on the valley floor and in the mountains.  If you live near a waterway, now is the time to make sure as much water as possible stays in the waterway.  Take some time now to do the following:

• Clean debris out of culverts and from under bridges.
• Clear debris out of ditches and other waterways.
• Make sure there is a clear path for snow to melt away from your buildings.
• Clear snow piles away from doors, windows and other places that makes it easy for melting snow to affect you.

Next, spend a few minutes to develop a plan on what you will do if flooding does affect you.

• Identify where you could be affected by flooding.
• Identify at what point the water would affect you, and develop a plan to keep the water from getting there.
• Identify what you would need in order to implement your plan and where you will get the supplies.  The best source for sand bags is Bozeman Brick and Tile on Jackrabbit.

If flooding does occur, do this:

• Closely monitor the water conditions and predicted weather.  Water levels change quickly and often peak in the middle of the night.
• If it looks like your plan may need to be implemented to protect your property, get the supplies and implement the plan.  Once flooding occurs, it is too late to prevent the damage.
• Once implemented, continue to monitor the situation and be prepared to make adjustments.  Water is hard to predict and it is going to go someplace.
• Be safe around flood water.  It can be very dangerous and often catches people off guard.

More information at:  https://www.readygallatin.com/community-resources/preparedness-information/flooding-in-gallatin-county/